Measurement Procedure

Set RANGE-FULL SCALE control to .001 and carefully

adjust BALANCE control for minimum meter deflection.

Normal meter deflection for zero input signal is

as follows:

RANGE

DEFLECTION

.001

less than 3/4 inch

.003, .01, .03, .1, .3,

less than 1/16 inch

1, 3

Suppressed

3.3 Measurement Procedure

a. Set RANGE-FULL SCALE control to appropriate setting

(or higher) for voltage to be measured.

b. For "in-circuit" measurements, remove 500 Adapter and

attach Probe Tip to RF Probe. The Probe Tip is useful

for direct measurement to approximately 250 megacycles,

however, a short wire should be substituted for the

ground lead when using above 100 Mc to minimize the

effects of ground lead inductance. Above 250 mega-

cycles, the probe may be used directly without the

tip but the connecting leads must be extremely short

to avoid resonant effects, see Fig. 4.

c. Connect ground clip or wire to suitable ground and

connect tip to point where voltage is to be measured.

Alternatively measurement may be made using direct

connection (Fig. 4.).

Read RF voltage on appropriate meter scale corresponding

to setting of RANGE-FULL SCALE control.

To obtain readings in decibels, add the db (red scale)

meter reading to the db (red) setting of the RANGE-FULL

SCALE control. Although individual db readings have no

significance as absolute measurements, the difference

between two db readings is a useful way of expressing

voltage ratio.

For terminated measurements in

systems, the

Adapter should be attached to the RF Probe. Always

AN/URM-145