How to wire 2 Pyranometers to one NI 9203 module?

[Su_Sa_Na]

Hi all,

I just started to work with LabView and NI Hardware and I have a problem with the NI 9203 analogue input module.

I want to connect two Pyranometers SMP 10 A (sensors to measure the intensity of solar radiation) to one NI 9203 module at the same time.

The output signal of the Pyranometers is 4-20 mA.

Here is the instruction sheet, where the wires of the sensor are shown:

http://www.rg-messtechnik.de/assets/files/Aktuelle-PDF/ka_smp-pyranometer.pdf

Is it possible to connect both sensors at the same time?

When I connect one sensor, it is no problem and I get a current signal, that seems correct.

Therefor I connect the black and white wire of the sensor to the negative and positive lead of a 12 VDC power supply; the green wire (analogue out) to AI 0 of NI 9203 and the brown wire (analogue ground) to the COM port of NI 9203.

But I don´t know how to connect two of these Pyranometers.

My first try to connect the other Pyranometer (with a seperate power supply) in the same way as the first one, didn´t work.

(Green wire to the second analogue input channel AI1, brown wire added to the COM port (so that there are two wires in the COM port now)).

Then the current signal of both sensors is about 0 in LabView.

Then I connected both sensors to the same power supply (12 VDC); the green wires of the sensors to AI0 and AI1 of NI 9203 and the brown wires to the COM port.

But this way doesn´t work either. Then the current signals are still about 0 in LabView.

Does anyone know how to connect two of these sensors to NI 9203?

Please help!

Susanna

[Roland_Win]

Hi,

With a NI 9203 you can only measure currents that are within the same circuit.

You would need a Channel to Channel isolated Module like the NI 9227.

You could also use a differential analog Input Module like the NI 9205 and a Shunt to measure the voltage change.  

[Su_Sa_Na]

Hey,

thank you for your answer!

I will have a look at the NI 9227.

Ciao Susanna