Simpson 880 WATTMETER User Manual

Operating Instructions
Operating Instructions
3.4 TEST PROCEDURES
MODEL 880 VOLTMETER
To measure AC or DC voltage, connect leads to the binding
post marked ± and to the binding post with the desired voltage
range. The leads can then be connected to the test circuit. See
figure 9 for wiring diagram. It is not necessary to observe po-
larity when measurements are taken with the Model 880
Voltmeter.
When in doubt as to the correct voltage range to be used, always
start with the highest range of the Model 880 Instrument, so
as to afford a greater degree of protection to the unit.
3.5 TEST PROCEDURES-WATTMETER
MODEL 880 WATTMETER
A. SINGLE PHASE
To measure power in a single-phase circuit, only a single model
880 wattmeter is required.
Caution should be exercised to be sure the ± potential and ±
current terminal are connected to the same side of the line.
Diagrams are provided in this manual to aid the user in making
swift effective tests with the model 880 wattmeter.
B. THREE-PHASE, THREE WIRE
Wattage (power) measurement in a three-phase, three wire cir-
cuit balanced or unbalanced is accomplished by use of two
single-phase Model 880 wattmeters. See Figure 6 for wiring
diagram.
C. THREE-PHASE, FOUR WIRE
Wattage (power) measurement in a three-phase four wire cir-
cuit, balanced or unbalanced, is accomplished by use of three
single-phase Model 880 wattmeters. See Figure 8 for wiring
diagram.
Polarity must be observed as indicated in the following dia-
grams with regard to the marked binding post of each model
880 wattmeter used in a poly-phase test circuit. This is im-
portant since a base must be established to determine polarity
of the readings.
When the power factor in the circuit under test is less than
0.5, the reading of one- of the model 880 wattmeters will read
reverse. After re-checking to see that the connection polarity
of all the wattmeters are the same, the current coil leads of the
reverse reading unit should then be reversed. The indication
should now be up-scale. This up-scale value should be noted
and recorded as a negative quantity. This negative quantity
should then be added algebraically to the total positive sum
to obtain the true power dissipation of the circuit under test.
Example:
In a typical three-phase four wire circuit three model 880
wattmeters are used. Meter #1 produces an up-scale read-
ing of 500 watts.
Meter #2 produces a reverse reading. Re-check leads for
correct polarity before reversing leads to current coils.
The up-scale reading is now —400 watts. Meter #3 pro-
duces an up-scale reading of 475 watts.
Meter #1 = +500 watts
Meter #2 = —400 watts
Meter #3 = +475 watts
Algebraic Sum = +575 watts true power
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3-3

Simpson 880 WATTMETER Specifications

General

Brand	Simpson
Model	880 WATTMETER
Category	Measuring Instruments
Language	English