B&K Precision 1655A - Manual - Manual (Page 25)

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LOAD MEASUREMENT PROCEDURE
Measurement of electrical load is extremely simple when using
the Model 1655A or 1653A AC Power Supply as the power
source. Refer to Fig. 11. The built-in meter may be switched to
measure the voltage and current being delivered to the equipment
under test. Multiplying the voltage times the current give the
electrical load in volt-amps.
For Model 1655A the calculations is not even required if the
measurement is made at the standard value of 120 volts. The
0-2A and 0-4A current scales are also calibrated as direct reading
0-24VA and 0-480VA scales.
NOTE
The VA scales are accurate only at 120 volts. At other voltages,
use the 0-2A or 0-4A current scales and calculate the electrical
load by multiplying output voltage times output current.
SERVICING APPLICATIONS
An initial check of electrical load can often give a clue to the
problem when troubleshooting electronics equipment. If the
equipment under test is drawing considerably less current than
normal, perhaps one of the power supply voltages is absent,
disabling several circuits. If current is higher than normal, a
transistor or other component may be shorted. If current remains
higher than normal after other faults have been corrected, a leaky
filter capacitor is suspected. Such problems should be corrected
to prevent another impending failure.
The normal electrical load or current drain for the equipment
under test is usually specified in its servicing literature. If that
information is not available, the normal current drain is typically
60% to 80% of the rated current of the circuit breaker or line fuse.
DESIGN APPLICATIONS
The design goals of any ac powered electronic product include
input power requirements. Using the ac power supply as the
power source for breadboard and prototype units provides
continuous monitoring of electrical load for various circuit
configurations, at various input voltages, and at various
temperatures.
PRODUCTION TESTING
Final testing of electrical and electronics equipment nearly
always includes monitoring of electrical load in all modes of
operation. The B+K Precision ac power supplies provide both
variable voltage and electrical load measure meant capabilities
needed in such a test station.
ENERGY EFFICIENCY
Energy efficiency has become an important consideration in
equipment selection. Equipment with the least electrical load is
the most energy efficient. The electrical load of similar products
can be compared side by side, demonstrating energy efficiency to
a customer in terms readily understood by a layman.
OPERATING INSTRUCTIONS Troubleshooting: Load Measurement
TROUBLESHOOTING: USING THE AC POWER SUPPLY TO MEASURE ELECTRICAL LOADS