How to connect a P8AP absolute pressure sensor to the pins of a SCB-68A module?

[DimiP]

I am a new user of the SCB-68A module and I am interested in connecting a P8AP absolute pressure sensor (manufactured by HBM) to SCB. This kind of sensor has the following cables:

+ sense lead

- sense lead

+ excitation votage

- excitation voltage

+ output voltage

- output voltage

cable shield.

The input range is 0.5-5 V.

I am confused how to connect the different cables to my power supply and the SCB device.

Thank you a lot in advance!

[Dennis_Knutson]

The SCB-68 is just a dumb terminal block. You will need an actual DAQ device and use its manual to determine where to connect the signals from the sensor.

[DimiP]

Dear Dennis_Knutson,

thank you for the feedback. Actually, it is the only available module I have, so is it possible to make all my connections in this one?

Thank you

[Stephan_D]

According to Dennis_Knutson, we need to know, which Data Acquisition card do you use.

The terminal block is only an interface to connect the sensor to this card. It depends on the Data Acquisition card, how you have to connect your sensor to the connection block.

[DimiP]

I think NI PXIe-6363, X series, if I am correct.

[Stephan_D]

For this device, you can find the pinout in this KnowledgeBase:

SCB-68 Quick Reference Labels for X Series - National Instruments
http://digital.ni.com/public.nsf/allkb/E7717A2280208AEB86257869006D78A7?OpenDocument

+ sense lead -> unknown

- sense lead -> unknown

+ excitation votage -> power supply

- excitation voltage-> power supply

+ output voltage -> AI 0

- output voltage -> AI8

cable shield -> AI GND

[DimiP]

Thank you very much for the feedback. I connected the following cables with the SCB.

+ output voltage -> AI 0, - output voltage -> AI8, cable shield -> AI GND.

Concerning the two cables that go to the power supply, is it possible to connect it to the (digital) slots 8+9 of the SCB with the 5V?

Concerning the sense lead cables, you mean that they should be connected nowhere?

[Stephan_D]

I think you can use Pin 8 and 9 to supply your sensor. But be carfully, I don't know if the output voltage of 5 V is to high/low for your sensor.

It would be helpful, if you post the data sheet of the sensor into this thread.

[DimiP]

Here is the datasheet of the transducer:

http://www.hbm.com/fileadmin/mediapool/hbmdoc/technical/a2079.pdf

I use the first on the left, with the 10 mbar measuring span

[Stephan_D]

It is not as easy as I thought.

Your device use a bridge for the pressure measurement. The voltage, which you measure receive from the sensor (between output voltage+ and output voltage+) depends on the execution voltage.

Example:

You use a 2V power supply -> You receive 100mV as output voltage for pressure X

               4V  "     "            ->                   200mV  for the same pressure X

               5V  "     "            ->                   250mV  for the same pressure X

The data sheed specifies the "Nominal (rated) sensitivity" with "2±2% mV/V". Like you see, it is not mV, its mV/V, because it depends on the supply voltage. The easiest way to use such a sensor is to use the appropriated hardware

Choosing a Wheatstone Bridge Measurement Device - National Instruments
http://www.ni.com/white-paper/14341/en/

If you need accurate measurement, you also have to measure the supply voltage. If you know the supply voltage, you can devide the output voltage of the sensor through the supply voltage and your measurment result will be not influenced by the supply voltage.

If you don't measure the supply voltage, the accuracy will decrease, because you don't know the exact value of the supply.

If you use the 6361, you can't connect the sense lead cables.