CHAPTER 3. OPERATING INSTRUCTIONS

TM 11-6625-444-14-1

CHAPTER 3

OPERATING

INSTRUCTIONS

Section 1. CONTROLS AND INSTRUMENTS

sequently capable of a fully floating measurement

3-1. General

without degradation of accuracy.

This section describes overload protection and

b. Guarded measurements will be necessary

guarded measurement features of the voltmeter.

under the following conditions:

It also contains an illustration which locates and

(1) Long signal leads together with a high

describes each control, connector and indicator.

source impedance.

3-2. Damage From Improper Settings

(2) During floating measurements when

The voltmeter is fully protected from overloads

common mode voltage is at a high potential, high

applied to the input terminals in all ranges and

frequency, or both conditions exist.

modes of operation. In the VDC and RATIO

(3) During operation of the voltmeter in the

functions, ± 1100V DC or RMS (1500V peak to

presence of high level, radiated noise, an example

peak) can be applied to the input without dam-

of which is stray fields at the powerline frequency.

aging the volt meter. Potentials of up ± 150 vdc

c. Under normal op crating conditions (absence

can also be applied to the external reference input

of common mode signals), the GUARD terminal

terminals without damaging the voltmeter.

in the input terminal group shall be connected to

3-3. Guarded Measurements

the LO terminal. A slide strap is provided at the

GUARD terminal for convenience in connection.

a. A system of internal shields and guards

NOTE

Breve been included in the design and construction

INPUT terminals on the front panel and

of the voltmeter. These shields and guards can be

rear panel are connected in parallel.

connected as shown in figure 3-1 to minimize

Always check both terminal groups to

common mode-to-normal mode signal conversion

insure desired connections are made.

and induction o f n o i s e . T h e resulting

measurement process in the voltmeter is sub-

3-1