Calibration Check

TM 11-6665-232-40

3-2. Continuity

NOTE

If the radiacmeter is equipped with an

Continuity of wires used in the IM-174A/PD can be

instrument light, press the lamp switch, and

checked either by inspection or by using an ohmmeter

then release it. The lamp should light when

(AN/USM-223). Refer to the wiring diagram (figure

the switch is pressed, and the lamp should

3-5 or 3-6) to determine where wires are connected.

extinguish when the switch is released. If the

Inspect each wire closely moving it slightly back and

lamp does not light, replace the lamp and/or

forth to determine if the wire is broken under its

the battery (TM 11-6665-232-12).

insulation, When wires are laced or otherwise formed

(3) Press and hold the function switch to ZERO

into a cable, use an ohmmeter to check continuity.

and adjust the zero control until the meter indicates 0.

Locate each end of the wire to be checked on the

(4) Release the function switch to the operate

wiring or schematic diagram and measure the

(center) position; the pointer of the meter should

resistance of the wire. A low or zero resistance

swing upscale between 5 and 10 rad/hr, and then fall

measurement indicates a good wire. Any other value

back to 0.

measured indicates a trouble which will require

(5) Press and hold the function switch to

further investigation.

CHECK. The pointer of the meter should indicate

3-3. Calibration Check

above the check band by 3 meter needle widths. Those

readings below the check band or higher than 3 needle

WARNING

widths must be replaced by a new battery.

Extremely dangerous radiation exists

WARNING

in the AN/UDM-2. Before performing the

Batteries BA-1006/U, BA-1391/U and BA-

calibration check of the radiacmeter,

1396/U used in IM-174A/PD contain

observe all precautions indicated in TM

mercury. These batteries can be hazardous if

11-6665-227-12.

not handled properly. There is a possibility

a. General. When used in the field, it is important

of the battery exploding or generating a toxic

that the readings obtained from the radiacmeter `are

gas when it is heated excessively. Do not

accurate. When a calibration check is being

throw mercury batteries into a fire, expose

performed, the radiacmeter is exposed to known dose

them to a high heat or short them out causing

rates of radiation contained in the AN/UDM-2. No

them to heat to a high temperature.

adjustment (other than operational) will be made to

the radiacmeter during the calibration check.

CAUTION

Mercury contained in Batteries BA-1006/U,

NOTE

BA-1391/U and BA-1396/U is hazardous to

During the electrical check (b below) and the

the environment. Where ver possible, dead or

calibration check (c below), the radiacmeter

expended batteries should not be discarded.

should be positioned so that the meter face is

They should be returned to depot through

up and parallel with the ground.

supply channels.

b. Electrical Check. Before the calibration check is

performed, check for normal operation of the

NOTE

electrical circuits of the radiacmeter by performing the

When in the CHECK mode, after new

test outlined below:

batteries are installed, some multibattery

r a d i a c m e t e r s will indicate above the

NOTE

CHECK band by 3 meter needle widths.

Perform the test in an area that is free from

Radiacmeters reading in the CHECK band

radiation.

or 3 needle-widths above are acceptable for

(1) Prepare the radiacmeter for use (TM

use. Those reading below the CHECK band

11-6665-232-12), but do not install the radiacmeter in

or higher than 3 needle-widths must be

its carrying case.

repaired or recalibrated.

(2) Turn on the radiacmeter by turning the zero

(6) Release the function switch to the oper-

control clockwise from OFF, Allow at least 2 minutes

for the radiacmeter to warmup; if time permits, allow

20 minutes for complete warmup.

3-2