1. DESCRIPTION

The 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 applied to the surface of material of low electrical resistance. In these applications, such as painted metal surfaces, the M1/AC Holiday Detector will locate these points very accurately with an audible bell signal. This method of electrical inspection of thin film is considered a non-destructive test with an applied voltage of 67-1/2 Volts D.C. to the coated surface.
 
 

2. DESIGN AND CONSTRUCTION

The detector operates for 110/120 volt 50/60 cycle A.C. line current and the electrical design of the M1/AC Holiday Detector utilizes a sensitive relay which is activated by a voltage regulated, solid state power supply. When a current of approximately 750 microamperes flows through the system the relay closes and actuates the signal bell.

The electrical components are housed in an anodized aluminum case for maximum protection and the detector is equipped with on/off switch, pilot light, wand terminal, ground terminal, fuse receptacle, A.C. cord and signal bell.

The exploring electrode consists of cellulose sponge attached by the metal clamp to a phenolic wand handle and wand cable. The ground cable consists of a cable with direct connect clamp.
 
 

3. OPERATION

Attach the electrode clamps to the end of the WAND, dampen the SPONGE ELECTRODE and place it between the clamps and tighten the clamps with the screw until they are well down in the SPONGE ELECTRODE. Attach the ground wire (lead with battery clamp) and the WAND to the appropriate terminals, clip the ground wire to some point where the metal surface is bare. Plug the A.C. cord into an A.C. outlet and turn the instrument ON. Now touch the dampened electrode to a second point where the surface is bare and note that the bell will ring. The electrical operation can also be checked by touching the electrode to the ground wire terminal.

The detector is now ready to operate by passing the damp sponge over the painted surface. When holiday is picked up by the bell alarm, the ELECTRODE can be turned on end and the exact spot of failure can be noted by searching with the tip or corner of the ELECTRODE.

Some operators have found that the M1/AC Holiday Detector is effective on films to 20 mills IF a wetting agent is used with water. Wetting agents similar to those used in developing photographic film are satisfactory.

If inspection of paint film is to be made which lies on concrete, the ground wire must be attached to a metal structure which is imbedded in the concrete as a pipe or a reinforcing rod.
 
 

4. ADJUSTMENT OF BELL SIGNAL

The sensitivity of the bell is determined by the setting of the sensitive relay. This relay can be adjusted by removing the top of the instrument case which exposes the relay and bell. Turning the adjusting screw (on top) clockwise REDUCES the sensitivity of turning the adjusting screw counter-clockwise INCREASES the sensitivity. The factory setting for sensitivity is made by having the relay just close when a 100,000 ohm resistor is placed across the terminals. By using various size 1/4 watt resistor as standards, the sensitivity can be reset to any predetermined value in this manner. The factory setting allows sufficient sensitivity for the detector to be used on coated concrete as well as on coated metal surfaces. Keep the detector case dry and when the detector is not in use, remove and dampen the sponge and allow it to dry without the clamps and it will return to its original shape.
 
 

5. SHIPPING INSTRUCTIONS 

All instruments being returned for repair should be sent PREPAID to either address below: 

Tinker & Rasor
417 Agostino Road
P.O. Box 281
San Gabriel, CA 91778