Service manual Description of the electronics
05.08.03 /Jensen / Rei 34-34-00-645 b
4
Time base
From the quartz’s 4.19MHz a time base is derived which controls all timed processes in the scale.
These are, for instance, various timeouts and the on-time.
After expiry of the on-time, the supply voltage for the analog part, for voltage measurement and for the
EEPROM is switched off. The LCD is switched off, all ports are set to zero-signal level and the quartz
is stopped.
Recalibration
In order to compensate for linear measuring errors of the scale, which can, for instance, occur as a
result of the different forces of gravity at different geographical points, the module has a recalibration
function. To initiate the function, another button must be pressed when the scale is started. The
calibration counter is now displayed which is incremented whenever the scale is recalibrated. It
enables the user to check whether the scale was manipulated. If, within five seconds, the button is
pressed longer than 1.5 s, the scale switches to recalibration mode. The scale now measures the zero
point and waits to be loaded with at least ¼ of the maximum load. By briefly pressing the button the
weight displayed can be decremented or incremented in steps of 10g until the weight of the load placed
on the scale is reached. The direction can be changed by pressing the button longer. To stop
recalibration the button must be pressed longer than 5s. The scale can be switched off any time using
the on/off button or by not activating it for a while, thus aborting recalibration.
Optional functions (only DMS low-end module and SLC highend)
The functions “Tare“, “Hold“, “Autohold“ and “Replace weight in repeat measurements” can be
implemented via a program on the EEPROM. The functions are explained below:
Tare:
The tare function can be assigned to a button by the EEPROM program. If the button is pressed, the
weight is tared off as soon as the display has settled, if it is within the permissible range. Pressing the
button again alternatively switches the tare function off or causes the weight to be tared off again.
Hold and Autohold:
If the hold function is assigned to a button by means of the EEPROM, the weight reading is held on
display when the button is pressed as soon as the value has stabilized. Alternatively, the hold function
can be automated so that the weight will always be frozen when it has exceeded a certain threshold
and is stable.
The hold function is switched off after expiry of a predetermined time or by pressing the button again.
In addition the scale can be configured so that the hold function will be deactivated when the scale is
relieved, when the scale is relieved and then loaded again and / or when the load on the scale changes
significantly.
Replace weight in repeat measurements:
The scale can be configured so that the weight last displayed is displayed again in a measurement
when the scale detects that it has been loaded with almost the same weight.
Calibration
To ensure that the module functions properly, data must be written to the EEPROM before the module
is calibrated. Values that are only determined during the calibration process can be set to 0. The
correct figures will then be set after calibration.
If the weight is to be calculated using a third order polynomial, the scale must be calibrated using at
least four test loads. In order to increase accuracy, it is recommended to use even more weights.
If you wish to configure individual temperature compensation, the scale must be measured with a load
and without a load at temperatures on different ends of the range. In order to determine the square
term for slope compensation, the scale must also be measured at an average temperature.
To determine the required calibration values, please refer to the relevant documentation for EEPROM
programming.
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