INA125P on load cell

Projects Discussion and Showcase Science and Measurement
1

Hello,
I am using INA125P for this load cell:
http://www.hbm.com/fileadmin/mediapool/hbmdoc/technical/b1000.pdf

According to this scematic:

770×503 55.3 KB

I have only 82.4mV (amplification) on output.
Why is so little ? Can’t I reach 1V and over ?

2

Hello
check that discussion in italian forum there are some pic
http://forum.arduino.cc/index.php?topic=110686.0

3

The datasheet shows some important considerations for single supply operation. Also note that the positive supply voltage must be 1.25V above the desired reference voltage, so you'll need to use VREF2.5 or VREFBG which should improve your output voltage swing.

4

You need to adjust the gain for more swing. In your diagram, the 1K resistor equates to approximately a 60x gain. A 500 ohm resistor would give you 120x gain, a 250 ohm resistor 240x gain, ad nauseum.

5

For a load cell / strain gauge you want maximum gain, start with gain = 500
(Rg = 120) and see how it goes. Datasheet has the gain equation.

Strain gauges produce microvolt outputs, which is why a standard opamp is
hopeless and a good instrumentation opamp line the INA125 is needed to interface
them.

Note the device has an input offset temperature drift of only 0.25uV/degC,
which is insanely low. Also drift with supply voltage is 3uV/V, again ultra-low