MILLIVOLT DROP TEST

The millivolt drop test is generally associated with

testing for weld quality on the armature. It is the

best test for verifying armature weld quality.

The millivolt drop test is the ultimate electrical test

for detecting bad welds. Unfortunately, it is

difficult to make on armatures with large diameter

wire and nearly impossible to make on armatures

with small wires.

The difficulty is breaking through the insulation on

the wire as it exits the tang or commutator bar

contact. The one testing contact, usually a sharp

knife edged probe, from the KOM (Kelvin Ohm

Meter) can cut through small wires and destroy

the armature. Contact with the knife-edge probe

needs to be made on each bar. Since this is such

a difficult test to perform, it is only practical as a

laboratory test.

Various test methods have been developed over

the last twenty years that come close to making

this test. These tests make it possible to test

100% of the armatures. However, none of these

tests are as accurate or repeatable as the Millivolt

Drop Test.

ESW's weld test, which uses techniques that have

been developed over the past 20 years, comes

very close to the Millivolt Drop Test. The

repeatability and speed of the test using a

stationary armature test fixture assures that a

reliable test has been performed.