Figure 4-18. Blasting galvanometer

TM 9-1300-277

to activate the generator, and two binding posts for

attachment of firing leads. The test set is waterproof

and may be used at temperatures as low as -400 .

Continuity testing is accomplished by connecting the

firing circuit to the test set binding posts and then

depressing the handle sharply. If there is a cont 1uous

(intact) circuit (even one created by a short), the

indicator lamp will flash.

b. Blasting Machines (fig.

4-20).

Blasting

machines are used to provide the electric impulse

needed in electrical detonations. There are six models

which derive their power directly from a shunt-: wound

generator and two models, the M32 and M34 which

derives their power from an alternator and use a

capacitor discharge output circuit. The term used in

many NATO countries for "blasting machine" is

"exploder" or "dynamo exploder." The generator type

machines are all actuated by means of a gear-driven

armature. The 10-cap machines have metal cases and

twist-type drive handles. The higher capacity (30, 50,

and 100 cap) machines have varnished or painted wood

cases and plunger-type handles. The machines most

often used are the 10-cap and 50-cap machines.

(1) Newer machines (10 cap and 50 cap). In

addition to having significantly higher electrical output

than their predecessors, these machines include a built-

in safety circuit. This circuit allows no current to reach

Figure 4-18. Blasting galvanometer.

the terminals until the machine's handle (or plunger) has

been actuated with sufficient energy to gain nearly the

maximum output from the machine.

(2) Older machines (10 cap, 30 cap, 50 cap,

and 100 cap ). These include a switch which delays the

flow of current from the generator to the output

terminals until the handle (or plunger) is near the end of

its travel. This switch assures that the output produced

by the machine's mechanism does not reach the

terminals until the operator is producing maximum

force.

(3) Blasting machine: M32. This small, light-

weight blasting machine is intended to replace the

larger, heavier machines. Instead of a shunt-wound

generator, this machine uses a small alternator which is

gear-driven by the handle-actuated plunger.

The

electrical output

Figure 4-19. M51 blasting cap test set.

4-15