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Tech Data
Tech Data
Parts List
Parts List
Model M1 AC Holiday Detector


For use such as: Coatings, in-plant environments, rebar, pipelines, sheet materials coated with thin film under 20milsa,

Model: M1-AC Low Voltage Holiday Detector


  • Use on thin film coatings on conductive substrates such as tanks, concrete, etc.


  • Recommended Annually


  • 67.5v D.C. Output

  • 80 ohms* Resistance for coatings on metal

  • 90 ohms Resistance for coatings on concrete

  • (Factory setting is 80 ohms. See Instructions for information on changing setting to 90 ohms)


  • 5.75" x 12.25" x 10", 10 lbs. (146mm x 311mm x 254mm, 4.5kg)-Instrument

  • 14" x 12" x 6", 12 lbs. (355.6mm x 304.8mm x 15.24mm, 5.44kg)-Shipping

Model: M1-AC Low Voltage Holiday Detector

The same features found in our Model M-1 are also found in the Model M1-AC. The M1-AC is powered by 115 or 230 volt, 60 Hz, A.C. and produces a regulated output voltage of 67.5 volts D.C. This allows for 24 hour "in-plant" operation without down time for battery changes. The M1-AC is used extensively in re-bar coating  and other production type coating plants.

As with all Tinker & Rasor equipment the Model M1-AC is rugged, reliable and ready for work right out off the box.

Model: M1-AC Low Voltage Holiday Detector

1. Description:

The Model M1/AC Holiday Detector is a highly sensitive electrical instrument, designed to locate holidays (pinholes, 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 approximately750 microamperes flows through the system the relay closes and actuates the signal bell.

The electrical components are housed in a plastic, waterproof case for maximum protection and the detector is equipped with on/off switch, LED light, wand, ground wire, fuse receptacle, A.C. cord and signal bell.

The exploring electrode is open-cell sponge material and is conductive when saturated with a wetting solution. The sponge electrode is attached to the non-conductive wand handle by means of the bolt with knob, plastic sponge holder, and backing plate. Dampen the SPONGE ELECTRODE.


3. Operation:

NOTE: The SPONGE ELECTRODE is shipped in a compressed state. It will expand when wet.

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 (110v) 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 a 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 embedded in the concrete, such as a pipe or a reinforcing rod.

4. Adjustment Bell of 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: 


Ship Via Courrier (UPS, FedEx, DHL, etc)

Tinker & Rasor

ATTN: Repairs

791 S. Waterman Ave.

San Bernardino, CA 92408


Ship Via US Postal Mail

Tinker & Rasor

ATTN: Repairs

PO BOX 6890

San Bernardino, CA 92412-6890

Include with shipment information the nature of the problem, purchase order, serial number

and return delivery address, phone and fax numbers. Immediate service is guaranteed!

Model: M1-AC Low Voltage Holiday Detector

 Replacement Parts Available:

  • #085-033 M1/AC Instrument - US$1225.00

  • M/1 WAND – includes wand, cable, sponge, sponge holder, sponge backing plate, sponge holder knob - US$60.00

  • 177-071 Wand 18" w/ Red Cable- US$50.00

  • 055-882 Electrode, Sponge, 6" x 3.5" x 2" - US$5.00

  • 076-050 Sponge Holder - US$3.50

  • 094-030 Sponge Holder Knob - US$3.80

  • 014-195 Sponge Backing Plate - US$1.00

  • 010-002 Batteries, AA, (6) - US$10.62

Model: M1-AC Low Voltage Holiday Detector


Low Voltage (Wet Sponge) Holiday Detector

US $1225.00


  • Regulated 67.5v output

  • Push button calibration check

  • 2 Resistance settings

  • (80K Ω Metallic sun straights)

  • (90K Ω for coatings on concrete)

  • Typical under 20mils

  • Non-Destructive

  • Mil-Spec Case

Included with the M1-AC:

  • Instrument with AC power cord

  • 15’ Ground Cable

  • 18" wand with 6' cable

  • Sponge electrode 6" x 3.5" x 2" (Sponge shipped compressed)

  • 4 oz. Bottle of "Water Wetter"

  • Instructions Included

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