A
D-303
Model 436 Bridgesensor
Manufacturing Company, Inc. Concord, California 94520 Ph: 925/687-4411 or 800/542-3355 Fax: 925/687-3333 www.calex.com Email: sales@calex.com
1
436 Block Diagram
Description
The Model 436 is a self contained, current output, DC powered
signal conditioner for bridge type instrumentation. It contains
a precision differential amplifier with filtered output and a
highly regulated, low noise, adjustable output bridge excitation
source. The Model 436 contains an isolated DC/DC converter
which operates off 10 to 36 Volts DC. The unit is completely
encapsulated for use in rugged environments.
Features
!
Complete Strain Gage Bridge Signal Conditioner
!
4-20 mA or 12 8mA Output
!
Contains Isolated DC/DC Converter
!
Use with 0.5mV/V to 10mV/V Sensors
!
Drives Four 350 ohm Bridges at 10 Volts
!
Rugged Epoxy Encapsulated Design
Applications
!
Weighing with Load Cells
!
Process Control Add-on Loops
!
Intrinsically Safe Applications
!
Can Be Used With All Types of
Low Output Sensors
A
D-303
Model 436 Bridgesensor
Manufacturing Company, Inc. Concord, California 94520 Ph: 925/687-4411 or 800/542-3355 Fax: 925/687-3333 www.calex.com Email: sales@calex.com
2
Specifications
NOTE: Specifications apply 0C to 55C and 10 to 36 Volts DC input.
Getting Started with the Model 436
This procedure is for large tare weights, i.e. greater than about
10% of the cell's full scale rating.
I.
Hook Up Procedure
A. Connect the + out of your load cell to the + INPUT,
pin 10.
B. Connect the - out of your load cell to the - INPUT,
pin 9.
Note:
If the SENSE are not used in your application, the
connections in step C & D need to be
followed. If the SENSE are going to be used, do not
jumper them as described in steps C & D.
C. Connect +Excitation, pin 6, to the + excitation of your
load cell and jumper the + SENSE, pin 5, to +Excitation,
pin 6.
D. Connect -Excitation, pin 4, to the - excitation of your
load cell and jumper the - SENSE, pin 3, to -Excitation,
pin 4.
E. Determine the voltage of the power supply to be used
and adjust within the 10 to 36 volt range if necessary
before connecting to the power pins, 1 and 2.
F. Verify that the hook up procedure is complete.
G. Turn on the power supply and check the bridge
excitation supply.
II.
Calibration Procedure
A. Set the required load cell excitation voltage by using
the B+ ADJUST.
B. Set the GAIN SWITCH to the expected load cell
output.
C. Short the signal input pins 9 and 10 together with a clip
lead. Adjust the COARSE and FINE OFFSET pots, C
and B, 4 mA output current.
D. Remove the short from step C.
E. With no load on the cell, readjust the zero output.
F. Apply the live load to the cell and adjust the GAIN, pot
D, for the desired output current.
G. Use the COARSE and FINE OFFSET pots to set the
4 mA output current.
H. Repeat steps E. to G. until the desired settings are
obtained.
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A
D-303
Model 436 Bridgesensor
Manufacturing Company, Inc. Concord, California 94520 Ph: 925/687-4411 or 800/542-3355 Fax: 925/687-3333 www.calex.com Email: sales@calex.com
3
Amplifier
The built-in amplifier is a true differential input, low noise, low
drift, instrumentation amplifier. It has a high common mode
rejection ratio (CMRR) and is provided with an output offset
that is potentiometer adjustable. The output offset pots adjust
the output zero current up to 12 mA. The instrumentation
amplifier has a gain DIP switch which changes the gain by
factors of two and a gain potentiometer for fine adjustments.
The amplifier accepts input signals of 5 mV to 100 mV. The
amplifier can withstand input voltages up to 15 Volts without
damage. The output of the amplifier is filtered to be 3 dB down
at 10 Hz using a double pole Butterworth filter to minimize the
effects of high frequency electrical and physical noise on the
system.
Bridge Excitation Supply
Transducer excitation is provided by an adjustable, well
regulated, low noise power supply. The excitation voltage is
adjustable by means of a molded-in potentiometer which
allows the output voltage to be varied from 5 to 15 Volts. It is
capable of supplying up to 150mA to drive up to five 350 ohm
load cells at 10 Volts.
FIGURE A. Typical Application
FIGURE B. Gain Range Switch
The B+ supply has remote sensing provisions for 6 wire
configurations. The sense lines minimize variations in output
voltage with changes in load current or lead resistance. It
should be noted that if the sense feature is not being used,
terminal 3 must be connected to terminal 4. Terminals 5 and
6 must be connected also. The supply output, B+, may be
connected through a 300 ohm safety barrier and the sense
lines will regulate the voltage across a 350 ohm bridge
between 5 and 8 Volts.
The supply has short circuit protection to protect it against
short term faults. The output recovers automatically from
short circuit conditions once the short is removed.
Application
Figure A show a typical application using the remote sense
lines and 4-20 mA output. When using shielded cable between
the model 436 and the transducer, connect the shield to pin 4
only. Pin 4 is connected to Pin 8 inside the 436 module. Set
the switch to the expected full scale output of the transducer
as in figure B. With the 436 connected to a bridge, short the
input, pins 9 and 10, and adjust the coarse and fine offset pots
for 4.00 mA output. Then set the gain pot for full scale
calibration. Recheck the zero current. If the zero current has
changed, reset and set full scale.
The fault mode maximum output current will range from
approximately 23 mA with 1000 ohms loop resistance to 55
mA into zero loop resistance.
Only One Switch ON
For Expected Transducer Full Scale Output
10
15
20
25
30
35
40
POWER SUPPLY VOLTAGE
0
100
200
300
400
500
600
700
800
900
1000
SUPPLY CURRENT mA
MODEL 436 POWER INPUT
B+LOAD =30mA
B+LOAD =150mA
A
D-303
Model 436 Bridgesensor
Manufacturing Company, Inc. Concord, California 94520 Ph: 925/687-4411 or 800/542-3355 Fax: 925/687-3333 www.calex.com Email: sales@calex.com
4
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Mechanical Specifications
Specifically designed for rugged field use the Model 436 is
completely encapsulated in epoxy using a vacuum potting
system to insure a complete seal against corrosive
environments. It is similarly protected against shock and
vibration and will provide years of reliable accurate operation.
FIGURE C. Case Dimensions
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