Figure 3-2. Dc Vtum ranges.

TM 11-6625-537-14-1

3-2. Select 500 volt range if value of voltage to be

3-7. Operating Procedures

measured is unknown.

a. Operation a s a Conventional D C V t u m

(4) Connect voltage to be measured to input

(Accuracy Within 3 Percent of Meter Reading).

terminals. Connect grounded side of input to

Dc voltages between O and 500 volts may be

lower input terminal.

measured with the electronic voltmeter used as a

( 5 ) Read voltage from upper or lower

conventional vtvm. Perform procedure in ac-

VOLTS meter scale as required by figure 3-2. A

cordance with paragraph 3-5 and proceed with the

VOLTS meter deflection to the left indicates that

following steps:

polarity of dc voltage is opposite that of the input

(1) Set voltage readout dials A, B, C, D, and

terminals as indicated by the AC-de polarity

E to O.

control.

(2) Set AC-dc polarity switch to +

(6) Set NULL switch to VTVM and

(positive).

disconnect voltage from input terminals.

(3) Determine input voltage range and set

NULL and RANGE controls as specified in figure

Input

VOLTS

RANGE

NULL

VOLTS Meter

Meter

voltage

FUll Scale Deflection

Setting

Range

Scale

VTVM

Upper

500

0 to 500v dc

500-0-600

VTVM

50-0-50

Upper

0 to 50v dc

Any

10-0-10

Lower

*0 to 10v dc

VTVM

5-0-5

Upper

0 to 5V dc

Any

1 -0-1

Lower

*0 to 1v dc

Upper

VTVM

0 to 0.5v dc

0.5-0-0.5 (500mv)

Any

0.1-0-0.1(100mv)

Lower

*0 tO 0.1 v dc

Any

.01

Lower

0.01-0-0.01(10mv)

* O 1o O.01 v dc

*All five voltage readout dials must be set to O to utilize this range.

EL6625-537-14-TM-5

Figure 3-2. Dc Vtum ranges.

deflection. N o t e t h e a p p r o x i m a t e v a l u e o f

b. Operation as a Differential Dc Voltmeter

unknown voltage as indicated on upper VOLTS

(Accuracy Within 0.05 Percent of Voltage

meter scale,

Readout Dials). The electronic voltmeter is used

as a differential dc voltmeter by comparing the

(4) If VOLTS meter deflects to the left,

unknown voltage with a known internal voltage.

the unknown voltage is negative. Set AC-de

When the two voltages are equal, the VOLTS

polarity switch to (negative). VOLTS meter

meter will indicate zero. The magnitude of the

deflects to the right.

i n t e r n a l voltage is controlled by the voltage

(5) Set voltage readout dials A and B to

readout dials and is indicated by the voltage dial

correspond to the approximate value determined

indicators. The value of the unknown voltage may

in (3) above, and set dials C, D, and E to O.

A B (RANGE switch)

Examples:

b e read directly on the indicators when the

Voltage

492 V dc

500

VOLTS meter indicates zero. When adjusting the

155 V dc

500

v o l t a g e readout dials, VOLTS meter needle

65 V dc

500

deflection to the right indicates that the unknown

35 V dc

voltage is greater than the internal voltage and

2.1 V dc

0.125 V dc

the voltage readout dials should be increased. The

voltage readout dials should be decreased if the

NOTE

VOLTS meter needle deflects to the left.

Set voltage readout dials slightly below

(1) Perform initial operation in accordance

the approximate value as indicated in the

with paragraph 3-5.

example.

(2) Connect unknown dc voltage to input

(6) Set NULL switch to 10.

terminals. Connect grounded side of input to

(7) Advance voltage readout dial B until

lower input terminal (middle terminal).

VOLTS meter needle deflects to left and then

back one step to return needle to right side.

(3) Set RANGE control to lowest position

that will allow an onscale VOLTS meter

(8) Set NULL control to each succeeding

3-6