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Operation
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1.
To perform var measurements with the 918B, switch the
instrument to the var mode by first pressing "SHIFT", then
pressing "VAR".
2.
Connect the output of the clamp-on current transformer (CT) to
the current input of the 918B, using the supplied cable. Be sure
that the (+) and (-) terminals on the CT correspond directly to
the (+) and (-) terminals of the 918B current input.
3.
Clamp the CT around the wire carrying the current to be
measured, making certain that the jaws close completely. Note
the (+) and (-) symbols and the arrow, indicating the phase
relationship between the CT input and the CT output.
4.
If a current flowing in the same direction as the arrow is exactly
in phase with a voltage present on the (+) voltage lead (with
respect to the (-) voltage lead), the var value displayed on the
918B will be zero. Figure 3 illustrates the relationship between
voltage lead polarity and current transformer orientation.
5.
Plug the supplied test probes into the voltage input terminals,
with the red wire connected to the (+) terminal and the black
wire connected to the (-) terminal.
6.
Connect the black lead to the circuit neutral or ground, or the
point to be used as the reference for the measurement.
7.
Connect the red lead to the voltage to be measured. The value
displayed will be the volt amps reactive for the circuit under test.
Operating Ranges
For voltage inputs, the 918B has four different operating ranges. For
current inputs, the 918B has three different operating ranges.
Depending on the levels of voltage and current applied to the inputs,
the instrument may automatically switch between ranges. This range
switching is internal, and may or may not be evident in the display.
Automatic range switching can be defeated, using range hold. Refer
to section 3.1, "Automatic and Manual Range Selection", for a