Page 12 - Voltech Instruments PM3000A Universal Power Analyser, designed and produced by Connell Marketing Associates, UK

Functional Description

The voltage inputs are attenuated by the 1Mohm precision dividers (1) and the
current inputs are converted to low level voltages by 12.5 mohm precision shunts (2).
The current channels may alternatively be fed directly with low voltage signals at the
EXT inputs.
Each low level signal is buffered and amplified by programmable gain amplifiers (3),
the gain being set by the processor according to the range selected.
The outputs from the amplifiers are filtered (4) to avoid alias components, then
converted to digital information by fast A to D converters (5). The converters scan all
six channels simultaneously, the rate of scanning being set by the processor
according to the frequency of the input signals.
The data from the A to D converters is transmitted through digital isolation transformers
(6) providing a high degree of electrical isolation. This allows all the inputs to float with
respect to each other and with respect to ground greatly simplifying accurate
measurements.
The digital information is transferred to the computation processor (7) which
computes the value of the required measurements. These values are then passed
to the interface processor (8) which provides control of the instrument from the
interfaces (9) or keyboard (10) and presents the measurement results on the vacuum
fluorescent display (11).
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