Electrical – Splitting strain gauge signal before amplification

sensorsignal processing

I have a strain gauge full bridge force sensor with 3mV/V sensitivity and power it with 10 V excitation, giving up to 30 mV output. Normally the output is connected to a 3rd party device's strain gauge input (call it device "X"). That device can't plot the force during measurement, so I want to show the real time data in a different device. That is why I need to get the signal. I have 2 ideas:

Option 1:
Split the strain gauge's raw output signal, for example with a device like this. Splitted signal 1 goes to device X. Splitted signal 2 goes to my own device.

Option 2:
Get an external strain gauge amplifier, scale signal to 10 V, and split 10 V signal afterwards, as in option 1. The device X also has a +-10 V input, so no problem here.

I think option 2 is better. But I really want to understand HOW the strain gauge output is affected by splitting the signal as in option 1. I know that the splitter is pure analog, no A/D conversion is happening.
How does a splitter possibly work? Is it creating a parallel circuit? Then I assume that it would not increase the load on the strain gauge output, hence having no bad effect. But if the splitter would be somehow connected serially only, I think that the total resistance increases and I am going to measure a lower voltage in device X. Is it conceptually much different splitting a strain gauge signal in contrast to a potentiometer signal (for example from a travel sensor)? Could you please explain in detail?

Best Answer

If you just have the one strain gauge and you are alright with whatever gain your selected instrumentation amp affords you I would go with Andy aka's suggestion. There are some really nice old Burr-Brown (TI bought them a long time ago) instrumentation amps for this sort of thing that have adjustable gain via a resistor and can get you a nice large scaled single-ended voltage to measure instead of the small differential voltage. For example:


If you have more than one strain gauge, or you just want more design detail control, you could instead try something like what's suggested here: