PPA5xx/15xx user manual
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parameters. Even difficult applications such as lighting
ballasts can be easily addressed with the special modes’
application in the firmware of the instrument.
The whole operation of the instrument may be controlled
remotely via a serial interface (RS232/USB), or optionally
a LAN/GPIB interface.
The voltage and current channels are identical except for
the voltage attenuator and current shunt at the very front
end.
Each channel consists of a selection switch for external or
internal attenuator/shunt followed by a high impedance
buffer, then a series of gain stages leading to an A/D
converter. Selection of the input gain and the sampling of
the A/D converter are under the control of the DSP. There
is an autozero switch at the front end for dc accuracy. The
analogue circuitry is optimised for high linearity over a
wide dynamic range and high frequency performance.
The PPA5xx/15xx includes an “internal - x10” mode which
adds a x10 gain stage to the analogue amplifier chain. This
allows measurement of even smaller signals with the
caveat that the bandwidth is reduced to c. 100 kHz.
Both input channels are fully isolated with very good CMRR
and noise rejection.
The current shunt is of a proprietary design which gives
very wide bandwidth with minimum phase shift.
The voltage attenuator is of a proprietary design which has
a wide bandwidth response matched to that of the current
shunt.
Both the voltage and current channels are calibrated
digitally so there are no physical adjustments to be made.