B&B Electronics FBDA User Manual

Documentation Number FBDA0797 Manual 

7 

 

 
 

The FBDA has several different gain settings to provide the 

largest possible voltage range for an A/D converter.  The gain of the 
FBDA is selected using a jumper, 6 jumper pins (labeled 1-6), and a 
potentiometer (labeled P1).  The FBDA is calibrated at the factory to 
have a gain of 80  ± 2.  To change the gain of the FBDA the 
following steps should be followed: 
 
1.   Remove the cover from the FBDA using a small slotted 

screwdriver. 

2.   There are six jumper pins labeled 1-6.  Place the jumper on the 

two pins selected from Table 3.1 below.  Placing the jumper on 
the two selected pins will set a gain near the values listed in 
Table 3.1.  

3.   Make all of the required connections (power supply, A/D 

converter, sensor, and excitation voltage), and turn on the 
power. 

4.   Set up your sensor to provide a known input signal for the 

FBDA.  If you are using a load cell, place a known weight on the 
load cell.  This will produce a known input signal. 

5.   The output voltage from the FBDA can be read from DB-25 pin 8 

(A/D 0 on B&B Electronics’ SDAXX data acquisition modules). 

6.   Adjust P1 to trim the gain to an exact value.  The gain equation 

is shown below.  ((SIG+) - (SIG-)) is the input signal. 

 

 
1.   The potentiometer (P1) becomes more critical as the gain is 

increased. 

2.   The gain range of 220 to 1000 is entirely decided by P1.  When 

P1 is turned completely in counter-clock-wise, the Gain will be 
close to 220.  When P1 is turned completely clock-wise, the 
Gain will be greater than 1000. 

 

25 

Jumper pin 5 to pin 6 

40 

Jumper pin 4 to pin 5 

80 

Jumper pin 2 to pin 3 

220-1000 

Jumper pin 1 to pin 2