This specification covers panel mounted, electrical-indicating, milliampere, direct-current ammeters of the edgewise type.

The type designation of ammeters shall be in the following form, and as specified (see 6.1):

Ammeters covered by this specification are designated by the two-letter symbol "MR".

The style is designated by a one-letter symbol as follows:

V - vertical scale

H - horizontal scale

The size is designated by a one-number symbol representing the conventional identification and approximately equal to the case size in inches as follows:

5 - 5-inch case length

8 - 8-inch case length

The scale color scheme is designated by a one-letter symbol as follows:

W - white scale background, black markings

B - black scale background, white translucent markings

The full-scale value of single-range meters with zero at left for horizontal scale meters or at the bottom for vertical scale meters is represented by three figures designating the maximum number of units indicated; when the full-scale value is less than three figures, zeros are inserted at the left to fill out to three figures. Where the letter "R" is used in this group, between two figures, it represents a decimal point. Example: 1R5 represents 1.5.

The full-scale value of zero-center or offset zero meters is indicated by two numbers designating the numerical value of the end-scale points, with a letter between them designating the decimal value of the numbers, as follows:

D - tenths Example: 5D5 represents 0.5-0-0.5

U - units Example: 1U9 represents 1-0-9.

T - tens Example: 2T2 represents 20-0-20.

H - hundreds Example: 5H5 represents 500-0-500.

The kind of current for which the ammeters are designed is designated by two letters as follows:

DC - Direct current

Ammeters shall be furnished in the following full-scale ranges:

          Direct current ammeters
               Milliamperes

          1  10  100
          2  20  200
          5  50  500

Two letters that designate the electrical units indicated by the ammeters are MA-Milliamperes.

A two letter symbol designates special features as follows. An ammeter may have no special feature or one or two special features.

1st letter

O - no illumination

L - Internal illumination

2nd letter

O - no special marking

S - special scale marking, for example a non-electrical quantity such as gallons per minute or pounds per square inch.

Type MRV5W050DCMA00 signifies:

(a) MR - Ammeter

(b) V - vertical

(c) 5 - 5-inch case size

(d) W - White scale

(e) 050 - Zero bottom, full-scale value of 50.

(f) DC - direct current

(g) MA - Milliampere

(h) O - no illumination

(i) O - no special marking

Type MRH8W005DCMALS signifies:

(a) MR - Ammeter

(b) H - horizontal

(c) 8 - 8-inch case size

(d) W - White scale

(e) 005 - Zero left, full-scale value of 5.

(f) DC - Direct current

(g) MA - Milliampere

(h) L - internal illumination

(i) S - special scale; as specified (see 6.1)