Tool/software:
Hi! I am working with INA333 to amplify a wheatstone bridge output voltage. Here is the circuit in KiCAD:
I am testing the circuit with the INA output connected to a stm32f405-microcontroller ADC pin. The output is showing always 0V, no matter what value of resistance is present in both potentiometers (gain and offset adjustment).
Any ideias on what could be happening?
Thx!
Hi Ulhoa,
The issues are that INA333's input bias and reference voltage are not configured properly, since you are using single supply rail. The instrumentation amplifier is designed to measure small differential input and amplifier the differential signal.
I made up an example with Gain = 50V/V and Vref = 1.25Vdc. You can download the Analog Engineer's calculator link below.
www.ti.com/.../ANALOG-ENGINEER-CALChttps://www.ti.com/tool/ANALOG-ENGINEER-CALC
It looks like that you are trying to sense current with INA333. For single supply rail, you wound need to establish Vcm voltage, which is configured at 1.6Vdc. Then you need to configure a Vref = 1.25V to establish a reference voltage for 0 differential signal. If the current is bidirectional, then your output will move around the Vref linearly. The input differential signal in this configuration is from -33mV to 39mV, see the image above.
If you want to use Vcm near GND, then you would need to use dual supply rails.
INA333 Current Sensing 09252024.TSC
If you have other questions, please let me know.
Best,
Raymond
