Adam Equipment CBW 100a, Руководство по обслуживанию

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@Adam Equipment Company 2005 14
The expected change to the output is:
Vout = (2mv/V) * Vext * Mass
capacity of load cell
For example a 2mv/V load cell of 30Kg capacity with 20Kg placed on it. Vext is 5
volts would give a output of approximately:
Vout = (2mv/V) * Vext * Mass = 2mv/V * 5V * 20Kg = 6.7mv
capacity of load cell 30kg
If the load cell has been damaged the no load voltage will likely be greater than 3mv
or the loaded voltage will be grossly different from the expected value. Remember
the loaded voltage will be offset by the amount of zero load voltage measured.
The load cell can be tested while it is connected to the A/D converter circuit board,
using the scale power supply for excitation voltage.
TESTING LOAD CELLS IN THE SCALE
The signal from the load cells is amplified by the circuits on the A/D circuit board.
The signal needs to be amplified to make it acceptable for the A/D converter used.
The TCC/CBW scales amplify the input by 200, and change the no load voltage to
about +2.5V. The TFC and TFW scales use a gain of 500.
The amplified and offset voltage is measured at pin 6 of IC7, the INA118P amplifier
IC. This voltage is sent to the filter and then to the A/D converter.
8.0 CBW RS-232 INSTALLATION
The addition of the RS-232 interface for these scales requires the following:
Scale
Lead with 9-pin d-subminiature connector
Cover with RS-232 Connector Hole cut out
A new main PCB with RS-232 interface included
The scale will have a PCB for the main parts of the electronics. These boards will not
have any parts included for the RS-232 interface. Replace the main PCB with the
new one which has the RS-232 interface included. Fit the CPU and the jumpers -
taken from the earlier PCB into the new PCB.
All parameters and Calibration including the Two Point Factory Calibration must be
set before the new PCB will be put to use for weighing.