B&B Electronics Strain Gauge/Load Cell Bridge Amplifier FBDA User Manual

8 

Documentation Number FBDA0797 Manual 

 

 
Sensors that incorporate bridge circuitry usually have 

noticeable zero offsets.  This should be considered when taking 
measurements and determining gain.  The easiest way to solve this 
problem is to calibrate the system while avoiding zero inputs, and 
correct for the zero offset in software. 
 
Example: 
 

If a 10lb. load cell needs to be calibrated, the suggested method 

is the following: 
 
1.   Make all of the required connections. 
2.   Place a 1lb. mass on the load cell.  Record the voltage on DB-

25 pin 8 as Vouta.  Pin 8 is A/D 0 on the SDAXX modules. 

3.   Add a second 1lb. mass onto the load cell.  Record the voltage 

on DB-25 pin 8 as Voutb. 

4.   Subtract Vouta form Voutb.  The difference is the voltage, Vout, 

which corresponds to 1lb. 

5.   Calculate what ((SIG+) - (SIG-)) is for 1lb.  This is the voltage 

produced by the sensor. 

6.   Use the Gain Equation to calculate the exact gain of the 

amplifier. 

7.   Adjust P1, and repeat process until the desired gain is achieved. 
8.   Subtract Vouta from Vout.  The difference is the zero offset 

error.  The zero offset error should be included in any equation 
conversion equation used in your software.

 

GAIN = Vout / ((SIG+) - (SIG-))