strain gauge excitation

[kojay]

Hi,

I am using NI9219 for strain measurements. I am not sure what excitation voltalge should be set in DAQmx Create Channel (AI strain Gage vi).

The exmaple vi provided in LabVIEW is set at 2.5V. The 9219 manual shows a few different values (Half-bridge: 2.5 V for 700 ohms of load resistance and 2.0 V for 240 ohms, and Full-bridge: 2.7 V for 350 ohms and 2.2 V for 120 ohms). 

How can I determine the excitation values? (Or how can I know load resistance?) I use both half- and full-bridge configurations.

Thank you in advance.

[alcava.cr]

Hi there,

The load is determined by the strain gage itself, since we are completing a bridge all resistors in the configuration should have equal values in ohms...same with the task configuration.

About the excitation, it depends on the values you want to use according to the module's capabilities. I would recommend checking the next articles for a deeper understanding of the hardware & setup:

- Measuring Strain with Strain Gages
- Advantages of the NI 9237 Over the NI 9219 in Strain Measurements

I hope this can get you started