Why can't I see bouncing of a switch on an oscilloscope?
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I'm trying to view the bouncing of a simple switch on an oscilloscope.
I have prepared a simple breadboard circuit (power->switch->resistor->ground). The problem is, it is displayed as a perfect square/rectangle on the scope. I have attached a photo of the scope screen and the circuit.
Please help me understand why I can't catch the bouncing of the switch on the scope. I don't think it this is a non-bouncing switch.
Edit: Here is a photo showing a zoomed-in time scale (50us/div). As you can see it is rising from 0V to 9V within 150us and staying there. I have tried a few different switches. The resistor in the picture is 220-Ohm, 0.5-Watt.
switches oscilloscope debounce
New contributor
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show 15 more comments
$begingroup$
I'm trying to view the bouncing of a simple switch on an oscilloscope.
I have prepared a simple breadboard circuit (power->switch->resistor->ground). The problem is, it is displayed as a perfect square/rectangle on the scope. I have attached a photo of the scope screen and the circuit.
Please help me understand why I can't catch the bouncing of the switch on the scope. I don't think it this is a non-bouncing switch.
Edit: Here is a photo showing a zoomed-in time scale (50us/div). As you can see it is rising from 0V to 9V within 150us and staying there. I have tried a few different switches. The resistor in the picture is 220-Ohm, 0.5-Watt.
switches oscilloscope debounce
New contributor
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9
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Have you tried adjusting the time base / horizontal scale?
$endgroup$
– NMF
6 hours ago
1
$begingroup$
If you don't succeed on the first try, try again.
$endgroup$
– StainlessSteelRat
6 hours ago
6
$begingroup$
I have a hard time believing that your zoomed in version is actually a new trig. Nothing would look like that except the scope's internal interpolation. An clean break with an RC-filter created by the scope would show an exponential clean rise - nothing linear. I bet that you just zoomed in on the stored waveform.
$endgroup$
– pipe
6 hours ago
1
$begingroup$
The slope is because of assorted capacitances in the system. Even though you are keeping things short, the wires, battery, breadboard, etc, will all have some small capacitances. However, I wouldn't expect to see such a linear rise. Perhaps, as mentioned, the scope is filtering the signal. Or perhaps not sampling fast enough to see it. Or perhaps (probably?) you need to take a new sample after you've zoomed in.
$endgroup$
– bitsmack
5 hours ago
2
$begingroup$
My zoomed photo is from another capture with battery instead of power supply. But as @pipe sait I have captured on zoomed out view and then zoomed on the rising edge after that. Now I understand that changing time scale before the capture and after the capture is different things? I didn't know that. I will need to figure out how to capture when time scale is set to uSec range.
$endgroup$
– Deniz
5 hours ago
|
show 15 more comments
$begingroup$
I'm trying to view the bouncing of a simple switch on an oscilloscope.
I have prepared a simple breadboard circuit (power->switch->resistor->ground). The problem is, it is displayed as a perfect square/rectangle on the scope. I have attached a photo of the scope screen and the circuit.
Please help me understand why I can't catch the bouncing of the switch on the scope. I don't think it this is a non-bouncing switch.
Edit: Here is a photo showing a zoomed-in time scale (50us/div). As you can see it is rising from 0V to 9V within 150us and staying there. I have tried a few different switches. The resistor in the picture is 220-Ohm, 0.5-Watt.
switches oscilloscope debounce
New contributor
$endgroup$
I'm trying to view the bouncing of a simple switch on an oscilloscope.
I have prepared a simple breadboard circuit (power->switch->resistor->ground). The problem is, it is displayed as a perfect square/rectangle on the scope. I have attached a photo of the scope screen and the circuit.
Please help me understand why I can't catch the bouncing of the switch on the scope. I don't think it this is a non-bouncing switch.
Edit: Here is a photo showing a zoomed-in time scale (50us/div). As you can see it is rising from 0V to 9V within 150us and staying there. I have tried a few different switches. The resistor in the picture is 220-Ohm, 0.5-Watt.
switches oscilloscope debounce
switches oscilloscope debounce
New contributor
New contributor
edited 12 mins ago
bitsmack
11.9k73677
11.9k73677
New contributor
asked 6 hours ago
DenizDeniz
1363
1363
New contributor
New contributor
9
$begingroup$
Have you tried adjusting the time base / horizontal scale?
$endgroup$
– NMF
6 hours ago
1
$begingroup$
If you don't succeed on the first try, try again.
$endgroup$
– StainlessSteelRat
6 hours ago
6
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I have a hard time believing that your zoomed in version is actually a new trig. Nothing would look like that except the scope's internal interpolation. An clean break with an RC-filter created by the scope would show an exponential clean rise - nothing linear. I bet that you just zoomed in on the stored waveform.
$endgroup$
– pipe
6 hours ago
1
$begingroup$
The slope is because of assorted capacitances in the system. Even though you are keeping things short, the wires, battery, breadboard, etc, will all have some small capacitances. However, I wouldn't expect to see such a linear rise. Perhaps, as mentioned, the scope is filtering the signal. Or perhaps not sampling fast enough to see it. Or perhaps (probably?) you need to take a new sample after you've zoomed in.
$endgroup$
– bitsmack
5 hours ago
2
$begingroup$
My zoomed photo is from another capture with battery instead of power supply. But as @pipe sait I have captured on zoomed out view and then zoomed on the rising edge after that. Now I understand that changing time scale before the capture and after the capture is different things? I didn't know that. I will need to figure out how to capture when time scale is set to uSec range.
$endgroup$
– Deniz
5 hours ago
|
show 15 more comments
9
$begingroup$
Have you tried adjusting the time base / horizontal scale?
$endgroup$
– NMF
6 hours ago
1
$begingroup$
If you don't succeed on the first try, try again.
$endgroup$
– StainlessSteelRat
6 hours ago
6
$begingroup$
I have a hard time believing that your zoomed in version is actually a new trig. Nothing would look like that except the scope's internal interpolation. An clean break with an RC-filter created by the scope would show an exponential clean rise - nothing linear. I bet that you just zoomed in on the stored waveform.
$endgroup$
– pipe
6 hours ago
1
$begingroup$
The slope is because of assorted capacitances in the system. Even though you are keeping things short, the wires, battery, breadboard, etc, will all have some small capacitances. However, I wouldn't expect to see such a linear rise. Perhaps, as mentioned, the scope is filtering the signal. Or perhaps not sampling fast enough to see it. Or perhaps (probably?) you need to take a new sample after you've zoomed in.
$endgroup$
– bitsmack
5 hours ago
2
$begingroup$
My zoomed photo is from another capture with battery instead of power supply. But as @pipe sait I have captured on zoomed out view and then zoomed on the rising edge after that. Now I understand that changing time scale before the capture and after the capture is different things? I didn't know that. I will need to figure out how to capture when time scale is set to uSec range.
$endgroup$
– Deniz
5 hours ago
9
9
$begingroup$
Have you tried adjusting the time base / horizontal scale?
$endgroup$
– NMF
6 hours ago
$begingroup$
Have you tried adjusting the time base / horizontal scale?
$endgroup$
– NMF
6 hours ago
1
1
$begingroup$
If you don't succeed on the first try, try again.
$endgroup$
– StainlessSteelRat
6 hours ago
$begingroup$
If you don't succeed on the first try, try again.
$endgroup$
– StainlessSteelRat
6 hours ago
6
6
$begingroup$
I have a hard time believing that your zoomed in version is actually a new trig. Nothing would look like that except the scope's internal interpolation. An clean break with an RC-filter created by the scope would show an exponential clean rise - nothing linear. I bet that you just zoomed in on the stored waveform.
$endgroup$
– pipe
6 hours ago
$begingroup$
I have a hard time believing that your zoomed in version is actually a new trig. Nothing would look like that except the scope's internal interpolation. An clean break with an RC-filter created by the scope would show an exponential clean rise - nothing linear. I bet that you just zoomed in on the stored waveform.
$endgroup$
– pipe
6 hours ago
1
1
$begingroup$
The slope is because of assorted capacitances in the system. Even though you are keeping things short, the wires, battery, breadboard, etc, will all have some small capacitances. However, I wouldn't expect to see such a linear rise. Perhaps, as mentioned, the scope is filtering the signal. Or perhaps not sampling fast enough to see it. Or perhaps (probably?) you need to take a new sample after you've zoomed in.
$endgroup$
– bitsmack
5 hours ago
$begingroup$
The slope is because of assorted capacitances in the system. Even though you are keeping things short, the wires, battery, breadboard, etc, will all have some small capacitances. However, I wouldn't expect to see such a linear rise. Perhaps, as mentioned, the scope is filtering the signal. Or perhaps not sampling fast enough to see it. Or perhaps (probably?) you need to take a new sample after you've zoomed in.
$endgroup$
– bitsmack
5 hours ago
2
2
$begingroup$
My zoomed photo is from another capture with battery instead of power supply. But as @pipe sait I have captured on zoomed out view and then zoomed on the rising edge after that. Now I understand that changing time scale before the capture and after the capture is different things? I didn't know that. I will need to figure out how to capture when time scale is set to uSec range.
$endgroup$
– Deniz
5 hours ago
$begingroup$
My zoomed photo is from another capture with battery instead of power supply. But as @pipe sait I have captured on zoomed out view and then zoomed on the rising edge after that. Now I understand that changing time scale before the capture and after the capture is different things? I didn't know that. I will need to figure out how to capture when time scale is set to uSec range.
$endgroup$
– Deniz
5 hours ago
|
show 15 more comments
7 Answers
7
active
oldest
votes
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First, "zoom in" to that rising edge by adjusting the time base. When you start getting close, you will start to see the rising slope of the signal.
As you do this, you will start to lose resolution on your captured signal. You can capture new samples of that rising edge using the scope's triggering mechanism.
Once you can see the rising slope, capture a new sample. Any bouncing/overshoot/noise should become apparent.
$endgroup$
$begingroup$
I have added 50uSec zoomed time scale photo. As you can see no bounce. I will also try to read button with a micro controller to see whether it is actually bouncing or not.
$endgroup$
– Deniz
6 hours ago
7
$begingroup$
If you zoom a stored waveform it may not have intermediate samples and just interpolate. You may see the edge sharper if you store a new sample at the higher timebase setting. As mentioned, good or new switches may have very little detectable bounce.
$endgroup$
– KalleMP
6 hours ago
3
$begingroup$
@Deniz no switch closure is going to result in a piecewise linear pulse -- that has to be a zoom-in of something sampled at a lower rate (probably 150$mu$s, because that's how long it's taking to rise up).
$endgroup$
– TimWescott
5 hours ago
add a comment |
$begingroup$
This is an issue with scope setup and misunderstanding of how to interpret scope captures. You must capture the rising edge of a single pulse at a reasonably small resolution by using a single trigger. Good news is that this is exactly what oscilloscopes are designed to do
The generic procedure is:
- Set trigger to edge (up) and trigger level at Approximately half scale of your button voltage
- (Optional) Move the trigger (horizontal) offset to the left hand of screen to maximize the portion of capture after trigger
- Switch trigger to "normal" and "single mode" to arm the trigger for a single capture
- Press your button
- If you use continuous trigger you will get a new capture with every button press
- If you don't use normal mode you may lose the captured signal due to preview refresh (typically triggered at 60hz to have a simulated "live signal" mode) , "single-normal" mode freezes the scope after capture
Most Digital capture scopes record a fixed number of points at all time base so the sample rate is determined by a combination of time base and capture depth (which may be configured) and limited by the maximum sampling rate. On my Tek the scope displays both the time per div and effective sample rate
What is displayed may also be "windowed" depending on mode so it may not always be clear what your sample rate actually is. For example 100K pts into 1s timebase with 10 divisions on screen would be 10ksps. 100k pts into 10us timebase with 10divisions on screen would be 1gsps, typically this is near the limit for common digital scopes so time bases below 10us are often "zoomed in" divisions at 10us (e.g. 100k pts into 10divisions at 10us, but display one division with 1us time base on screen)
Also note that analog bandwith (e..g "100Mhz ") does not directly related to the digital sample rate.
An additional quirk, triggering is not done on the (digital) sampled signal, but directly on the input through a dedicated trigger system. What this means is that you can trigger (sometimes) on a pulse that is too short to be resolved in the digital signal. Or you can add a trigger delay much much longer than the sample depth (e..g display the capture at 10us resolution but 1second after trigger) . This is also why there is often an "aux" or "external trigger" port that can be used to trigger but never displayed or captured
The scope is effectively sampling continuously into a ring buffer and the trigger comes along and tells the sampling systems to store the buffer. This is a large amount of data so it requires some time to store the data and to rearm the sample system. The electronics and suitable memory to process a gigabit stream continuously is very expensive so scopes are designed to make use of limited storage depth and digital bandwidth through triggering schemes
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+1! Much more informative than my answer :)
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– bitsmack
31 mins ago
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@bitsmack, thanks! Scopes are truly beautiful instruments
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– crasic
2 mins ago
add a comment |
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Figure 1. The guys down at photo-forensics found this.
There are several factors:
- You have a nice new clean switch that bounces very little.
- Your scope is loading the circuit and the 15 pF is enough to help. This is unlikely, though, with what appears to be a resistor with a value in the hundreds of ohms. (The colour rendition of your photo is poor.)
- Timebase is too fast - but your comments say you've checked this.
I'd go with the first and second option.
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I have added 50uSec zoomed time scale photo. As you can see no bounce. I will also try to read button with a micro controller to see whether it is actually bouncing or not.
$endgroup$
– Deniz
6 hours ago
2
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So you think the 15pF is loading the 220 Ohms with a 3.3ns RC asymptote resulting in a 150us linear ramp? Ask the forensic guys to check again. My forensic guy said it smelt like 220 ohm i.stack.imgur.com/xEwUo.png
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– Sunnyskyguy EE75
5 hours ago
add a comment |
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Assuming that the pull-down resistor is a reasonable value (1k - 10k), the very next thing that I would check is to see if there is a filter active on that channel. I wouldn't be looking for signal averaging - this is a single-event occurrence and the trace shows that single event. But it is entirely possible that there is a very-low frequency low-pass filter that is turned ON in the scope.
Another way to find out if it is a scope problem is to simply plug a pair of wires into the busses for the switch contacts. Then brush the two switch wires together and look at the noise (or lack thereof). Noise means scope is probably okay. Smooth ramp says that the scope isn't displaying the full bandwidth of the input signal.
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add a comment |
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use an old switch or store your new switch in a mixture of salt water and vinegar for a few hours, that will corrode the contacts and increase the bounce
New contributor
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add a comment |
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Why would it bounce upon switching? Have u any L or C in your circuit that would cause damping, or say bouncing? No bouncing in pure resistive circuits when switched on.
New contributor
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1
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This represents a fundamental misunderstanding of switches
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– Chris Stratton
1 hour ago
add a comment |
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I have gone thru the answers mentioned above.
But First, please change your oscilloscope.
The scope you are using would have a shallow memory.(Acquisition Memory ...may be 1K or a few K memory).
Try with Deep Memory Scopes.Tektronix TDS 3000 or 4000 series , Keysight DSOx 3000 to 6000 series or many more brands and models are available.
You will definitely get a beautiful contact bounce ringing at the top the vertical rising/ falling edges.
The number of ringing edges is proportional to the length of your grounding wire length.Less the length, less ringing.The more the length, more ringing.
The Deep Memory scopes will contain record length or Acquisition memory in terms of Mb ....say 2Mb , 4Mb, 8Mb etc......Don't worry about Sampling rates. Deep memory will control to sustain the sampling rate.
I have captured enough time these switching circuits,in Deep memory scopes.
Try ...
Best Regards
A Senthil
New contributor
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4
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The instrument in use is orders or magnitude more than sufficient if used properly. Recommending the purchase of new gear over learning to use the ordinary and suitable gear at hand is the mark of those who do not know what they are doing. There exists a capture rate, within the capability of that scope where the bouncing of the actual contacts is easily represented on the screen alone, nevermind any off-screen memory.
$endgroup$
– Chris Stratton
1 hour ago
add a comment |
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7 Answers
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7 Answers
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$begingroup$
First, "zoom in" to that rising edge by adjusting the time base. When you start getting close, you will start to see the rising slope of the signal.
As you do this, you will start to lose resolution on your captured signal. You can capture new samples of that rising edge using the scope's triggering mechanism.
Once you can see the rising slope, capture a new sample. Any bouncing/overshoot/noise should become apparent.
$endgroup$
$begingroup$
I have added 50uSec zoomed time scale photo. As you can see no bounce. I will also try to read button with a micro controller to see whether it is actually bouncing or not.
$endgroup$
– Deniz
6 hours ago
7
$begingroup$
If you zoom a stored waveform it may not have intermediate samples and just interpolate. You may see the edge sharper if you store a new sample at the higher timebase setting. As mentioned, good or new switches may have very little detectable bounce.
$endgroup$
– KalleMP
6 hours ago
3
$begingroup$
@Deniz no switch closure is going to result in a piecewise linear pulse -- that has to be a zoom-in of something sampled at a lower rate (probably 150$mu$s, because that's how long it's taking to rise up).
$endgroup$
– TimWescott
5 hours ago
add a comment |
$begingroup$
First, "zoom in" to that rising edge by adjusting the time base. When you start getting close, you will start to see the rising slope of the signal.
As you do this, you will start to lose resolution on your captured signal. You can capture new samples of that rising edge using the scope's triggering mechanism.
Once you can see the rising slope, capture a new sample. Any bouncing/overshoot/noise should become apparent.
$endgroup$
$begingroup$
I have added 50uSec zoomed time scale photo. As you can see no bounce. I will also try to read button with a micro controller to see whether it is actually bouncing or not.
$endgroup$
– Deniz
6 hours ago
7
$begingroup$
If you zoom a stored waveform it may not have intermediate samples and just interpolate. You may see the edge sharper if you store a new sample at the higher timebase setting. As mentioned, good or new switches may have very little detectable bounce.
$endgroup$
– KalleMP
6 hours ago
3
$begingroup$
@Deniz no switch closure is going to result in a piecewise linear pulse -- that has to be a zoom-in of something sampled at a lower rate (probably 150$mu$s, because that's how long it's taking to rise up).
$endgroup$
– TimWescott
5 hours ago
add a comment |
$begingroup$
First, "zoom in" to that rising edge by adjusting the time base. When you start getting close, you will start to see the rising slope of the signal.
As you do this, you will start to lose resolution on your captured signal. You can capture new samples of that rising edge using the scope's triggering mechanism.
Once you can see the rising slope, capture a new sample. Any bouncing/overshoot/noise should become apparent.
$endgroup$
First, "zoom in" to that rising edge by adjusting the time base. When you start getting close, you will start to see the rising slope of the signal.
As you do this, you will start to lose resolution on your captured signal. You can capture new samples of that rising edge using the scope's triggering mechanism.
Once you can see the rising slope, capture a new sample. Any bouncing/overshoot/noise should become apparent.
edited 5 hours ago
answered 6 hours ago
bitsmackbitsmack
11.9k73677
11.9k73677
$begingroup$
I have added 50uSec zoomed time scale photo. As you can see no bounce. I will also try to read button with a micro controller to see whether it is actually bouncing or not.
$endgroup$
– Deniz
6 hours ago
7
$begingroup$
If you zoom a stored waveform it may not have intermediate samples and just interpolate. You may see the edge sharper if you store a new sample at the higher timebase setting. As mentioned, good or new switches may have very little detectable bounce.
$endgroup$
– KalleMP
6 hours ago
3
$begingroup$
@Deniz no switch closure is going to result in a piecewise linear pulse -- that has to be a zoom-in of something sampled at a lower rate (probably 150$mu$s, because that's how long it's taking to rise up).
$endgroup$
– TimWescott
5 hours ago
add a comment |
$begingroup$
I have added 50uSec zoomed time scale photo. As you can see no bounce. I will also try to read button with a micro controller to see whether it is actually bouncing or not.
$endgroup$
– Deniz
6 hours ago
7
$begingroup$
If you zoom a stored waveform it may not have intermediate samples and just interpolate. You may see the edge sharper if you store a new sample at the higher timebase setting. As mentioned, good or new switches may have very little detectable bounce.
$endgroup$
– KalleMP
6 hours ago
3
$begingroup$
@Deniz no switch closure is going to result in a piecewise linear pulse -- that has to be a zoom-in of something sampled at a lower rate (probably 150$mu$s, because that's how long it's taking to rise up).
$endgroup$
– TimWescott
5 hours ago
$begingroup$
I have added 50uSec zoomed time scale photo. As you can see no bounce. I will also try to read button with a micro controller to see whether it is actually bouncing or not.
$endgroup$
– Deniz
6 hours ago
$begingroup$
I have added 50uSec zoomed time scale photo. As you can see no bounce. I will also try to read button with a micro controller to see whether it is actually bouncing or not.
$endgroup$
– Deniz
6 hours ago
7
7
$begingroup$
If you zoom a stored waveform it may not have intermediate samples and just interpolate. You may see the edge sharper if you store a new sample at the higher timebase setting. As mentioned, good or new switches may have very little detectable bounce.
$endgroup$
– KalleMP
6 hours ago
$begingroup$
If you zoom a stored waveform it may not have intermediate samples and just interpolate. You may see the edge sharper if you store a new sample at the higher timebase setting. As mentioned, good or new switches may have very little detectable bounce.
$endgroup$
– KalleMP
6 hours ago
3
3
$begingroup$
@Deniz no switch closure is going to result in a piecewise linear pulse -- that has to be a zoom-in of something sampled at a lower rate (probably 150$mu$s, because that's how long it's taking to rise up).
$endgroup$
– TimWescott
5 hours ago
$begingroup$
@Deniz no switch closure is going to result in a piecewise linear pulse -- that has to be a zoom-in of something sampled at a lower rate (probably 150$mu$s, because that's how long it's taking to rise up).
$endgroup$
– TimWescott
5 hours ago
add a comment |
$begingroup$
This is an issue with scope setup and misunderstanding of how to interpret scope captures. You must capture the rising edge of a single pulse at a reasonably small resolution by using a single trigger. Good news is that this is exactly what oscilloscopes are designed to do
The generic procedure is:
- Set trigger to edge (up) and trigger level at Approximately half scale of your button voltage
- (Optional) Move the trigger (horizontal) offset to the left hand of screen to maximize the portion of capture after trigger
- Switch trigger to "normal" and "single mode" to arm the trigger for a single capture
- Press your button
- If you use continuous trigger you will get a new capture with every button press
- If you don't use normal mode you may lose the captured signal due to preview refresh (typically triggered at 60hz to have a simulated "live signal" mode) , "single-normal" mode freezes the scope after capture
Most Digital capture scopes record a fixed number of points at all time base so the sample rate is determined by a combination of time base and capture depth (which may be configured) and limited by the maximum sampling rate. On my Tek the scope displays both the time per div and effective sample rate
What is displayed may also be "windowed" depending on mode so it may not always be clear what your sample rate actually is. For example 100K pts into 1s timebase with 10 divisions on screen would be 10ksps. 100k pts into 10us timebase with 10divisions on screen would be 1gsps, typically this is near the limit for common digital scopes so time bases below 10us are often "zoomed in" divisions at 10us (e.g. 100k pts into 10divisions at 10us, but display one division with 1us time base on screen)
Also note that analog bandwith (e..g "100Mhz ") does not directly related to the digital sample rate.
An additional quirk, triggering is not done on the (digital) sampled signal, but directly on the input through a dedicated trigger system. What this means is that you can trigger (sometimes) on a pulse that is too short to be resolved in the digital signal. Or you can add a trigger delay much much longer than the sample depth (e..g display the capture at 10us resolution but 1second after trigger) . This is also why there is often an "aux" or "external trigger" port that can be used to trigger but never displayed or captured
The scope is effectively sampling continuously into a ring buffer and the trigger comes along and tells the sampling systems to store the buffer. This is a large amount of data so it requires some time to store the data and to rearm the sample system. The electronics and suitable memory to process a gigabit stream continuously is very expensive so scopes are designed to make use of limited storage depth and digital bandwidth through triggering schemes
$endgroup$
$begingroup$
+1! Much more informative than my answer :)
$endgroup$
– bitsmack
31 mins ago
$begingroup$
@bitsmack, thanks! Scopes are truly beautiful instruments
$endgroup$
– crasic
2 mins ago
add a comment |
$begingroup$
This is an issue with scope setup and misunderstanding of how to interpret scope captures. You must capture the rising edge of a single pulse at a reasonably small resolution by using a single trigger. Good news is that this is exactly what oscilloscopes are designed to do
The generic procedure is:
- Set trigger to edge (up) and trigger level at Approximately half scale of your button voltage
- (Optional) Move the trigger (horizontal) offset to the left hand of screen to maximize the portion of capture after trigger
- Switch trigger to "normal" and "single mode" to arm the trigger for a single capture
- Press your button
- If you use continuous trigger you will get a new capture with every button press
- If you don't use normal mode you may lose the captured signal due to preview refresh (typically triggered at 60hz to have a simulated "live signal" mode) , "single-normal" mode freezes the scope after capture
Most Digital capture scopes record a fixed number of points at all time base so the sample rate is determined by a combination of time base and capture depth (which may be configured) and limited by the maximum sampling rate. On my Tek the scope displays both the time per div and effective sample rate
What is displayed may also be "windowed" depending on mode so it may not always be clear what your sample rate actually is. For example 100K pts into 1s timebase with 10 divisions on screen would be 10ksps. 100k pts into 10us timebase with 10divisions on screen would be 1gsps, typically this is near the limit for common digital scopes so time bases below 10us are often "zoomed in" divisions at 10us (e.g. 100k pts into 10divisions at 10us, but display one division with 1us time base on screen)
Also note that analog bandwith (e..g "100Mhz ") does not directly related to the digital sample rate.
An additional quirk, triggering is not done on the (digital) sampled signal, but directly on the input through a dedicated trigger system. What this means is that you can trigger (sometimes) on a pulse that is too short to be resolved in the digital signal. Or you can add a trigger delay much much longer than the sample depth (e..g display the capture at 10us resolution but 1second after trigger) . This is also why there is often an "aux" or "external trigger" port that can be used to trigger but never displayed or captured
The scope is effectively sampling continuously into a ring buffer and the trigger comes along and tells the sampling systems to store the buffer. This is a large amount of data so it requires some time to store the data and to rearm the sample system. The electronics and suitable memory to process a gigabit stream continuously is very expensive so scopes are designed to make use of limited storage depth and digital bandwidth through triggering schemes
$endgroup$
$begingroup$
+1! Much more informative than my answer :)
$endgroup$
– bitsmack
31 mins ago
$begingroup$
@bitsmack, thanks! Scopes are truly beautiful instruments
$endgroup$
– crasic
2 mins ago
add a comment |
$begingroup$
This is an issue with scope setup and misunderstanding of how to interpret scope captures. You must capture the rising edge of a single pulse at a reasonably small resolution by using a single trigger. Good news is that this is exactly what oscilloscopes are designed to do
The generic procedure is:
- Set trigger to edge (up) and trigger level at Approximately half scale of your button voltage
- (Optional) Move the trigger (horizontal) offset to the left hand of screen to maximize the portion of capture after trigger
- Switch trigger to "normal" and "single mode" to arm the trigger for a single capture
- Press your button
- If you use continuous trigger you will get a new capture with every button press
- If you don't use normal mode you may lose the captured signal due to preview refresh (typically triggered at 60hz to have a simulated "live signal" mode) , "single-normal" mode freezes the scope after capture
Most Digital capture scopes record a fixed number of points at all time base so the sample rate is determined by a combination of time base and capture depth (which may be configured) and limited by the maximum sampling rate. On my Tek the scope displays both the time per div and effective sample rate
What is displayed may also be "windowed" depending on mode so it may not always be clear what your sample rate actually is. For example 100K pts into 1s timebase with 10 divisions on screen would be 10ksps. 100k pts into 10us timebase with 10divisions on screen would be 1gsps, typically this is near the limit for common digital scopes so time bases below 10us are often "zoomed in" divisions at 10us (e.g. 100k pts into 10divisions at 10us, but display one division with 1us time base on screen)
Also note that analog bandwith (e..g "100Mhz ") does not directly related to the digital sample rate.
An additional quirk, triggering is not done on the (digital) sampled signal, but directly on the input through a dedicated trigger system. What this means is that you can trigger (sometimes) on a pulse that is too short to be resolved in the digital signal. Or you can add a trigger delay much much longer than the sample depth (e..g display the capture at 10us resolution but 1second after trigger) . This is also why there is often an "aux" or "external trigger" port that can be used to trigger but never displayed or captured
The scope is effectively sampling continuously into a ring buffer and the trigger comes along and tells the sampling systems to store the buffer. This is a large amount of data so it requires some time to store the data and to rearm the sample system. The electronics and suitable memory to process a gigabit stream continuously is very expensive so scopes are designed to make use of limited storage depth and digital bandwidth through triggering schemes
$endgroup$
This is an issue with scope setup and misunderstanding of how to interpret scope captures. You must capture the rising edge of a single pulse at a reasonably small resolution by using a single trigger. Good news is that this is exactly what oscilloscopes are designed to do
The generic procedure is:
- Set trigger to edge (up) and trigger level at Approximately half scale of your button voltage
- (Optional) Move the trigger (horizontal) offset to the left hand of screen to maximize the portion of capture after trigger
- Switch trigger to "normal" and "single mode" to arm the trigger for a single capture
- Press your button
- If you use continuous trigger you will get a new capture with every button press
- If you don't use normal mode you may lose the captured signal due to preview refresh (typically triggered at 60hz to have a simulated "live signal" mode) , "single-normal" mode freezes the scope after capture
Most Digital capture scopes record a fixed number of points at all time base so the sample rate is determined by a combination of time base and capture depth (which may be configured) and limited by the maximum sampling rate. On my Tek the scope displays both the time per div and effective sample rate
What is displayed may also be "windowed" depending on mode so it may not always be clear what your sample rate actually is. For example 100K pts into 1s timebase with 10 divisions on screen would be 10ksps. 100k pts into 10us timebase with 10divisions on screen would be 1gsps, typically this is near the limit for common digital scopes so time bases below 10us are often "zoomed in" divisions at 10us (e.g. 100k pts into 10divisions at 10us, but display one division with 1us time base on screen)
Also note that analog bandwith (e..g "100Mhz ") does not directly related to the digital sample rate.
An additional quirk, triggering is not done on the (digital) sampled signal, but directly on the input through a dedicated trigger system. What this means is that you can trigger (sometimes) on a pulse that is too short to be resolved in the digital signal. Or you can add a trigger delay much much longer than the sample depth (e..g display the capture at 10us resolution but 1second after trigger) . This is also why there is often an "aux" or "external trigger" port that can be used to trigger but never displayed or captured
The scope is effectively sampling continuously into a ring buffer and the trigger comes along and tells the sampling systems to store the buffer. This is a large amount of data so it requires some time to store the data and to rearm the sample system. The electronics and suitable memory to process a gigabit stream continuously is very expensive so scopes are designed to make use of limited storage depth and digital bandwidth through triggering schemes
edited 3 hours ago
answered 3 hours ago
crasiccrasic
3,084926
3,084926
$begingroup$
+1! Much more informative than my answer :)
$endgroup$
– bitsmack
31 mins ago
$begingroup$
@bitsmack, thanks! Scopes are truly beautiful instruments
$endgroup$
– crasic
2 mins ago
add a comment |
$begingroup$
+1! Much more informative than my answer :)
$endgroup$
– bitsmack
31 mins ago
$begingroup$
@bitsmack, thanks! Scopes are truly beautiful instruments
$endgroup$
– crasic
2 mins ago
$begingroup$
+1! Much more informative than my answer :)
$endgroup$
– bitsmack
31 mins ago
$begingroup$
+1! Much more informative than my answer :)
$endgroup$
– bitsmack
31 mins ago
$begingroup$
@bitsmack, thanks! Scopes are truly beautiful instruments
$endgroup$
– crasic
2 mins ago
$begingroup$
@bitsmack, thanks! Scopes are truly beautiful instruments
$endgroup$
– crasic
2 mins ago
add a comment |
$begingroup$
Figure 1. The guys down at photo-forensics found this.
There are several factors:
- You have a nice new clean switch that bounces very little.
- Your scope is loading the circuit and the 15 pF is enough to help. This is unlikely, though, with what appears to be a resistor with a value in the hundreds of ohms. (The colour rendition of your photo is poor.)
- Timebase is too fast - but your comments say you've checked this.
I'd go with the first and second option.
$endgroup$
$begingroup$
I have added 50uSec zoomed time scale photo. As you can see no bounce. I will also try to read button with a micro controller to see whether it is actually bouncing or not.
$endgroup$
– Deniz
6 hours ago
2
$begingroup$
So you think the 15pF is loading the 220 Ohms with a 3.3ns RC asymptote resulting in a 150us linear ramp? Ask the forensic guys to check again. My forensic guy said it smelt like 220 ohm i.stack.imgur.com/xEwUo.png
$endgroup$
– Sunnyskyguy EE75
5 hours ago
add a comment |
$begingroup$
Figure 1. The guys down at photo-forensics found this.
There are several factors:
- You have a nice new clean switch that bounces very little.
- Your scope is loading the circuit and the 15 pF is enough to help. This is unlikely, though, with what appears to be a resistor with a value in the hundreds of ohms. (The colour rendition of your photo is poor.)
- Timebase is too fast - but your comments say you've checked this.
I'd go with the first and second option.
$endgroup$
$begingroup$
I have added 50uSec zoomed time scale photo. As you can see no bounce. I will also try to read button with a micro controller to see whether it is actually bouncing or not.
$endgroup$
– Deniz
6 hours ago
2
$begingroup$
So you think the 15pF is loading the 220 Ohms with a 3.3ns RC asymptote resulting in a 150us linear ramp? Ask the forensic guys to check again. My forensic guy said it smelt like 220 ohm i.stack.imgur.com/xEwUo.png
$endgroup$
– Sunnyskyguy EE75
5 hours ago
add a comment |
$begingroup$
Figure 1. The guys down at photo-forensics found this.
There are several factors:
- You have a nice new clean switch that bounces very little.
- Your scope is loading the circuit and the 15 pF is enough to help. This is unlikely, though, with what appears to be a resistor with a value in the hundreds of ohms. (The colour rendition of your photo is poor.)
- Timebase is too fast - but your comments say you've checked this.
I'd go with the first and second option.
$endgroup$
Figure 1. The guys down at photo-forensics found this.
There are several factors:
- You have a nice new clean switch that bounces very little.
- Your scope is loading the circuit and the 15 pF is enough to help. This is unlikely, though, with what appears to be a resistor with a value in the hundreds of ohms. (The colour rendition of your photo is poor.)
- Timebase is too fast - but your comments say you've checked this.
I'd go with the first and second option.
answered 6 hours ago
TransistorTransistor
88.2k785189
88.2k785189
$begingroup$
I have added 50uSec zoomed time scale photo. As you can see no bounce. I will also try to read button with a micro controller to see whether it is actually bouncing or not.
$endgroup$
– Deniz
6 hours ago
2
$begingroup$
So you think the 15pF is loading the 220 Ohms with a 3.3ns RC asymptote resulting in a 150us linear ramp? Ask the forensic guys to check again. My forensic guy said it smelt like 220 ohm i.stack.imgur.com/xEwUo.png
$endgroup$
– Sunnyskyguy EE75
5 hours ago
add a comment |
$begingroup$
I have added 50uSec zoomed time scale photo. As you can see no bounce. I will also try to read button with a micro controller to see whether it is actually bouncing or not.
$endgroup$
– Deniz
6 hours ago
2
$begingroup$
So you think the 15pF is loading the 220 Ohms with a 3.3ns RC asymptote resulting in a 150us linear ramp? Ask the forensic guys to check again. My forensic guy said it smelt like 220 ohm i.stack.imgur.com/xEwUo.png
$endgroup$
– Sunnyskyguy EE75
5 hours ago
$begingroup$
I have added 50uSec zoomed time scale photo. As you can see no bounce. I will also try to read button with a micro controller to see whether it is actually bouncing or not.
$endgroup$
– Deniz
6 hours ago
$begingroup$
I have added 50uSec zoomed time scale photo. As you can see no bounce. I will also try to read button with a micro controller to see whether it is actually bouncing or not.
$endgroup$
– Deniz
6 hours ago
2
2
$begingroup$
So you think the 15pF is loading the 220 Ohms with a 3.3ns RC asymptote resulting in a 150us linear ramp? Ask the forensic guys to check again. My forensic guy said it smelt like 220 ohm i.stack.imgur.com/xEwUo.png
$endgroup$
– Sunnyskyguy EE75
5 hours ago
$begingroup$
So you think the 15pF is loading the 220 Ohms with a 3.3ns RC asymptote resulting in a 150us linear ramp? Ask the forensic guys to check again. My forensic guy said it smelt like 220 ohm i.stack.imgur.com/xEwUo.png
$endgroup$
– Sunnyskyguy EE75
5 hours ago
add a comment |
$begingroup$
Assuming that the pull-down resistor is a reasonable value (1k - 10k), the very next thing that I would check is to see if there is a filter active on that channel. I wouldn't be looking for signal averaging - this is a single-event occurrence and the trace shows that single event. But it is entirely possible that there is a very-low frequency low-pass filter that is turned ON in the scope.
Another way to find out if it is a scope problem is to simply plug a pair of wires into the busses for the switch contacts. Then brush the two switch wires together and look at the noise (or lack thereof). Noise means scope is probably okay. Smooth ramp says that the scope isn't displaying the full bandwidth of the input signal.
$endgroup$
add a comment |
$begingroup$
Assuming that the pull-down resistor is a reasonable value (1k - 10k), the very next thing that I would check is to see if there is a filter active on that channel. I wouldn't be looking for signal averaging - this is a single-event occurrence and the trace shows that single event. But it is entirely possible that there is a very-low frequency low-pass filter that is turned ON in the scope.
Another way to find out if it is a scope problem is to simply plug a pair of wires into the busses for the switch contacts. Then brush the two switch wires together and look at the noise (or lack thereof). Noise means scope is probably okay. Smooth ramp says that the scope isn't displaying the full bandwidth of the input signal.
$endgroup$
add a comment |
$begingroup$
Assuming that the pull-down resistor is a reasonable value (1k - 10k), the very next thing that I would check is to see if there is a filter active on that channel. I wouldn't be looking for signal averaging - this is a single-event occurrence and the trace shows that single event. But it is entirely possible that there is a very-low frequency low-pass filter that is turned ON in the scope.
Another way to find out if it is a scope problem is to simply plug a pair of wires into the busses for the switch contacts. Then brush the two switch wires together and look at the noise (or lack thereof). Noise means scope is probably okay. Smooth ramp says that the scope isn't displaying the full bandwidth of the input signal.
$endgroup$
Assuming that the pull-down resistor is a reasonable value (1k - 10k), the very next thing that I would check is to see if there is a filter active on that channel. I wouldn't be looking for signal averaging - this is a single-event occurrence and the trace shows that single event. But it is entirely possible that there is a very-low frequency low-pass filter that is turned ON in the scope.
Another way to find out if it is a scope problem is to simply plug a pair of wires into the busses for the switch contacts. Then brush the two switch wires together and look at the noise (or lack thereof). Noise means scope is probably okay. Smooth ramp says that the scope isn't displaying the full bandwidth of the input signal.
answered 3 hours ago
Dwayne ReidDwayne Reid
18.1k21949
18.1k21949
add a comment |
add a comment |
$begingroup$
use an old switch or store your new switch in a mixture of salt water and vinegar for a few hours, that will corrode the contacts and increase the bounce
New contributor
$endgroup$
add a comment |
$begingroup$
use an old switch or store your new switch in a mixture of salt water and vinegar for a few hours, that will corrode the contacts and increase the bounce
New contributor
$endgroup$
add a comment |
$begingroup$
use an old switch or store your new switch in a mixture of salt water and vinegar for a few hours, that will corrode the contacts and increase the bounce
New contributor
$endgroup$
use an old switch or store your new switch in a mixture of salt water and vinegar for a few hours, that will corrode the contacts and increase the bounce
New contributor
New contributor
answered 1 hour ago
ronron
1
1
New contributor
New contributor
add a comment |
add a comment |
$begingroup$
Why would it bounce upon switching? Have u any L or C in your circuit that would cause damping, or say bouncing? No bouncing in pure resistive circuits when switched on.
New contributor
$endgroup$
1
$begingroup$
This represents a fundamental misunderstanding of switches
$endgroup$
– Chris Stratton
1 hour ago
add a comment |
$begingroup$
Why would it bounce upon switching? Have u any L or C in your circuit that would cause damping, or say bouncing? No bouncing in pure resistive circuits when switched on.
New contributor
$endgroup$
1
$begingroup$
This represents a fundamental misunderstanding of switches
$endgroup$
– Chris Stratton
1 hour ago
add a comment |
$begingroup$
Why would it bounce upon switching? Have u any L or C in your circuit that would cause damping, or say bouncing? No bouncing in pure resistive circuits when switched on.
New contributor
$endgroup$
Why would it bounce upon switching? Have u any L or C in your circuit that would cause damping, or say bouncing? No bouncing in pure resistive circuits when switched on.
New contributor
New contributor
answered 1 hour ago
HAMOOD UR REHMANHAMOOD UR REHMAN
1
1
New contributor
New contributor
1
$begingroup$
This represents a fundamental misunderstanding of switches
$endgroup$
– Chris Stratton
1 hour ago
add a comment |
1
$begingroup$
This represents a fundamental misunderstanding of switches
$endgroup$
– Chris Stratton
1 hour ago
1
1
$begingroup$
This represents a fundamental misunderstanding of switches
$endgroup$
– Chris Stratton
1 hour ago
$begingroup$
This represents a fundamental misunderstanding of switches
$endgroup$
– Chris Stratton
1 hour ago
add a comment |
$begingroup$
I have gone thru the answers mentioned above.
But First, please change your oscilloscope.
The scope you are using would have a shallow memory.(Acquisition Memory ...may be 1K or a few K memory).
Try with Deep Memory Scopes.Tektronix TDS 3000 or 4000 series , Keysight DSOx 3000 to 6000 series or many more brands and models are available.
You will definitely get a beautiful contact bounce ringing at the top the vertical rising/ falling edges.
The number of ringing edges is proportional to the length of your grounding wire length.Less the length, less ringing.The more the length, more ringing.
The Deep Memory scopes will contain record length or Acquisition memory in terms of Mb ....say 2Mb , 4Mb, 8Mb etc......Don't worry about Sampling rates. Deep memory will control to sustain the sampling rate.
I have captured enough time these switching circuits,in Deep memory scopes.
Try ...
Best Regards
A Senthil
New contributor
$endgroup$
4
$begingroup$
The instrument in use is orders or magnitude more than sufficient if used properly. Recommending the purchase of new gear over learning to use the ordinary and suitable gear at hand is the mark of those who do not know what they are doing. There exists a capture rate, within the capability of that scope where the bouncing of the actual contacts is easily represented on the screen alone, nevermind any off-screen memory.
$endgroup$
– Chris Stratton
1 hour ago
add a comment |
$begingroup$
I have gone thru the answers mentioned above.
But First, please change your oscilloscope.
The scope you are using would have a shallow memory.(Acquisition Memory ...may be 1K or a few K memory).
Try with Deep Memory Scopes.Tektronix TDS 3000 or 4000 series , Keysight DSOx 3000 to 6000 series or many more brands and models are available.
You will definitely get a beautiful contact bounce ringing at the top the vertical rising/ falling edges.
The number of ringing edges is proportional to the length of your grounding wire length.Less the length, less ringing.The more the length, more ringing.
The Deep Memory scopes will contain record length or Acquisition memory in terms of Mb ....say 2Mb , 4Mb, 8Mb etc......Don't worry about Sampling rates. Deep memory will control to sustain the sampling rate.
I have captured enough time these switching circuits,in Deep memory scopes.
Try ...
Best Regards
A Senthil
New contributor
$endgroup$
4
$begingroup$
The instrument in use is orders or magnitude more than sufficient if used properly. Recommending the purchase of new gear over learning to use the ordinary and suitable gear at hand is the mark of those who do not know what they are doing. There exists a capture rate, within the capability of that scope where the bouncing of the actual contacts is easily represented on the screen alone, nevermind any off-screen memory.
$endgroup$
– Chris Stratton
1 hour ago
add a comment |
$begingroup$
I have gone thru the answers mentioned above.
But First, please change your oscilloscope.
The scope you are using would have a shallow memory.(Acquisition Memory ...may be 1K or a few K memory).
Try with Deep Memory Scopes.Tektronix TDS 3000 or 4000 series , Keysight DSOx 3000 to 6000 series or many more brands and models are available.
You will definitely get a beautiful contact bounce ringing at the top the vertical rising/ falling edges.
The number of ringing edges is proportional to the length of your grounding wire length.Less the length, less ringing.The more the length, more ringing.
The Deep Memory scopes will contain record length or Acquisition memory in terms of Mb ....say 2Mb , 4Mb, 8Mb etc......Don't worry about Sampling rates. Deep memory will control to sustain the sampling rate.
I have captured enough time these switching circuits,in Deep memory scopes.
Try ...
Best Regards
A Senthil
New contributor
$endgroup$
I have gone thru the answers mentioned above.
But First, please change your oscilloscope.
The scope you are using would have a shallow memory.(Acquisition Memory ...may be 1K or a few K memory).
Try with Deep Memory Scopes.Tektronix TDS 3000 or 4000 series , Keysight DSOx 3000 to 6000 series or many more brands and models are available.
You will definitely get a beautiful contact bounce ringing at the top the vertical rising/ falling edges.
The number of ringing edges is proportional to the length of your grounding wire length.Less the length, less ringing.The more the length, more ringing.
The Deep Memory scopes will contain record length or Acquisition memory in terms of Mb ....say 2Mb , 4Mb, 8Mb etc......Don't worry about Sampling rates. Deep memory will control to sustain the sampling rate.
I have captured enough time these switching circuits,in Deep memory scopes.
Try ...
Best Regards
A Senthil
New contributor
New contributor
answered 1 hour ago
A SenthilA Senthil
1
1
New contributor
New contributor
4
$begingroup$
The instrument in use is orders or magnitude more than sufficient if used properly. Recommending the purchase of new gear over learning to use the ordinary and suitable gear at hand is the mark of those who do not know what they are doing. There exists a capture rate, within the capability of that scope where the bouncing of the actual contacts is easily represented on the screen alone, nevermind any off-screen memory.
$endgroup$
– Chris Stratton
1 hour ago
add a comment |
4
$begingroup$
The instrument in use is orders or magnitude more than sufficient if used properly. Recommending the purchase of new gear over learning to use the ordinary and suitable gear at hand is the mark of those who do not know what they are doing. There exists a capture rate, within the capability of that scope where the bouncing of the actual contacts is easily represented on the screen alone, nevermind any off-screen memory.
$endgroup$
– Chris Stratton
1 hour ago
4
4
$begingroup$
The instrument in use is orders or magnitude more than sufficient if used properly. Recommending the purchase of new gear over learning to use the ordinary and suitable gear at hand is the mark of those who do not know what they are doing. There exists a capture rate, within the capability of that scope where the bouncing of the actual contacts is easily represented on the screen alone, nevermind any off-screen memory.
$endgroup$
– Chris Stratton
1 hour ago
$begingroup$
The instrument in use is orders or magnitude more than sufficient if used properly. Recommending the purchase of new gear over learning to use the ordinary and suitable gear at hand is the mark of those who do not know what they are doing. There exists a capture rate, within the capability of that scope where the bouncing of the actual contacts is easily represented on the screen alone, nevermind any off-screen memory.
$endgroup$
– Chris Stratton
1 hour ago
add a comment |
Deniz is a new contributor. Be nice, and check out our Code of Conduct.
Deniz is a new contributor. Be nice, and check out our Code of Conduct.
Deniz is a new contributor. Be nice, and check out our Code of Conduct.
Deniz is a new contributor. Be nice, and check out our Code of Conduct.
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Have you tried adjusting the time base / horizontal scale?
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– NMF
6 hours ago
1
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If you don't succeed on the first try, try again.
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– StainlessSteelRat
6 hours ago
6
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I have a hard time believing that your zoomed in version is actually a new trig. Nothing would look like that except the scope's internal interpolation. An clean break with an RC-filter created by the scope would show an exponential clean rise - nothing linear. I bet that you just zoomed in on the stored waveform.
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– pipe
6 hours ago
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The slope is because of assorted capacitances in the system. Even though you are keeping things short, the wires, battery, breadboard, etc, will all have some small capacitances. However, I wouldn't expect to see such a linear rise. Perhaps, as mentioned, the scope is filtering the signal. Or perhaps not sampling fast enough to see it. Or perhaps (probably?) you need to take a new sample after you've zoomed in.
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– bitsmack
5 hours ago
2
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My zoomed photo is from another capture with battery instead of power supply. But as @pipe sait I have captured on zoomed out view and then zoomed on the rising edge after that. Now I understand that changing time scale before the capture and after the capture is different things? I didn't know that. I will need to figure out how to capture when time scale is set to uSec range.
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– Deniz
5 hours ago