B&B Electronics FBDA manual Gain = Vout / SIG+ SIG, Example

Gain Equation

GAIN = Vout / ((SIG+) - (SIG-))

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.

8Documentation Number FBDA0797 Manual

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