Load Cell Signal Conditioner
Calex Mfg. Co., Inc. of Concord California announces the models 433 and 463
load cell signal conditioners. The 433 and 463 are designed to work with up
to four 350 Ohm load cells to effectively handle most hopper or tank weighing
applications. Both units contain a precision instrumentation amplifier with
an isolated , filtered output and a highly regulated adjustable bridge excitation
source. The 463 and 433 are fully encapsulated for use in a variety of environments.
The input range for the 433 and 463 is 5mV to 50mV full scale. The typical
rated output of a load cell is 2mV/V or 3mV/V. With 10 Volts excitation outputs
can reach 20-30mV if the full capacity of the load cell is used. In most cases,
however, the load is derated by up to 50% resulting in outputs of 10-15mV
full scale. In some cases the weight on the cell may be a small percentage
of the capacity of the cell resulting in a very small output. This may result
in live load signals up to only 5mV or less. With a maximum gain of 2000 the
433 and 463 work effectively in virtually all applications.
The 433/463 amplifier is a high quality differential amplifier with Common
Mode Rejection of 100dB minimum. The 433 output is 4-20mA and the 463 provides
a 0-10V output. The linearity of the amplifier is ±0.01% of full scale
and the temperature stability is 0.005%/°C. Both units have a built-in
tare offset function that allows the user to tare off up to 80% full scale
of a 3mV/V load cell making the units ideal for large tare weight applications.
Calibration is a snap with the 433 and 463 due to a special feature which
eliminates interaction between zero and span. Both units incorporate a two
pole filter to eliminate unwanted high frequency noise. The cutoff frequency
is 10 Hz creating a response time of 35ms for a 10% to 90% step function change
and 100ms to arrive within 0.1% of the final value.
The built-in excitation supply provides up to 120mA making the 433 or 463
easily capable of driving four 350 Ohm load cells. The excitation voltage
is adjustable from 5 to 10 Volts. The temperature coefficient of the excitation
supply is 60 ppm. Line and load regulation is 0.02% maximum. The output noise
is only 1 mV RMS max. For maximum stability, the excitation voltage can be
fixed at 10V with the flick of an on-board DIP switch. Sense lines are included
to compensate for IR drops in long lead applications.
Both the 433 and 463 are AC powered. The units are isolated input to output
and from power. Ambient operating range is -25°C to +55°C. The form
factor of the 433/463 is 3.75" x 2.0" x 2.87"H. The case incorporates
through holes and mounting hardware for backplane mounting or the user can
choose the optional DIN mounting adapter. All connections are made to readily
accessible screw terminals located on top of each unit. The 433 and 463 are
backed by Calex’s five year warranty.
Complete Datasheet: