RSE and differential mode

[Dost]

Hi
I am using a E series card with Labview 7.1. i am trying to read voltage from a voltage source.I am using a conditioning box that is connected to a BNC 2090 and from here it is feed in to NI card in PC.i checked the volts via volt meter. it gives me 0.97 volt now when i try to acquire this voltage using labview i have two options either i can select differential mode or SRE mode with SRE mode it gives me 0.97 but with differential mode it keep on increasing until it reached to 4.9 the maximum range of voltage.I cannot understand this can any body please help me in understanding it.

[AnalogKid2DigitalMan]

Have you read the DAQ card manual section about NRSE, RSE and differential modes of operation? Differential may require the use of resistor from AIN- to AGND.

[Mcdan]

Dost,

I believe the BNC 2090 has switches to configure each channel. It is important that the mode you select on the BNC 2090 matches the terminal configuration you have programmed in LabVIEW.

Hope this helps,
Dan

[Dost]

thanks for reply.yes i matched the switch on bnc 2090 with that of labview .but question that i want to ask is that why it gives me two different reading on RSE and differential mode.secondly if i am using the bnc 2090 in differential mode than it is written in manual that should i read the voltage at two channel of bnc 2090 or i can read it just by pluggin in any of the channel.

[Dost]

thanks for reply.yes i matched the switch on bnc 2090 with that of labview .but question that i want to ask is that why it gives me two different reading on RSE and differential mode.secondly if i am using the bnc 2090 in differential mode than it is written in manual that should i read the voltage at two channel of bnc 2090 or i can read it just by pluggin in any of the channel.

[SimonS]

The difference in voltage between the 2 input modes should not occur if everything is correctly connected. When an input floats up to the maximum level, this often indicates there is an open circuit.

To check your setup, I suggest you initially try using a MAX test panel to measure channels under differential mode.You need to refer to the manual of the 2090 on how to connect up for using differential mode. The setup requires switches S1 to S8 be set to diff mode and then a connection made to only the first 8 BNC connectors.The inner and outer parts of the BNC, form the 2 input connections to the DAQ card.

SimonS

[Dost]

thanks.i checked my bnc it is configured in differential mode and i configured labview in differential mode too now i tested my input voltage using max test giving just range of input voltage. the voltage coming is 0.97 and it is also shown by voltmeter but at MAX test it shows me 4.9 when i configured it in differential mode but it gives me 0.97 when i configured it in RSE mode any comments on it.