Measurement Computing DBK Part 2 - Manual (Page 22)

DBK43A & DBK43B, pg. 2 899892 DBK Option Cards and Modules
For half-bridge and quarter-bridge strain gages, the modules can accommodate user-
supplied BCRs (bridge-completion resistors) that complete the bridge circuit. The bridge
circuit must be complete for the strain gage module to operate correctly.
Each channel of the strain gage module offers a selectable 3-pole, low-pass filter with a user-set cut-off
frequency. Remote-sense terminals are provided to make 6-wire Kelvin connections. Up to two modules
can be connected to each of 16 analog base channels for up to 256 input signals.
DBK43A and DBK43B Block Diagram
Note A: DBK43A uses Mini DIN-6 connectors for signal inputs. DBK43B uses removable screw-terminal blocks.
Note B: Channels 0 through 7 correspond with circuit board channels 100 to 800, as discussed in the Hardware
Configuration section.
Both strain gage modules provide an amplifier gain range of ×100 to ×1250 for use with strain gages having
0.4 to 10 mV/V sensitivities. Most strain gages are specified for a full-scale value of weight, force, tension,
pressure, or deflection with an output of mV/V of excitation. For example, a strain gage with a full-scale rating of
1000 lb of tension might output 2 mV/V of excitation at full load. With an excitation of 10 VDC, 1000 pounds of
load would produce an output of 20 mV.
The module’s 0 to 5 VDC offset and output-scaling permit nulling of large quiescent (inactive or motionless) loads
and expansion of the dynamic range for maximum resolution. Typically, the quiescent output is non-zero. Prior to
a force being applied, a mounted strain gage can be in a state of partial deflection resulting in an output. In the case
of a tension gage, this output may be due to the weight of a hook or empty container.
The modules include an internal excitation voltage source. The wide-range excitation regulator is adjustable from
1.5 to 10.5 VDC with a current limit of 50 mA.