The Tinker & Rasor Model M1/AC Holiday Detector is a highly sensitive electrical instrument, designed to locate holidays (pin holes, voids, etc.) in thin film coatings of relatively high electrical resistance when such films are brushed or sprayed to the surface of material of low electrical resistance. In these applications, such as painted metal surfaces, the M1/AC Detector will locate these points very accurately. This method of electrical inspection of thin film is considered a non-destructive test with an applied voltage of 67.5 volts DC to the coated surface.
The Model M1/AC 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 M1/AC 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 110/120 VAC, 56/60 Hz line current, and the electrical design of the M1/AC 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.