Help with pressure transducer connected to NI USB-6000

[ppaulade]

I have a pressure sensor that outputs 0-5v corresponding to 0 - 400 barS (sealed gauge).

I connected the sensor as shown in the attached photos and the pressure in that pipe is at 5 bar as shown on the gauge.

I took data at 1HZ and I should be getting a pressure reading of 5 bar after scaling. but I have attached a screenshot of the values I obtain during the test. it is at 0bar and just spikes up to >5 bar. It spikes a lot.

When the pressure in the pipe was at 0 bar, it still displayed the same type of output.

Please help.

I have attached the connection with the DAQ as well.

Pressure sensor part number: 3100-R-0400S-01-B-0-00. use this to check the data sheet. file 7 is a screenshot of the connection diagram from datasheet. code b voltage mode.

[santo_13]

The average does come to around 5bar,

May be it is high frequency oscillation that doesn't show up in analog gage?

How about the soldered wires? are they correct?

[ppaulade]

Let us assume the average is 5 bar, when there was no pressure in the pipe the graph also had spikes. the amount of spiked increased with the sample rate.

what do you mean by high frequency oscillation?

Yes the connection is correct. it was worse before i soldered. i was getting a wave form graph. i doubt i am meant to get that.

[santo_13 · Accepted solution]

Now, I see the mistake, you need to connect the GND to the DAQ' AI GND as well, not just the signal to DAQ.

[ppaulade]

So I have a bench power supply. the black clip is ground and the red is the power supplying 20V. 
So the ground of the pressure sensor is connected to the bench power supply.
Do i still need to connect the ground to the DAQ as well as the pressure sensor?

Thanks

[santo_13]

---

@ppaulade wrote:

Do i still need to connect the ground to the DAQ as well as the pressure sensor?

---

Yes, DAQ needs to know what to use as a reference to measure the signal.

[ppaulade]

Okay thank you. 

I will try that tomorrow. I will let you know if it works.

That must also be the reason why my accelerometer also gave me unrealistic values as well. 

I am guessing I can just connect the ground of the sensors to the AI ground channel of the DAQ device and not the bench power supply.

Thanks

[santo_13]

---

@ppaulade wrote:

I am guessing I can just connect the ground of the sensors to the AI ground channel of the DAQ device and not the bench power supply.

---

Yes, the key is connecting the sensor's ground to the AI GND of DAQ, which typically, in the case of non-isolated sensors, would be the sensor power supply's ground.

[ppaulade]

This is my accelerometer schematic diagram. There is no ground. The values I get are very small compared to the values I should get. The no acceleration voltage is 2.5V and sensitivity is 0.333v/g. My Z axis should read out around 2.833V but its out put is in mV and after conversion the vibration is more than 50x the actual value. 

What could be the problem? 

[ppaulade]

Problem solved.

Just needed to connect -ve exc to ground as well