daquser

Can DT9837A or DT9837B devices be used to acquire signal from a capacitive sensor/probe? The output of the capacitive sensor/probe is ± 10 volt analog via a BNC connector.

Hi @Fausto (1) We verified that the current issue with DT9857E is NOT caused by BNC cable, surroundings, or external signal connection. (2) We checked the 8 channels individually (each time only the capturing channel is selected as you emphasized) and we found that 5 out of 8 channels have the same problem as described in my previous post. The impacted channels are ch0, ch1, ch4, ch5, ch6. And ch2, ch3, ch7 are still able to capture signal correctly.

@Fausto Let me reply to your questions, I am from the same team of the engineer who started this post. (1) Sorry for the confusion, the model of the device in question is DT9857E (s/n: 1EC8B17) which we purchased not long time ago. We use the same version of DT OMNI as you suggested. Please see below the screen capture from "open layers control panel". (2) As you suggested, we used the QuickDAQ to acquire a sine signal from a function generator (1000Hz, Vpp =0.6V). Below is what we got from the DT9857E (sampling frequency 20kHz). We see the acquired signal (red line) is not uniform, and is embedded in an unknown low frequency irregular signal. (3) As a comparison, we used a DT9837A we have to acquire the same signal using the same method (same sampling frequency), and the acquired signal (blue line) is what we expect to see. I did a sample FFT comparison, it shows the FFT of DT9857E in question shows many peaks which are not from the source signal. I was wondering if you have seen similar issue with DT9857E before and what can be done to fix it? Thanks.

Is it possible to delay the starting time of external TTL trigger a little bit, so that some transient data a little before the rising or falling edge of the TTL can also be acquired? If yes, could you provide sample code in Matlab?

According to the user's manual of DT9837 series, user can set up threshold trigger on analog input channel 0, and can also program the threshold trigger value from 0.2 V to 9.8 V. Is there sample code snippet on how to set up and modify the threshold trigger value in Matlab?