A
2401 Stanwell Drive Concord, California 94520 Ph: 925/687-4411 or 800/542-3355 Fax: 925/687-3333 www.calex.com Email: sales@calex.com
1
4/2001
Model 463 Bridgesensor
463 Block Diagram
Features
!
Complete Strain Gage Bridge Signal Conditioner
!
Isolated 10 Volt Output
!
Bridge Balance with 80% Tare Offset Capability
!
Excitation Supply Capable of Driving
Four Load Cells
!
AC Powered
!
Rugged Epoxy Encapsulated Design
Applications
!
Weighing with Load Cells
!
Low Frequency Strain Measurements
!
Process Control Pressure Transducers
!
Can Be Used With All Types of
Low Output Sensors
Description
The Model 463 is a self contained, AC powered signal
conditioner for bridge type instrumentation. It contains a
precision instrumentation amplifier with isolated, filtered output
and a highly regulated, low noise, adjustable output bridge
excitation source. The unit is completely encapsulated for
use in rugged environments.
A
2401 Stanwell Drive Concord, California 94520 Ph: 925/687-4411 or 800/542-3355 Fax: 925/687-3333 www.calex.com Email: sales@calex.com
2
4/2001
Model 463 Bridgesensor
Specifications
NOTE: Unless otherwise noted, specifications apply after 1 hour warm up at
25C ambient. Temperature coefficients apply between 0C and 55C ambient.
Getting Started with the Model 463
1.
Excitation Supply. If remote sensing is not used, connect
+Sense to +Excitation, terminal 3 to 4, and connect
-Sense to -Excitation, terminal 1 to 2. These connections
must be made to adjust the supply as in step 2.
2.
Apply power to the Model 463 and adjust the Excitation
supply. Turn SWB-1 "ON" for a fixed 10 Volts. This will set
the supply to 10.2 2.5% and provide the best temperature
stability. For voltages between 5 and 10 Volts, place
SWB-1 in the "OFF" position and set the Excitation
Supply with potentiometer E. SWB-2 may be in either
position.
3.
Turn the power to the Model 463 "OFF" and connect the
load cell to the Model 463 Excitation terminals and the
Amplifier Inputs.
4.
Turn on power to the 463.
5.
Turn SWA-3 "ON". (To set output ZERO)
6.
Select the expected full scale signal range according to
the table with SWA-4 and SWA-5. If the output from the
load cell is not known, set both SW-4 and SW-5 "ON" for
the 40-50mV range.
7.
Select required ZERO output range. SWA-2 "ON" for
zero Volts or SWA-2 "OFF" for +2 Volts.
8.
Adjust D potentiometer for 0 or +2 Volts.
9.
Turn SWA-3 "OFF". Expect output to change.
10. Apply no load or dead weight to load cell.
11. Adjust TARE potentiometers A and B for the same ZERO
output set in Step 8. SWA-1 "OFF" provides a bridge
output balance of -3mV to +15mV, and "ON" between
+15mV and +25mV, referred to the amplifier input. This
adjustment does not change the output of the bridge.
12. Apply full scale load and adjust SPAN (GAIN)
potentiometer C for the desired full scale output. Set
Range switches SWA-4 and SWA-5 as required.
13. Remove full scale load and check ZERO output. Adjust
FINE TARE potentiometer A if required.
14. Recheck full scale as in Step 12.
15. End.
Note:
If the amplifier is used without using the 463 Excitation
Supply, the external power supply low side must be
connected to the -EXCITATION pin 2 on the Model
463, or one of the inputs must be tied to pin 2,
-EXCITATION. This provides a DC return path for
the finite amplifier input current.
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A
2401 Stanwell Drive Concord, California 94520 Ph: 925/687-4411 or 800/542-3355 Fax: 925/687-3333 www.calex.com Email: sales@calex.com
3
4/2001
Model 463 Bridgesensor
Mechanical Specifications
SWA - Control Switch
Amplifier
The amplifier is a true differential input, low drift Instrumentation
amplifier with less than 100pA input current. It has a common
mode range of 5 Volts with respect to the - EXCITATION
supply terminal and a minimum of 90dB rejection of the
common mode voltage. The input amplifier and excitation
supply are DC isolated from the AC line and the output.
Tare Weight Compensation
The Model 463 has two different zero controls. One is called
the OUTPUT zero and can be set to 0 Volts or + 2 Volts with
SWA-2. The other zero control is called TARE. SWA-1 allows
the selection of one of two TARE ranges, -3mV to 15mV or
+15mV to +25mV. Potentiometers are available for COARSE
and FINE TARE adjustments.
Connecting to a Sensor
Any amplifier has a finite input current which must have DC
return path to the amplifier power supplies. This path is
automatically provided when the Model 463 Bridge Excitation
Supply is used to excite the sensor. If an external supply is
used, one side of the external supply must be connected to the
Model 463 -EXCITATION, Terminal 2. Be sure that the
common mode voltage limits are observed. This would
generally limit the external power supply to 10 Volts assuming
that half the voltage would be common mode, as is the case
when exciting a full bridge.
When the full scale output of a sensor is measured in millivolts,
say 10 millivolts, care must be exercised in wiring systems. At
10 millivolts full scale, each microvolt (10
-6
Volts) contributes
0.01% of full scale output. Wire connections can generate
microvolts of potential due to contact potentials. These will
also be thermoelectric potentials and thus vary with
temperature differences. All wires used in connecting up the
Model 463 should be of the same material. If any intervening
connections are made such as a terminal block, the terminal
block connecting points should have good thermal contact so
they will always be at the same temperature and thus cancel
each other.
Transducer Excitation
The bridge excitation supply voltage is set by SWB-1 and
potentiometer E. Set SWB-1 ON for a fixed 10 Volts. This will
provide the best temperature stability. The supply can be
adjusted between 5 and 10 Volts by setting SWB-1 OFF and
adjusting potentiometer E. The supply will deliver up to
120mA current at any voltage setting to power up to four 350
ohm sensors.
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