Omega Engineering OMB-DBK-34A, User Manual

Page: 173 / 250

3-Wire, Quarter-Bridge, Positive (
∆
R
↓⇒ ∆
E
OUT
↑
) for DBK16
The quarter-bridge configuration makes use of one element of the strain gage. The three-wire, quarter-bridge can be
configured as “positive” or “negative.” The above figure represents the positive (plus) configuration. In this setup, the
magnitude of voltage out is inversely proportional to the change in resistance
(
∆
R
↓⇒ ∆
E
OUT
↑
). When using a quarter-
bridge external strain gage in the “positive” configuration, the following applies:
Upper Channel – R12 and R13 are to be installed.
Lower Channel – R24 and R25 are to be installed.
An external BCR is to be placed in the +EXC to R1 line (see previous figure).
Excitation
To supply excitation voltage to a single DBK16:
Connect J1 (terminals SRC+ and SRC-) to a source of filtered (not necessarily regulated) DC between
12 and 15 V.
To supply excitation to multiple DBK16s:
1. Connect J1 (terminals SRC+ and SRC-)
to a source of filtered (not necessarily
regulated) DC between 12 and 15 V.
2. Connect J2 of the powered DBK16 to J1
of the next DBK16 (see figure). The
excitation power terminals are wired in
parallel to
daisy-chain multiple DBK16s
(in systems with more than 2
transducers).
The user-supplied excitation source is attached to a voltage regulator in the DBK16 circuitry. This
regulator provides the excitation to the actual transducer (there is a separate regulator for each transducer,
hence two regulators per DBK16). Each regulator has a maximum current of 50 mA. The maximum
amount of excitation that can be provided by the DBK16 excitation regulator is represented by the
following equation:
V
EXC[MAX]
= 0.05 × R
GAGE
Where R
GAGE
= the resistance of 1 element in the bridge circuit.
DBK Option Cards and Module
879895
DBK16, pg. 5