Dynamic signal problem

[peco23]

Hello,

I have the SCXI-1000 chassis, with one SCXI 1120, two SCXI 1121, and the two SCXI 1321 connection terminals.
I need some help with the pressure measurement in a compressor. By the measuremenet, the transducer doesn´t show
the dynamic changes (suction and discharge), when the compressor is runnig. I try to acquire sinusoidal signal (100Hz)
from generator, but my acquisition show me only straight line, not sinusoid. Then I try to measure voltage on a battery.
When I connect the battery, the change in voltage output was immediately,
but when I disconnect the battery, the voltage is falling down very slowly (look at "voltage.jpg" image).
I measure on the second SCXI 1121 also, change the channels, change the jumper settings,
try to measure with other three pressure transducers, but the effect was the same.
I don´t know where is the problem, setting up the jumpers, wrong signal connections to terminal module, broken
measurement module.

Any help would be appreciated.

regards Peco23

[S_Hong]

Hi peco23,

The SCXI-1121 has a two-stage filter built into the device for each channel. Each filter stage is configurable to two different settings via jumpers: 4 Hz and 10 kHz. Have you verified and made sure to set the proper jumpers for both filters to 10 kHz as shown in page 2-9 of your user manual? Also, could you try generating a 1 Hz sine wave and see if you can get any measurements?

As for the slowly decreasing voltage behavior at the input, the reason for this is simply because without any source connected, the input is no longer referenced and therefore it becomes a floating voltage. With no reference, the input will usually drift to either rails of your system. This is expected behavior.

I hope this helps,

[peco23]

Hi S_Hong,

I had the jumper filter set to 4Hz. I set it to 10 kHz and now everything is working well. Thank you for your help.

Regards Peco23