TM 11-6625-298-14
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)
A.
(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
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
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
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.
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
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
