Check Oscilloscope input integrity - Siglent 1104X-E - Page 1
Forum section: electronics / beginners

author: Satangoss
author_rank: Newbie
timestamp: February 08, 2022, 04:32:46 am
content: 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.

author: bdunham7
author_rank: Super Contributor
timestamp: February 08, 2022, 04:53:12 am
content: 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.

author: David Hess
author_rank: Super Contributor
timestamp: February 08, 2022, 04:57:40 pm
content: 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.

author: tautech
author_rank: Super Contributor
timestamp: February 09, 2022, 09:23:22 pm
content: Quote from: Satangoss on February 08, 2022, 04:32:46 amWelcome 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.

author: Satangoss
author_rank: Newbie
timestamp: February 10, 2022, 01:34:31 am
content: 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).

author: Satangoss
author_rank: Newbie
timestamp: February 10, 2022, 02:02:08 am
content: Quote from: David Hess on February 08, 2022, 04:57:40 pmHi 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

author: Satangoss
author_rank: Newbie
timestamp: February 10, 2022, 03:02:02 am
content: Quote from: tautech on February 09, 2022, 09:23:22 pmHello tautech, thanks for welcoming and the advice.I just run probe calibration in all 4 ch and they all seem to be okay.Thanks

author: David Hess
author_rank: Super Contributor
timestamp: February 10, 2022, 11:41:29 pm
content: Quote from: Satangoss on February 10, 2022, 02:02:08 amI 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.