S e c t i o n 1. BLOCK DIAGRAM ANALYSIS

TM 11-6625 -537-14-1

CHAPTER

FUNCTIONING

EQUIPMENT

S e c t i o n 1. BLOCK DIAGRAM ANALYSIS

5-1. General

power supply and a voltage divider. The 500-volt

(fig. 5-1)

power supply is a conventional series-regulated

supply with a single regulation stage. The output

Electronic Voltmeter ME-202 (*)/U is a precision

of the supply is set to 500 volts by using the dc

voltmeter used to accurately measure ac or dc

vtvm to compare a precise sample of the output

potential between O and 500 volts, It basically

voltage with the voltage of standard cell B 1. The

consists of a dc vacuum tube voltmeter (vtvm, a

500-volt power supply also provides B + to the

O- to 500-volt dc reference, a null and range

ac-to-dc converter.

divider, an ac-to-dc converter, and a low voltage

c. Null and Range Divider. The null and range

supply. T h e s e units are shown in the block

divider selects the magnitude of input voltage to

diagram and are discussed in a through e below.

the de vtvm. The output of the divider is con-

The electronic voltmeter functions as a con-

trolled by the RANGE and NULL switches.

ventional vtvm when the NULL switch is set to

d. Ac-to-Dc Converter.The ac to dc converter

VTVM, and as a differential voltmeter when the

converts all ac input voltages to a dc voltage

NULL switch is set to 10, 1, .1, or .01. The

which is proportional to 1.11 times the average

functioning o f the electronic v o l t m e t e r is

value of the input waveform. If the input ac is of a

presented in paragraphs 5-2 through 5-6. The

single frequency, the dc output of the converter

explanation is supported by block diagrams and

will be proportional to the root-mean-square (rms)

partial schematic diagrams. See figure FO-6 for a

value of the input. The converter provides a dc

complete schematic diagram of the electronic

output of 5 volts when full range voltage is ap-

voltmeter.

plied to the electronic voltmeter in each range.

a. Dc Vtum. The dc vtvm indicates the dif-

The output of the converter is applied to the dc

ference between the input voltage and the O- to

vtvm in the vtvm mode of operation, or compared

500-volt dc reference in the electronic voltmeter

to O- to 500-volt dc reference in the differential

mode. In the vtvm mode, the dc vtvm indicates

voltmeter mode.

the value of the unknown voltage directly on the

e. Low Voltage Supply. The low voltage supply

VOLTS meter.

provides B + to the dc vtvm and filament voltage

b. O- to 500-volt Dc Reference. The O- to 500-

as required.

volt dc reference is obtained from a 500-volt dc

5-1

Figure

5-1.

Electronic

Voltmeter

ME-202(*)/'U,

block

diagram.