PASCO Load Cell and NI DAQ Interfacing

[BabyH]

Hi Jignesh,

I finally was able to get it connected to a scope and the scope says it has low resolution but detects some of the signals. THe frequencies are recorded to be ranging from 1 - 25 KHz.

Please do let me know what you think.

Thank you.

[JVP]

Hi BabyH,

What I wanted to know is what is the power source for the excitation? Are you using a power supply or a battery? Sometimes power supplies can produce noise to your output.

Regards,

Jignesh

[BabyH]

Hi Jignesh,

Sorry about that. I am using a power supply to supply the excitation voltage. As for the scope, I am getting a very random signals again. They seem periodic and they also change when the connector is pushed around.And they do not shift up or down as the sensor is subjected to varying loads.

Regards.

[Process_Systems]

You could try connecting the Com terminal of the 9215 Daq to the Neg of the Power supply unit. This completes the reference cicuit for the measurement. Note that the voltage supply for the load cell must be SUPER STABLE and NOISE FREE, as any garbage on the power supply will modulate the input to the 9215. That is the prime reason for using signal conditioning/level translation; the get the signal level up to where the ambient noise is insignificant.

After reading up on the Pasco signal conditioner, I can see why you may consider it overkill. You could also use one of the 5B signal conditioner series; I believe the 5b37. They can be bought from NI, and are reasonable priced. They have the aditional advantage of total I/O isolation, and a built-in super stable load cell power supply. The load cell/5b are then powered from a single power supply, which is internally isolated in the 5b. I have used variations on this many, many times over the years, and I very highly recommend this route.

Good luck.

Dave