Balance calibration using LabVIEW

[KumarR]

Hi Friends,

I am calibrating a four component micro balance using LabVIEW 8.6 with following hardware:

USB-connected NI SCXI 1000 Chassis,

SCXI 1600 and SCXI 1520 modules.

NI SCXI 1314 as an add-on (which houses the pins for analog connections).

I am using DAQmx Vis to program. I am acquiring strain (using AI Strain Gage Vi) from each load cell of the balance. Used 5V as excitation voltage and each load cell is effectively a full bridge.

I find each channel very sensitive and am able to get voltage signal for even 5 mg of wt. Although I get signal as small as -0.00003 mV.

To find the calibration coefficients I am plotting the Load (3 mg – 7 g) Vs Voltage (of the order of 0.00003 mV – 0.07 mV).

I just wonder whether I am on right track.

Also what is the difference between acquiring signal in terms of Voltage and Strain as I am doing now?

Since I am using strain signal (I understand I am stilling getting voltage), How is it different from voltage signal?

Do I need to do anything to the strain signal before plotting against load in order to get calibration coefficients?

I would greatly appreciate if you clear my doubts. Please suggest me if my program is missing some thing important.

Thanks

[The_Red_Barron · Accepted solution]

Howdy Kumar,

You are correct that you are actually measuring a voltage to get a strain measurement.  Performing a strain acquisition (rather than a voltage acquisition) allows you to specify factor related to strain measurements such as bridge configuration, excitation voltage, etc... A Voltage task does not take these factors into account.

It looks to me like you are on the right track with your application.  From my understanding of you set up you shouldn't need to do anything else to get your coefficients.

Best Regards,

[KumarR]

Barron,

I greatly appreciate. My doubts cleared to a great extent.

Thanks

KumarR