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2.4.2 2.4.1.1 Entering Voltage
To establish a voltage setting for the wattmeter under test voltage coil, the Model 800A status
LED "Key Voltage" must be illuminated. If it is not illuminated push the reset button located on the
Keypad.
The voltage may now be keyed in. Any integer value from 10 to 749 volts may be entered.
Other values will be ignored and the Error LED will be illuminated. The value of each digit appears in
the Volts display as the keys are pressed. The voltage in the display is applied to the internal circuits
of the Model 800A when the third digit is keyed in and the voltage field is filled. If only two digits are
required (e.g. 15 or 30 volts), the Enter button located on the keypad must be pressed. Thereafter
the Enter Volts LED is extinguished and the Key Volt-Ampere LED is illuminated.
2.4.3 Entering Volt-Ampere
The volt-ampere setting is entered via the keypad and appears in the Volt-Amperes display.
Any integer value may be applied as long as the corresponding current is 50 amperes or less (75
amperes optional). Other values will be ignored and the Error LED will be illuminated. The value is
applied into the internal circuits after the 5th digit is keyed or after the Enter button of the keypad is
pressed. Immediately after the entry of the volt-ampere value, the corresponding output current is
calculated and shown in the Current display.
2.4.4 Applying Excitation
The Model 800A is now ready for application of power to the wattmeter under test. Press the
Operate button momentarily. The red LED above the button should be illuminated. If the excitation
current to the voltage coil or the excitation voltage to the current coil exceeds limits which might
cause inaccuracy, the Model 800A automatically reverts to the Standby state. The Overload LED is
also illuminated. The connections to the wattmeter or its loading characteristics should be checked.
The overload indicator may be illuminated when power is applied to the 800A (due to momentary
transients), but it will be extinguished upon an Operate command under normal conditions.
2.4.5 Power Factor
When not in use the Power Factor selector should be set to 1 PF. When in use any power
factor between zero lagging and zero leading may be chosen in .1PF steps. The Power Factor
selector advances or retards the current with respect to the voltage however it does not affect the
Volt-Ampere display. The Volt-Ampere display shows the power delivered at unity power factor.
2.4.6 Fractional Setting
The Fractional Setting control applies an excitation to the wattmeter which is the product of
the Volt-Ampere display times the setting of the control at 1 PF only. For example, if the Volt-Ampere
display is 1000 Volt-Amperes and the Fractional Setting control is set to 4/5, 800 Volt-Amperes is
applied to the wattmeter under test. That is, the current is reduced to 4/5 of its previous value. The
feature is useful for cardinal point testing of analog meters with non decimal scales.
2.4.7 Deviation Function - Error Measurement
If a wattmeter has an error, it will indicate an erroneous reading. The Deviation controls may
be used to measure the error. Select a deviation scale appropriate to the wattmeter under test.
Adjust the Deviation control so that the wattmeter reads exactly the volt-ampere value displayed on
the Model 800A - or the volt-ampere value times the Fractional Setting value - or the volt-ampere
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