TM 9-4935-282-34
803D
CONTROLS
TERMINALS
LOCATION
CIRCUIT
FUNCTIONAL DESCRIPTION
AND
SYMBOL
INDICATORS
NULL switch
Front panel
S3
Set to VTVM for determining the approximate value of unknown
voltage prior to differential measurements. Five null switch
ranges of 10, 1, 0.1, 0.01, and 0.001 volts are used for
differential measurements. For the DC mode, the null ranges
represent full scale differences between the unknown voltage
and the amount of precision internal reference voltage that is
set on the voltage readout dials. For the AC mode, the null
range used times the applicable AC Null Multiplier, indicated by
the range switch, represents the full scale difference between
the unknown voltage and the amount set on the voltage dials.
A, B, C, D, and E
Front panel
S6, S7,
Provide an in-line readout of the amount of in-
voltage readout
S8, S9,
ternal reference voltage necessary to null the un-
dials
S10
known voltage.
Decimal lights
Front panel
DS1, DS2,
Serve as decimal points for the voltage readout
DS3, DS4
dials. A different light illuminates for each position of the
RANGE switch.
AC - DC polarity
Front panel
S5
Selects the AC, + DC, or - DC mode of operation.
switch
With this switch in the positive position, the polarity of the upper
input binding post is positive with respect to the lower input
binding post (middle post).
Output terminals
Rear panel of
J4, J5
Provided for attaching a recorder to monitor volt-
cabinet models,
age excursions.
front panel of
rack models.
Output level
Rear panel of
R1
Varies the output level of the output binding post
control
cabinet models,
from 0 to at least 18 millivolts full scale deflec-
front panel of
tion.
rack models.
Meter
Front panel
M1
Indicates approximate voltage when 803D is in VTVM mode
and difference between unknown and internal reference voltage
when 803D is in differential mode. The upper scale, 500-0-500,
is used when the NULL switch is set to VTVM at all other times,
the lower scale, 1-0-1, is used.
Mechanical zero
Meter case
None
Sets meter to zero mechanically. This adjust-
control
ment should be used only after instrument has been turned off
for at least three minutes or when the internal meter terminals
have been shorted.
Fuse
Rear panel of
F1
Fuse holder protrudes from instrument to provide
cabinet models
easy access to the fuse. The fuse is a 1.5 ampere
front panel of
slow blowing type for 115 volt operation and a
rack models.
0.75 ampere slow blowing type for 230 volt operation.
Figure 2-1. CONTROLS, TERMINALS, AND INDICATORS (sheet 2 of 2)
2-2
