Hi everyone.
I encounter difficulties getting analog input signal (4-20 mA) using NI 9208 mounted on cDAQ 9188.
Here is the configuration :
- pressure transmitter 2-wire connected (IN: +24V) (OUT: NI 9208 AI6 pin) (power supply from external source sharing 0V and ground with NI 9208 COM pin)
- NI 9208 : Vsup = +24V (pin 19 & 37) ; COM = 0V = GND (pin 9 ; 10 ; 28 ; 29) ; AI6 = OUT pin of transmitter
[Attached, a drawing of the cabling]
- Driver NI DAQmx 9.3
- Labview 10
- Windows 7
Using a DAQ assistant configured to acquire analog current signal, the value I get on screen is fluctuating between 0.001 and 0.1 mA.
I inserted a current measuring device in line between the OUT pin of the transmitter and the AI6 pin of the 9208, here I actually get the 4-20 mA signal.
As complementary information, I measure 28V between Vsup and COM ; 0.3V between AI6 and COM ; and 27.7V between Vsup and AI6.
To make the topic as clear as possible I might add that firstly, each input channel was connected to a transmitter, each giving at screen the same value of ~0.01 mA (amperemeter not tested yet on each AI => next step of my investigation, actually performed). Then I tried to identify the problem connecting only one transmitter (AI6). Result is still the same.
As the NI 9208 once functionned well some month ago, I expect the problem to come from one transmitter which may have been wrongly connected. (I'm actually cheking all connections).
My question would be : Is the 9208 behaving typically such a damaged device (ADC?) ? Or maybe this appears like there is something I missunderstand ?
Any piece of advice would be greatly welcome.
By the way, please forgive my aproximous english.
Thanks for your consideration.
Adrien QUEUCHE
