Help Pressure transmitter - Use NI9472 or NI9263??

[JParedes]

Hello guys. I am trying to figure out which voltage output module would work best with to apply a voltage to a pressure transmitter I recently purchased. I am using the following pressure transmitter (0-300 psi range, 2 wire electrical connection): http://www.dwyer-inst.com/Products/Product.cfm?Group_ID=20134&Product_ID=1577&sPageName=Specs

I own the following two voltage output modules:

NI 9263 - 4-Channel, 100 kS/s, 16-bit, ±10 V, Analog Output Module

NI 9472 - 8 Ch, 24 V Logic, 100 µs Sourcing C Series Digital Output Module

My question is which of the following output modules is the correct one to use for this pressure transmitter? I have been trying to use the 9263 but I haven't gotten it to work correctly. I noticed that the pressure transmitter spec sheet said it needed a 9-30 VDC power requirement. Does the VDC tag on the power requirement indicate that I SHOULD use the 9472 instead since it is digital?

Thanks for your help! Just in case you were curious I am attaching the VI I am currently trying to get to work.

Javier

[kekin]

It's not just about VDC when it comes to pwer requirements. You have to also look at the current sourcing requirement as well. Please make sure that the driving capability of your card matches.

[Kyle_A.]

Hi Javier,

According to the spec page, the 9 to 30 VDC is just the power requirement for the sensor to operate normally.  Notice that the output signal from this pressure sensor is a 4 to 20mA current loop.  Thus, if you wish to read the values off the sensor you will need either a current sinking input module or a shunt resistor to read the voltage from the current loop. 

Also, looking at the spec sheet it seems that the current sourcing requirement for the external power supply needs a minimum of 40mA DC to power the control loop.  The 9263 can only source 1mA so that could not be used to power the system.  The 9472 does have the current spec and the voltage spec, but it requires use of an external power supply already, so is there any reason why you wouldn't just hook that up directly to the sensor?  More information on 9472 operation can be found in the specifications manual.  I also found a good article describing power supply considerations for pressure transmitters, look at that if you have other questions.

[JParedes]

Hi Kyle,

I am using an NI 9203 current input module to read the currents from the pressure transmitters. So that elminated having to use a resistor in parallel with the pressure transmitter to convert the current readings into voltages. I ended up just using a seperate variable DC power supply (4-28 V) to power the pressure transmitters and the VI is finally working!

I decided to use the DC power supply because I didn't know how to create a constant 24 V output signal with the 9472 module in LabVIEW. Could I just hook up the power supply that hooks into the 9472 directly to the pressure transmitters? I would think that it is probably running at too high a voltage or something. I haven't looked at the power supply specs since it isn't near me at the time.

If you could point me in the right direction on how to generate a constant 24V+ output signal with the 9472 I could just use that instead of having to haul around the DC power supply that I am currently using.

Thanks for your help! I attached the current VI if you are interested in seeing the working version.

[Kyle_A.]

Hi Javier,

You would just need to output a static output high on one line and look at this equation to determine how much voltage the 9472 outputs from the manual:  Output voltage (V0) = Vsup – (I0 · R0)

Concerning the power supply that is used with the 9472, the power supply specs are as follows, reference page 10 of the specification manual for more information and warnings:

A simple example to write to a digital output channel a high value is the Write Dig Chan.vi from LabVIEW's Example Finder in the Help menu » Find Examples.

[Jon_Z]

Hola Javier,

   The NI9472 has a 24VDC power input ( terminal 8), think it can not generate 24VDC by itself. I have designed systems with 4-20 mA inputs and I use 24VDC power supplyes. I wire the +24V of the power supply to + terminal of the sensor, then the - terminal of the sensor to AIx terminal of the 4-20 mA input module and the COM of the input module to the - terminal of the power supply.

  Best regards,

Jon