B&B Electronics Strain Gauge/Load Cell Bridge Amplifier FBDA - Manual (Page 10)

Documentation Number FBDA0797 Manual 9
B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350
PH (815) 433-5100 -- FAX (815) 433-5105
Chapter 4: Excitation Voltage
Sensors that are based on a Wheatstone bridge need an
excitation voltage to excite the bridge. The FBDA provides an
adjustable excitation voltage. This excitation voltage is available on
the terminal block labeled EXV. The excitation voltage is set to
5VDC ± 0.05VDC at the factory. This voltage is referenced with
respect to GND. To adjust the excitation voltage, the following steps
should be followed:
1. Remove the cover from the FBDA module using a small slotted
screwdriver.
2. Make all of the required connections except the sensor
connections and turn on the power.
3. Using a voltmeter, measure the voltage on the terminal block
labeled EXV with respect to the GND terminal block. Adjust P2
to change the excitation voltage. The terminal block labeled A/D
1 can be used to measure the excitation voltage.
Sensors that are comprised of Wheatstone bridges usually state
the amount of output per volt of excitation voltage. An example is:
10mV output / 1V of excitation. If a 5V excitation voltage is used,
The full scale output of the sensor will be 50mV. The gain of the
FBDA should then be chosen, so that Vout does not exceed 5V (the
maximum voltage that the SDAXX line of data acquisition modules
can measure).
If for some reason the excitation voltage source in the FBDA
does not meet your needs, you can use an external excitation
voltage. If this is the case, then nothing should be connected to the
EXV terminal block, and the GND lead of the external excitation
voltage source should be connected to the GND terminal block on
the FBDA module.