Check Oscilloscope input integrity - Siglent 1104X-E

[Satangoss]

Hello everybody,

I would like to ask you experienced guys how do I know if my Oscilloscope inputs are working properly.

I was measuring DC signals around 6V coming from a stepper driver using channel 1 in coil A and channel 2 in coil B.
I realized after the first measurement that the voltage/division in the scope channels 1 and 2 was set to 500mV and both the probes and the scope were set to gain 1X. Now I am concerned whether or not that could have cause a damage in the scope inputs.
It seems it is working, but how do I know there was no damage to the inputs? How can I check the inputs integrity?
The scope is for hobby, but still, how can I be confident it is measuring properly now?

I looked in the Siglent datasheet for input protection or something similar and I didn't find anything that could give me a clue in this direction.

Thank you in advance.

[bdunham7]

The inputs are rated for 400 volts peak, as stated right on the front near the BNC connectors.  I wouldn't push that limit, but 6V plus some inductive kick from a stepper motor shouldn't bother it at all.

You can check your scope easily by going into the UTILITY menu and selecting SELF CAL.  Remove all input cables and run the self-calibration routine, if it passes that it is 99.9% likely to be OK.

[David Hess]

The input protection specifications apply at all vertical sensitivity settings so there should have been no damage.

The most common subtle damage is excessive leakage current which will cause a DC offset.  To check this, use the most sensitive vertical sensitivity setting and look for a change in DC level between having the input open and the input shorted.  A 50 ohm termination works fine as a short.

[tautech]

Hello everybody,

I would like to ask you experienced guys how do I know if my Oscilloscope inputs are working properly.

Welcome to the forum.

Quickest sanity check is the probe compensation output. Period.
1 KHz @ ~3.2V.

Self Cal will pick up any deeper issues but it takes 5-10 minutes to complete.

[Satangoss]

Thank you for the explanation and the recommendation bdunham7. 

I run a self calibration and that ended up ok without any warning messages. (Not sure whether there would be some in case of problems, I guess so).

[Satangoss]

The input protection specifications apply at all vertical sensitivity settings so there should have been no damage.

The most common subtle damage is excessive leakage current which will cause a DC offset.  To check this, use the most sensitive vertical sensitivity setting and look for a change in DC level between having the input open and the input shorted.  A 50 ohm termination works fine as a short.

Hi David,

First thank you for your time and advice. Apologize for my ignorance, but to be sure how do I do that? Just place a 50 Ohm resistor shorting the probe ground terminal the probing tip terminal and look for change in DC level when shorted and when open?
If I understood what you mentioned, when I set the scope to the most sensitive setting  which is 5mV/ I see a noisy sinusoidal like wave oscillating around 0V when the probe is open.

When it is shorted with the 50 Ohm resistor I get a almost non ocillating value of 0V.
Did I do it right? And if so, that would mean that as both measurements are around 0V, there was no such current leak?
Thanks

[Satangoss]

Hello everybody,

I would like to ask you experienced guys how do I know if my Oscilloscope inputs are working properly.

Welcome to the forum.

Quickest sanity check is the probe compensation output. Period.
1 KHz @ ~3.2V.

Self Cal will pick up any deeper issues but it takes 5-10 minutes to complete.

Hello tautech, thanks for welcoming and the advice.
I just run probe calibration in all 4 ch and they all seem to be okay.
Thanks

[David Hess]

The input protection specifications apply at all vertical sensitivity settings so there should have been no damage.

The most common subtle damage is excessive leakage current which will cause a DC offset.  To check this, use the most sensitive vertical sensitivity setting and look for a change in DC level between having the input open and the input shorted.  A 50 ohm termination works fine as a short.

Hi David,

First thank you for your time and advice. Apologize for my ignorance, but to be sure how do I do that? Just place a 50 Ohm resistor shorting the probe ground terminal the probing tip terminal and look for change in DC level when shorted and when open?

I mean without a probe.  Check the offset with nothing connected to the BNC input, and then check the offset with a 50 ohm termination attached to the BNC input.  If the offset changes, then the input circuits are damaged and causing excessive leakage.