PSM1700 PsimetriQ user manual
9-1
9 Input channels
The two input channels are differentially isolated from each
other and from earth, and are controlled independently but
sampled synchronously.
Each input channel may be selected to be:
disabled
voltage
external shunt
If the external shunt option is selected, the data is scaled
by the shunt value (entered under the relevant channel
menu) and the units are displayed in Amps. Any resistor
can be used as a shunt, or precision low inductance
current shunts are available as accessories. Current
transformers can be used if fitted with an appropriate
burden resistor.
Note that the external shunt input polarity is
reversed compared to that of the voltage input: ie
the outer screen of the input connector is positive
and the inner contact is negative. This is so that the
capacitance to ground of the probe cable screen is driven
with the lower source impedance in order to minimise
errors at high frequency.
Note that some modes force the input channels to be
voltage or current automatically, eg. the power meter
defaults to channel 1 as voltage and channel 2 as current.
This automatic selection can be overridden if required.
The input ranges have nominal full scale values set with a
ratio of 1:10 from 10mV to 100V. This gives the following
ranges: