Voltage reach zero

[engcad]

Hi Every one

I'm new to labview. 

I use a high accuracy load cell and signal conditioner which provide precise excitation and output (10 V)

The problem that when I use the DAQ card (myDAQ) to measure the output voltage 

The voltage reaches zero for finite time as in the image however it is very stable at zero (at no load)

Also the same problem I found earlier when measuring a 9V DC battery

Any ideas?

[PackersFan]

Looks like a wiring problem to me.

[engcad]

All connections checked and good

aaaaaaaaaah very confused

[johnsold]

Please post a diagram showing exactly how everything is connected.  Also pst yoru VI with some typical data saved as default.

Lynn

[engcad]

Moment please

my signal conditioner is programmed via serial port

when I connect it to pc via usb-232 converter in the same time of aqcuiring data then all readings are ok and no ripples or spikes to zero 

The connection diagram and VI block are attatched

[johnsold · Accepted solution]

I suspect that you have a grounding problem. The signal conditioner is probably grounded through the USB/RS-232 connection when you have that connected. When it is not connected through the USB, it may not be grounded.

Try connecting the AGND of the MyDAQ to the 24 V DC- connection or to a ground connection on the signal conditioner.

Lynn

[engcad]

thanks very much

[engcad]

grounding the signal conditioner had solved the problem

[johnsold]

Thank you for letting us know.  When you report what solved the problem for you, it can help someone else with a similar problem.

Lynn