Measurement Computing StrainBook/616 - Manual (Page 74)

Three-Wire Quarter-Bridge Configurations
The three-wire quarter-bridge has only one strain-variable element and requires three bridge completion resistors
(BCRs). The internal half-bridge may be any two matched values, but the remaining resistor must match the
external quarter-bridge value precisely. Three of these values may be installed simultaneously when connected
as shown below; the connector pins determine which resistor is used. With all three values installed, WBK16
can accommodate all three quarter-bridge values without changing the internal resistors.
Three-Wire Quarter-Bridge (+),
Using RA (120-Ohm nominal), B Shunt Resistor
IA
Internal Bridge Completion
RA RB RC RD RE RF RG
RH
1
2
3
-Sense
+Sense
+Excitation
-Excitation
JN01
Switches
accessed
through
software
External
Bridge DB-9
Input
1
8
9
7
5
4
3
6
2 A 120-ohm resistor and its corresponding
shunt value may be installed as shown.
Three-Wire Quarter-Bridge (+),
Using RC (350-Ohm nominal), D Shunt Resistor
IA
Internal Bridge Completion
RA RB RC RD RE RF RG
RH
1
2
3
-Sense
+Sense
+Excitation
-Excitation
JN01
Switches
accessed
through
software
External
Bridge DB-9
Input
1
8
9
7
5
4
3
6
2 A 350-ohm resistor and its corresponding
shunt value may be installed as shown.
Three-Wire Quarter-Bridge (+),
Using RE (1-KOhm nominal), F Shunt Resistor
IA
Internal Bridge Completion
RA RB RC RD RE RF RG
RH
1
2
3
-Sense
+Sense
+Excitation
-Excitation
JN01
Switches
accessed
through
software
External
Bridge DB-9
Input
1
8
9
7
5
4
3
6
2 A 1000-ohm (or other value) resistor and
its corresponding shunt value may be
installed as shown.
6-10 Bridge Configurations 929494 StrainBook/616 User’s Manual