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M-142 Multifunction Calibrator
MEATEST, s.r.o.
72
User Manual v54
The calibrator’s built-in generator generates a sine wave with voltage-controlled amplitude. The frequency is
derived from microprocessor control circuit’s crystal oscillator. The signal is fed to 20 V or 200 V amplifier and
then to output terminals. Feedback circuits sense the voltage present at the output terminals, normalize its value
and detects it. This results in a signal corresponding to average value of the output voltage. This signal is further
filtered and compared to the set value of output voltage. The error value controls the amplitude of the generator’s
output.
20mV and 200 mV voltage ranges
20 mV and 200 mV voltage ranges are derived from 2 and 20 V voltage ranges.
The output of the amplifier is fed to an inverting attentuator with 1:100 nominal division ratio. The signal is then
led to the output terminals, sensed via local feedback. This connection allows to load the calibrator output with
output current of several mA without losing accuracy.
1000 V AC, DC voltage range
The highest voltage range of the calibrator uses 200 V amplifier. It is connected to a pair of transformers with ca
1:6 transformation ratio.
In 1000 V AC mode, the output of 200 V amplifier is transformed and led to the output terminals. The output
voltage is sensed, rectified and compared to reference DC voltage provided by the DA converter. error value
controls the amplitude of the generator’s output so that there is correct voltage at the output terminals.
In 1000 V DC mode, 12 kHz signal is transformed, rectified, filtered and led to the output terminals. The output
voltage is sensed equally to 1000 V AC mode.