Holiday Detector (In-Plant:

The Model M1AC Detector is designed to inspect thin film coatings from 1 to 10 mil using ordinary tap water. The cellulose sponge electrode, when dampened with water is moved over the coated surface. When the electrode passes a void or bare spot a small current flows and actuates an audible signal. The M1AC Detector is effective on films to 20 mils if a wetting agent is used with the water. Non-sudsing type wetting agents similar to those used in developing photographic film are recommended.
The detector operates from 110120 VAC, 5660 Hz line current, and the electrical design of the M1AC Detector utilizes a very sensitive relay which is activated by a voltage regulated, solid state power supply. When a current of approximately 750 microamps flows through the system, the relay closes and actuates a signal bell.