NI9205 used to measure voltage Kulite sensor

[polymtl]

Hi everyone,

I'm working on a project for the university. It's an axial compressor and we need to measure high frequency pressure at some places.

We are using this sensor: Kulite XT-190-25A (datasheet: http://www.kulite.com/docs/products/XT-190.pdf)

These sensors have 4 pins, two for the outputs and two for the inputs. I'm using an amplificator : Dataforth SCM5B38-07 (https://www.dataforth.com/catalog/pdf/scm5b38w.pdf)

I have a NIcDAC9178 with a card NI9205 to read the voltage of the sensor.

My problem is the following one: when I connect the sensor to the board, I'm not able to see any variation of voltage... Even if I blow on the sensor , nothing.

 Do you think it could be a problem on my board, or is it my connections?

Thank you in advance for your help!

[fromm8]

Hello Polymtl

We would like to know how you are connecting the sensor in order to know if the problem is that one. For example:

- Are you using differential or RSE mode?

- Are you able to run the self-test successfully?

- Are you able to use the test panels to measure the voltage of a battery for example?

- what pins are you using?

I would like to add that I have heard this issue before and some sensors measure "voltage variation" and in that case is expected to read 0 V if there is no variaton in the pressure.. you should check how this sensor works

Regards

Frank R.

[polymtl]

Hi fromm8,

I treid both: differential and RSE, and nothing changed.

What is the self-test? Is it ine the Measurement and Acquisition System feature?

I already measure a voltage with the board, with another sensor.

For the pin, I will check tomorrow, I don't remember....

Maybe it's a problem with the amplification of the sensor, but I'm not sure.

[fromm8]

Hello Polymtl

The self-test is a function in MAX that allows you to test if the communication with the card is fine. I still think that probably your sensor measure voltage variations

Regards

Frank R.

[AnalogKid2DigitalMan]

\Are you supplying power to the sensor?

Post a sketch of your wiring connections.

Here is a working link to the sensor:

http://www.kulite.com/docs/products/XT-190.pdf

EDITS BELOW:

 Have you enabled the ouput voltage for the strain gauge conditioning module?

http://www.dataforth.com/catalog/pdf/scm5b38w.pdf

You may just want to connect the sensor directly to the DAQ initially and set the voltage range accordingly.

-AK2DM

[polymtl]

Hello guys,

@fromm8: I tried the self test and it's working.

@AnalogKidYes I have a power Supply. The model is Acopian 5EB100 (http://www.acopian.com/store/productdetail.aspx?q=i572)

Here is a copy of my wiring connections.

AC on the supply is connected to a power bar. (60Hz, 110V)

thank you for you time and precious help!

[AnalogKid2DigitalMan]

Per your schematic, it looks like the Dataforth PCOM and +5 power connections are wired with the wrong polarity to the Acopian power supply. If this is how it is wired, it may have damaged the signal conditioner.

Also on the Dataforth in order to enable the output, Pin 19 (I/O COM) must be connected to Pin 22 (RD EN\) as I asked about previously.

Looks like the NI 9205 is wired for differential so set up your acquaition parameters accordingly.

Hope this helps.

-AK2DM

[fromm8]

Hello Polymtl

That means that your card is fine. According to your connections you are implementing a differential measurement, so you should set that option in your test panels. You could also test a battery or power supply just to assure that your 9205 is working fine... Have you tried that? 

Regards

Frank R

[polymtl]

I made a mistakes on my sketch, the connection with the supply is correct.

My dataforth device is onnected on a board SCMPB03 ( http://www.dataforth.com/catalog/pdf/scm5baccs.pdf )

I've tried to connect a 5V supply, and I'm able to read correctly the voltage.

Here are two screenshots, one in differential mode, the other one in RSE mode.

[01] Differential mode

[02] RSE mode

When i'm blowing on the sensor, there is no variation on my graphs. For all of them...

[AnalogKid2DigitalMan]

One issue I see regarless of the input configuration is you are picking up 60Hz AC power line frequencies.

This could be saturating and masking your true signal or may also incate you have a bad wiring connection. Since the amplitude is quite large, I suspect it may be coming from the input side to the Dataforth module.

The cable from the sensor is shielded, have you tried connecting this to ground?

EDIT: A picture of your entire setup may be of use.

-AK2DM