How to measure current with FP-AI-110 with external power supply?

[OGL]

I wired some flow and pressure transmitters to a FP-AI-110 module. I used Vsup(+) and Iin(-) terminals as the manual says with an external 24VDC power supply. However, my instruments are only getting 5V and therefore they don't work. I wonder what do I need to change for them to work.

[Jorge M.]

Hello,

according to your explanation, I guess these are the connections you are making:

a) External Power supply (+24) -> V on the FP
b) External Power supply (GND) -> C on the FP
c) Power for the sensor -> Vsup on the FP
d) Current output of the sensor -> Iin on the FP

Is this right?

If you check the diagram on the NI 2005 Catalog (page 349, Figure2, the one at the right), that's what it is supposed to be. As you can see, there's a 100 ohm resistor in series with your device, and this has to be taken into account as it may affect your device's behavior...

How are you measuring the 5 Volts you say your sensors are getting?

According to the diagram, if you measure Voltage between Vsup and COM, you would get the Voltage applied to V and C, otherwise something's really wrong.

I hope this helps to find if there's any misconnection on your setup.

Regards,

JorgeM.

[OGL]

Thank you Jorge M,

I measured the voltages across Vsup and COM and they were 24VDC in all chanels, however, my 4 instruments were still not being powered. When I moved them to the last, unused, 4 chanels they started reading well. It looks like the first 4 chanels on that FP-AI-110 module are defective.

Oscar

[Jorge M.]

OK, then that was the issue. If you are interested in repairing the module, please contact your local NI branch for information on repair services. You'll find the contacts on the web page (i.e. www.ni.com/spain).

Regards,

Jorge M.