Description Of The Functions; Operating Principle; Block Diagram - Sartorius Portable Series Service Manual

SARTORIUS Portable and Gold

Description of the Functions

Operating Principle

Balances/scales of the model series PT...-000V1 and GT...-G00V1 feature a weighing system that consists of a
spring body with four strain gauges glued to the body. These strain gauges constitute a Wheatstone bridge which is
supplied with a reference voltage of + 5 V. When a load is placed on the balance/scale, the spring body is bent
slightly. In the process, two of the four strain gauges are compressed, and the other two are stretched. This results in
a change in resistance and, consequently, a change in voltage which is proportional to the load applied on the
weighing pan. This voltage is transmitted to the summing point of the A/D converter via amplifier IC106, low-pass
filter IC102 and resistor R120. In the A/D converter, consisting of:
AD3 IC104,
resistor R120 (measuring voltage at the summing point)
resistor R134 (reference voltage at the summing point)
and
capacitor C119 (integration capacitor),
a digital measuring result is generated by the stabilized voltage from low-pass filter IC102. This result is transmitted to
the balance/scale microprocessor IC107, which directly calculates the weight value according to the weight unit
selected and outputs this value on the display.
Balance/scale-specific data, parameters, and the calibration weight are stored in the EEPROM IC109.
Via a built-in data interface (option), you can directly transfer data to a peripheral (PC, etc.).

Block Diagram

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