CHAPTER 1. INTRODUCTION

TM 11-6625-298-14

CHAPTER 1

INTRODUCTION

Section I. GENERAL

1-1. Scope

reports which are to be used by maintenance

personnel at all maintenance levels are listed in

a. This manual describes Ohmmeter ZM-21/U,

and prescribed by TM 38-750.

ZM-21A/U, and ZM-21B/U (ZM-21 (*)/U) and its

b. Report of Packaging and Handling

operation,

functioning;

and

operator,

Deficiencies. Fill out and forward DD Form 6

organizational, and general support maintenance.

(Packaging Improvement Report) as prescribed in

There is no direct support maintenance authorized

AR 700-58/NAVSUPINST 4030.29/AFR 71-

for this equipment.

13/MCO P4030.29A, and DSAR 4145.8.

b. A list of references is contained in appendix

c. Discrepancy in Shipment Report (DISREP)

(SF361). Fill out and forward Discrepancy in

c. The maintenance allocation Chart (MAC)

Shipment Report (DISREP) (SF 361) as prescribed

appears in appendix C.

in AR 55-38/NAVSUPINST 4610.33A/AFR 75-

1-2. Indexes of Publications

18/MCO P4610.19B, and DSAR 4500.15.

a. DA Pam 310-4. Refer to the latest issue of

1-4. Administrative Storage

DA Pam 310-4 to determine whether there are new

For procedures, forms, records, and inspections

editions, changes, or additional publications

required during administrative storage of this

pertaining to this equipment.

equipment, refer to TM 740-90-1.

b. DA Pam 310-7. Refer to DA Pam 310-7 to

determine whether there are modification work

1-5. Destruction of Army Materiel

orders (MWOs) pertaining to this equipment.

Demolition and destruction of electronic equipment

will be under the direction of the commander and

1-3. Forms and Records

in accordance with TM 750-244-2.

a. Reports of Maintenance and Unsatisfactory

Equipment. Maintenance forms, records, and

Section II. DESCRIPTION AND DATA

external connections. On the top is a handle and a

1-6. Description

hinged protective cover for the meter window

a. Ohmmeter ZM-21/U, ZM-21A/U, and ZM-

glass. Printed on the back of the hinged protective

21B/U (fig. 1-1) are a self-contained, portable,

cover are condensed instructions for operation.

constant-voltage, insulation-resistance measuring

b. The test leads that come with the ohmmeter

sets (hereinafter referred to as ohmmeter). Figure

are six feet long with spade clips at one end and

1-1 illustrates ZM-21B/U, all other models are

spring clips at the other end. The spring clips are

similar in outward appearances. The ohmmeter

covered with rubber covers, one black and one red.

consists of a high-range ohmmeter of special

c. The carrying case is a gray, enamel-painted

design, a hand-operated, direct current (dc)

metal box (ZM-21/U and ZM-21A/U) with a

generator, a controller (controller in ZM-21A and

webbed carrying strap and two latches the

ZM-21B only), and a resistance network housed in

carrying case for the ZM-21B/U is made of plastic.

a bakelite case. Three terminals are provided for

1-1