
Operation
33
Procedure
To measure frequency with the 918B, first switch the instrument to
the frequency mode by pressing "FREQ".
If the frequency of the current in a circuit is desired, use the
following connection procedure:
1.
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, indicating the phase relationship
between the CT input and the CT output.
If the frequency of the voltage in a circuit is desired, use the
following connection procedure:
1.
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.
2.
Connect the black lead to the circuit neutral or ground, or the
point to be used as the reference for the measurement.
3.
Connect the red test lead to the voltage to be measured. The
value displayed will be the frequency of the voltage or current in
the circuit under test.
As stated above, if both the voltage and current inputs are used, and
signals are present at both, the instrument will default to displaying
the frequency of the voltage.
Flashing Display – Input Low
For the frequency mode, a minimum value of voltage or current
must be present at one of the inputs to maintain accuracy. The 918B
display will indicate when the voltage and/or current fall below their