5.2.6 Peak Volt Overload Indicator
This indicator may be used to alert the user to the presence of spikes on the input signal. If the
peak or steady-state voltage applied to the load is greater than 250% of the range selected with
the Voltage Range Key, the "Volts O/L" indicator will be illuminated. Select a higher voltage
range or reduce the supply voltage to extinguish the LED. Volts and power displays may or may
not be correct and should not be trusted if this indicator is lit.
5.2.7 Amps-Volts Display
When the Volts Display Indicator is ON, the right-hand digital display will show the True RMS
(AC+DC) voltage applied to the rear panel connectors.
When the Amps Display Indicator is ON, the True RMS (AC+DC) current passing through the
internal shunt will be displayed in the right-hand display.
A flashing display in either mode indicates an overload condition. Reduce inputs or increase the
ranges until a stable reading is observed.
5.2.8 Watts – True Power Display
The power dissipated in the load (in watts) is indicated on the left-hand display. This reading is
invalid if either the amps or volts overload indicator is illuminated. These peak indicators occur
independently of whether "Amps" or "Volts" has been selected for the right-hand display. In
either case, select a higher range or reduce the input signals. If the highest range has been
selected and a peak O/L indicator is still on, the measurement may require the use of external
dividers and/or current shunts.
This display includes a polarity (-) sign which indicates the general phase relationship between
the voltage and current. A negative sign indicates that the voltage and current are out of
phase. The lack of a negative sign means that the voltage and current are in phase. Note that a
negative sign may also indicate that the voltage or current leads are reversed. The polarity sign
may also be used to determine source or load power. Load power is that power which is
consumed by a load. Source power (-) is that power which is supplied by a source.
If external dividers or shunts are used, the power display will be a fraction of the actual load
power. Simple ratio calculations will then reveal the power actually delivered to the load. See
Section 5.4.2.
Under certain conditions where complex waveforms are being applied to the load, it may be
necessary to select a current and/or voltage range that is well above the true RMS value
indicated on the display in order to extinguish the "O/L" indicator. This will reduce the
resolution of the wattmeter reading, but is necessary for instrument accuracy. The display will
blink if the load power is greater than that required for a display of 19999 (decimal omitted).
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