Dear all,
For my project, I have to measure a difference of pressure of gas. As the range will be quite important, we will use 4 transducer, and change with a physical valve ( 1 transducer is enough for 1 test).
The material I have : - transducer (10V supply, give a signal back of 0-100mV depending on the pressure)
- data acquisition card NI PCI-6023E
- Block connectors CB 68 LPR mounted in in-house made box.
This box also contain the power supply - a transfo from 220V AC to 10V DC. The box contain also the female connection for the transducer, with old 5 pin DIN connector (http://en.wikipedia.org/wiki/DIN_connector) and the wires to the CB68LPR. To each connector, I have the possibility to put a multimeter in parallel.
Wiring connection : all female DIN power supply are in parallel, the voltage stay roughly good when connecting 2 transducer. Each AI and corresponding ground wires are twisted together until the CB 68 LPR, and all ground goes to separate AI GND. Previous version of the box, I had 100mV ground put together to the port 64 (AI GND), but I had the same problem.
I already wrote a VI which capture the data without too much problem ( I have to do an average as the signal seems to have 50Hz noise- RSE mode) as far as I connect 1 transducer to the box, no matter which analogue input canal. Also, having 2 transducer, but the cable NOT connected to the computer works fine.
The problem appears as soon as I connect 2 transducer AND the cable to the computer. In this case, I have stupid signal, often more than 100mV on the multimeter, I do not dare to let it enough time to check what LabView see.
If somebody has any idea what happen, and how to solve it, I would really appreciate.
If any more information could help understanding the problem, please ask! It can be something easy, as I am far away of my background.
Already thank you for reading all this.
Regards
Renisaac
