strain 1520 no readings

[usuario]

Experimental Setup:

SCXI Chassis, 1520 module, 1314 Accessory; 6062E pcmcia.

Half bridge (type II), 350 ohm, same as shunt resistors (verified by manual measurement with multimeter). Self excitation (2,5V).

I want to measure strain but can't. When I begin acquisition, an initial value is shown, say, -200. The value diminishes at a constant rate until it reaches around -970, stays constant.

Manually I have verified:

Voltage P - P+ : 2.49V

Voltage Out - P: -1.24V

Voltage Out - P`+: 1.24V

Voltage across R4: 1.24 V

Voltage across R3:  1.24 V

Resistance P+ - Vout: 350 ohm

Resistance P - Vout: 350 ohm

If I try offset null calibratin, I get Error -200380 (see attached).

So, it seems like an open circuit, but I do read manually voltage across R, what is going on?

[usuario]

I attach the .vi for additional information for diagnosis.

Calibration and offset are not checked, I will try this after I have the setup working properly.

[usuario · Accepted solution]

I am amazed about the solution I found:

After checking with the multimeter that everything is as should, I have changed configuration to full bridge in order to have access with the multimeter to every point in the bridge and assure measurements.

Everything was fine manually but still not in LV.

So, after some time, I have changed DAQmx Read .vi from Multiple Channel Waveform to Single Channel Waveform, as I was only measuring one channel.

Now everything works fine.

I am amazed, I supoused that Multiple Channel included only one channel.