XT2640 Operating Manual
13 July 2016
Page 44 of 187
This setting can be used in combination with the DIGITS setting (see below) to reduce the jitter in readings from unstable
signals.
12.4.2.3.3
Setting
the
Maximum
Number
of
Displayed
Digits
The DIGITS button allows you to select that all available measurement results will be displayed with limited resolution if desired.
Settings of 3, 4, 5 and 6 are available.
Recommendation:
In most applications this should be set to 5 or 6, if there is significant instability in the signals this should be set to 3 or 4.
Note:
This only affects displayed numerical results; it does not affect any measurements obtained via an interface or via a
historically saved record or via data logging.
12.4.2.3.4
Adjusting
Measurements
for
V
or
A
Terminal
Burden
The ADJUST button allows you to select that results of each channel are adjusted to compensate for either the current drawn by the V
terminals or for the voltage between the A terminals.
The labelling of each selection shows whether you need results at the source or at the load, followed (in braces) by whether the V
terminals of each channel are connected at the source or the load.
If you select NONE then no adjustments are performed, the results use the unadjusted voltage and current signals.
If you select SRCE(V@SRCE) then the V terminal current burden is added to the A signal. This should be used when the V
terminals are directly connected across the source voltage (so the A terminals are measuring the load current) and you
wish to obtain the source results.
If you select SRCE(V@LOAD) then A terminal voltage burden is added to the V signal. This should be used when the V
terminals are directly connected across the load voltage (so the A terminals are measuring the source current) and you
wish to obtain the source results.
If you select LOAD(V@SRCE) then the A terminal voltage burden is subtracted from the V signal. This should be used when
the V terminals are directly connected across the source voltage (so the A terminals are measuring the load current) and
you wish to obtain the load results.
If you select LOAD(V@LOAD) then the V terminal current burden is subtracted from the A signal. This should be used
when the V terminals are directly connected across the load voltage (so the A terminals are measuring the source current)
and you wish to obtain the load results.
Recommendation:
In most applications this should be set to NONE; only if not using external current transducers and either operating at low
voltages and high currents or at high voltages and low currents should this be set for an adjustment to be applied.
See section 18 for full details regarding configuring this for EN61000‐3‐2 and ‐12 measurements.
Note:
Channels which have scaling applied ignore the ADJUST setting and their signals are not adjusted.
12.4.2.4
CONFIGURING
HOW
RESULTS
ARE
COMBINED
This is performed by using the buttons in the COMBINE area.
Depending on configuration and the installed channels not all buttons may be present and the COMBINE area itself may not present.
12.4.2.4.1
Setting
How
the
Channels
are
Wired
The WIRING button allows you to select how measurements are combined and labelled when producing total results for this VPA.
The selection made must match the method used to wire the application to the XT2640 channels in this VPA.
Note:
The available selections are determined from the number of channels selected in this VPA. If the number of channels is
altered then this setting will be reset to the N x 1ø setting (which is valid for any number of channels).
12.4.2.4.2
Setting
How
Power
will
be
Included
in
Efficiency
and
Power
Loss
The EFF/LOSS button allows you to select how the total power of this VPA is included in efficiency and power loss data.
This button is not available if MEAS MODE is set to SINGLE VPA or SPECTRUM.
The XT2640 allows the total watts of a VPA to be included in one of three available data; IN, MIDDLE and OUT power. Alternately the
total power of this VPA can be excluded from all three of these.
Note:
If the XT2640 is configured as part of a multi‐unit group then the resulting IN, MID, OUT power totals, power loss and
efficiency results will include the total IN, MID and OUT power measurements from all XT2640s within that multi‐unit
group.
12.4.3
CONFIGURING
MECHANICAL
MEASUREMENTS
(MOTOR
OR
GENERATOR)
If a MT type channel is installed in the CH4 location then the CONFIG VPA button is always shown and allows you to select whether a
VPA or the MOTOR measurements are to be configured.
The example screen shown below is an example of the MOTOR configuration screen.
