Operation
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Flashing Display – Input Low
In var 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 cannot be guaranteed. If
the input falls to a value too low to actually permit a measurement,
the display will indicate "Input Low".
Hold Mode
When making measurements using any of the operating modes of
the 918B, you can "freeze" the values for all measured parameters
by simply pressing the "HOLD" button. You can then switch be-
tween all of the different modes and determine their respective
values at the time "HOLD" was pressed. Pressing "HOLD" a second
time restores the instrument to normal operation.
Min / Max Readings
Recording of minimum and maximum values is suspended for any
period of time that the hold function is active. However, all
previously recorded values are retained. Refer to section 3.2 for
more information on minimum and maximum value recording.
2.8 Measurement of Watts (Active Power)
The active power in an ac circuit is measured in watts, and is
defined as the product of the rms voltage, the rms current, and the
cosine of the phase angle between the two. Using the supplied
1000:1 current transformer, the 918B is capable of measuring active
power values of up to 20,000 watts. (For instructions on using other
current transformers with different ratios, refer to section 2.2.1.1).