AC coupling 3 Hz and 10 Hz

Hello,

I am using Dewesoft X for experimental modal analysis.

The AC coupling of sensors (Ch. setup -> Analog in -> Setup -> Coupling) has 4 options that one can choose from in the drop-down menu: AC 0.1 Hz, AC 1 Hz, AC 3 Hz, and AC 10 Hz. Using 0.1 Hz and 1 Hz works fine, but the 3 Hz and 10 Hz options do not seem to work (see attached screenshots - sensor was excited with the same sine signal for 1 Hz and 3 Hz). Moreover, 3 Hz and 10 Hz are listed neither in the Modal Analysis Brochure (https://downloads.dewesoft.com/brochures/dewesoft-modal-test-and-analysis-brochure-en.pdf) nor in the Sirius Manual (https://downloads.dewesoft.com/manuals/dewesoft-sirius-manual-en.pdf) (see attached screenshots). Hence my question: are 3 Hz and 10 Hz actually supported? Or is this some kind of display bug? 

Dear Stefan,

thank you for reaching out to us. The AC coupling in the technical specifications is a HW coupling. In the software it is possible to select AC 3 Hz and AC 10 Hz, but this is a software filter.

When AC 10 Hz is selected in the Info box you can see that the HW filter is set to 0.1 Hz:

We are already working on the manual to reflect this information.

Kind regards.

Dear Gregor,

Thank you for the clarification and for your intent to update the information in the manual.

The question is, why we don't see anything when using a 160 Hz sine signal with the 3 or 10 Hz software filter? (see AC_3Hz.png from my original post)

Best regards,

Stefan Mutaf

Dear Stefan,

from the image I can see that Measurement is set to IEPE - do you have a IEPE sensor connected to the device? What is the LED color of the module - red or green?

Can you please use the Voltage measurement instead of the IEPE. Do you see the same results. I have tested this by using a function generator outputting a sine signal with 160 Hz and I did see the signal with DC coupling set to 3 Hz or 10 Hz.

Can you please also provide the DewesoftX version that you are using.

Kind regards.

Dear Gregor,

Thank you for your quick reply.

Yes, we used an IEPE sensor (KS903B100 Triaxial Accelerometer: https://mmf.de/en/produkt/ks903b100/).

We also tried playing a 1000 Hz sound with a laptop and measuring it with a different IEPE sensor - a microphone (which by the way is from a different manufacturer). Again, the 3 Hz and 10 Hz couplings did not work (see first 2 of the attached screenshots). We tried using different channels as well, but that did not change the situation.

In both tests with IEPE sensors, the LED light on the Dewesoft module was green, or blinking green when we were in the "Channel setup".

We then did a "Voltage" measurement. We connected the laptop’s sound card directly to the Dewesoft system (via an AUX to BNC cable) and played a sine signal while the input channel was using the “Voltage” setting. Then, 3 Hz and 10 Hz worked (see the 3rd attached screenshot). There was no LED light at the respective channel on the Dewesoft system, except for when we were in the "Channel setup" - then it was blinking green.

So it looks like the 3 Hz and 10 Hz AC coupling works for "Voltage" sensors, but not for IEPE sensors.

Best regards,

Stefan Mutaf

Dear Stefan

thank you for the images. I was not able to reproduce the behavior, using a different accelerometer. Would you please be so kind and write to us at support@dewesoft.com and we can schedule a remote session where we could look at the issue in more detail?

Kind regards.

Hi,

I'm experiencing the same issues with my Sirius 8Acc+ with IEPE sensors (both accelerometers and microphones). Seen it in many versions, right now in 2023.4.

Dear Benjamin,

yes this is an issue and we already have an open ticket for it. I will notify you when the issue is resolved.

Kind regards.