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Operation
35
Procedure
1.
Switch the instrument to the phase mode by pressing "PHASE".
Connect the output of the clamp-on current transformer (CT) to
the current input of the 918B, using the supplied cable.
2.
Be sure that the (+) and (-) terminals on the CT correspond
directly to the (+) and (-) terminals of the 918B current input.
Clamp the CT around the wire carrying the current to be
measured, making certain that the jaws close completely.
3.
Note the (+) and (-) symbols and the arrow, indicating the phase
relationship between the CT input and the CT output. 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 phase value displayed on the 918B will be
zero. Figure 3 illustrates the relationship between voltage lead
polarity and current transformer orientation.
4.
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.
5.
Connect the black lead to the circuit neutral or ground, or the
point to be used as the reference for the measurement.
6.
Connect the red test lead to the voltage to be measured. The
value of the phase angle between the voltage and current in the
circuit under test will be displayed, in accordance with the
selected phase convention.
Flashing Display – Input Low
For the phase angle mode, minimum values of voltage and current
must be present at the inputs to maintain accuracy. The 918B
display will indicate when the voltage and/or current fall below their
minimum values. If an input value falls below the bottom of the
lowest range in auto-range mode, or below the bottom of a held
range, the display will begin to flash. Measurements can still be
made, but the input is outside of its specified range and accuracy