Measurement Computing WaveBook rev.3.0 - Manual (Page 62)

3-30 WBK16, WBK Expansion Options, ch03B 6-23-99 WaveBook User’s Manual
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.