Operating Section - RCA WV-38A Operating And Maintenance Instructions Manual

RCA Volt-Ohm-Milliammeter
Operating Section
Zero Setting of Pointer
The pointer of the meter must indicate zero when the W V - 3 8 A is i n
the normal operating position. If the pointer does not indicate Zero, the
adjustment screw located at the lower center of the meter cover should
be readjusted.
Use of Range and Meter Scales
The meter scales on the W V - 3 8 A have been designed to provide
ease of operation and quick readability over a wide range of measure-
ments. Scales have been grouped according to the type of measurement
for which they are used.
Because of the wide number of measurement ranges provided on
the W V - 3 8 A , it is often possible to take voltage or resistance readings
on two ranges and scales. F o r greatest accuracy in voltage and current
measurements, always use the range which will provide an on-scale
reading which is nearest to the full-scale point. F o r example: 48 D C
Volts can be read from either the 50 Volt or the 250 Volt range. Because
the 50 Volt range will provide a reading nearest the full-scale point, the
50 Volt range only should be used if a reading of best accuracy is to be
obtained. T h i s general rule applies to all A C and D C Voltage ranges.
For resistance measurements, however, the range selected should be the
one which provides a reading nearest the center of the scale, because the
W V - 3 8 A provides the most accurate Ohms readings at mid-scale points.
For some measurements it will be necessary to use a multiplying
factor with the scale to obtain the correct reading. The required multi-
plication is indicated by the setting of the range switch. F o r example:
when the range switch is set to the 1000 V . position for voltage measure-
ment, the 0 to 10 scale is used, but the reading is multiplied by 100 times.
C A U T I O N :
When making voltage or current measurements, it is good practice
to make a trial measurement at a higher range setting than is consid-
ered necessary, because repeated overload may destroy the meter move-
ment or impair the accuracy of indications.
It is also good practice for personal protection to turn off all power
to the circuit under test when connecting or disconnecting the test leads.
T h e power to the circuit under test must be turned off when in-circuit
resistance measurements are made, otherwise damage to the W V - 3 8 A
may result.
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