4 wire vs wheatstone bridge with NI9205

[ravekanth]

This may be a very basic question, which I do not seem to find a concrete answer to(r maybe I do not grasp it all that well)
Hopefully I have better luck asking it directly.

I have to do strain measurements using strain gauges and I have an NI9205 AI module. I do understand how a wheatstone bridge works, but is it really necessary over say using a 4 -wire measurement system where I do nto use any other resistances?

As an added question, what would I need to go for when measuring any resistance when I have something like the NI9205 module?

wheatstone bridge or 4-wire measurements.

Hope this dilemna is clear enough( and this is the right place to post this)

[Duffy2007]

Hello ravekanth

the 9205 only can measure voltages and has no excitation, for a strain measurement you need an excitation for the strain. In the picture below you can see that two wire are used to power the strain and the other two wire delievery the values back from the strain. You could use an external power supply for the excitation, but this can influence the measurement if the output is not stable. There are also some feature like nulling and shunt calibration missed, when using the 9205.

A better option is the 9237 which has included the excitation and features.

The same, if you want to measure resistances you need an excitation with a known current, then you can measure the voltage drop on the resistor and calculate the resistor value.

Hope it helps.

[shro728]

Hello Duffy Sir,

So the NI9205 can be used along with a s type load cell right?

The only criteria is that the voltage should be constant?

I don't know why my DC power supply is fluctuating on connecting with NI9205 and the load cell.

The NIDAQ chooses configuration as Differential on connecting the green and white wires of the load cell to AI+ and AI-. Is RSE appropriate?

Sincerely,

Shreeya