Measurement Computing StrainBook/616 - Manual (Page 75)

StrainBook/616 User’s Manual 929494 Bridge Configurations 6-11
High-Gain Amplifier Configurations
StrainBook is useful as a programmable high-gain amplifier. No external bridge is used in these cases.
The inputs are fully differential.
Note: The differential inputs are not isolated inputs. Common mode voltage should not exceed ±10 V.
Universal High-Gain Amplifier Input, Differential
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 No pull-down resistors are required if the
input signal ground is connected to Pin 1
as shown.
Universal High-Gain Amplifier Input, Differential with Pull Downs
IA
Internal Bridge Completion
RA RB RC RD RE RF RG
R
H
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 floating input without a ground
reference, such as a battery, requires a
path for input bias currents. Pull-down
resistors of 1k to 10MΩ may be installed
as shown to provide this function.
A 10MΩ resistor would be suitable in
most cases.
These resistors are not compatible with
other bridge configurations.
Universal High-Gain Amplifier Input, Single-Ended
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 If the (-) input is ground referenced, the
input is non-differential and pull-down
resistors are not required. A floating
source would still result in a truly
differential input.