Bridge Mode
Supported sensors
Quarter/half/full bridge; strain gauge based sensors: load cells, force transducers, torque
transducers and pressure transducers
Quarter
-
bridge completion
3 wire support; the 3rd wire keeps the measurement wire current free, eliminating wire
resistance errors in the measurement wire
Built
-
in quarter
-
bridge completion resistor
350 Ω, 0.11%, 0.6 ppm/
o
C (1.1 ppm/
o
F), wired to separate connector pin
Built
-
in half
-
bridge completion resistors
2 times 100 kΩ, 0.1%, 2 ppm/
o
C (3.6 ppm/
o
F) tracking
Bridge completion card
Access/Replacement
Access in front panel of bridge card, removable without opening mainframe
Shunt resistor
1 user mountable shunt resistor
Half
-
bridge completion resistor
2 user mountable half
-
bridge completion resistors
When used, the built
-
in half
-
bridge completion resistors are bypassed
Quarter
-
bridge completion resistor
1 user mountable quarter
-
bridge completion resistor
Wired to separate connector pin
Bridge excitation modes
User selectable Off, constant voltage or constant current
Constant voltage excitation
Selectable excitation voltage
Bipolar
±
1.0 V to
±
7.5 V DC, selectable in 0.02 V steps, maximum 85 mA
Excitation voltage accuracy
0.5% of Full Scale
Excitation voltage sense
User selectable On/Off
2 separate connector pins available; wiring requires no internal bypass
Constant current excitation
Excitation current
2.0 mA to 40.0 mA, selectable in 0.05 mA steps, using
±
7.5 V DC
Excitation current accuracy
0.5% of Full Scale
Bridge balance
Operation principal
Voltage is added to bridge to electrically balance the bridge. The remaining offset is
corrected by software auto zero
Maximum bridge balance voltage
±
250 mV
Bridge balance gain error
0.5% of Full Scale
Bridge balance restore
Reloadable bridge balance after power down
Auto zero and balance
Simultaneous execution of auto zero and balance on all channels on multiple cards,
reducing zero and balance time significantly
Bridge shunt
Bridge shunt resistor selection
4 software selectable sources
2 built
-
in shunt resistors, bridge completion card, external shunt
Bridge shunt method
Software selectable to positive or negative excitation voltage
Separate pins available to wire both selections
External shunt
2 separate connector pins to wire shunt out to sensor connection points
Built
-
in shunt resistors
Type
Metal foil
First shunt resistor
20 kΩ, 0.11%, 0.6 ppm/
o
C (1.1 ppm/
o
F)
Second shunt resistor
100 kΩ, 0.11%, 0.6 ppm/
o
C (1.1 ppm/
o
F)
Driven guard
The measured common mode voltage on positive and negative input is active driven by a
low ohmic output to the driven guard pin. Connecting the driven guard to the cable shield
minimizes the potential difference between the shield and signal wires. A lower potential
difference lowers the effect between the shield and signal wires called partial discharge.
Partial discharges result in noise on the measured signal.
+
-
Driven guard
Signal (+)
Signal (-)
+
-
Signal ground
Sensor signal
Figure A.38:
Driven guard
GEN3i
I3763-3.1 en HBM: public
421
