Page 16 - Voltech Instruments PM3300 Universal Power Analyser, designed and produced by Connell Marketing Associated, 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 3.5 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 block (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) and thermal printer (12).
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