@Adam Equipment Company 2004
3
3.0 INTRODUCTION
The scales are all based on resistance strain gauge load cells. The load cells
output a small voltage in response to a load placed on the weighing platform.
The voltage is in the range of approximately 10mv for a full capacity load.
The signal from the load cell is amplified by an instrument amplifier with
differential inputs. This voltage is then sent to another amplifier that will filter
the response to eliminate high frequency signals (above 5 Hz.). This voltage
is then presented to an A/D converter for conversion to a digital value for use
by the microprocessor.
It may be necessary to replace a load cell if it is damaged. In this case it may
be necessary to change resistors on the PCB to force the A/D counts to be
correct. A table showing the resistor values and A/D counts follows.
The scales have the ability to view the counts from the A/D converter. Press
the
[Units]
key then turn on the scale using the
[On/Off]
key. Release the
[Units]
key to show the A/D counts.
The load cell connections are:
Before any changes are made to the scale, it will be necessary to trouble-
shoot the problems and determine the best method to solve the problems.
Refer to the Trouble-shooting Guide for suggestions.
PCB main board
Red (E+)
Black (E-)
White (S-)
Green (S+)
J3
