Author: R. Teliczan
Edition: Model Aviation - 1983/04
Page Numbers: 74

Home Grown Plug Analyzer

By Ray Teliczan

Got an old transmitter RF meter lying around just getting in the way? Use the meter for this simple device and learn a lot about the condition of your glow plug as an aid in engine starting.

Materials Needed

  • 4 ft. of No. 14 extension cord
  • One pair of alligator clips with boots
  • Two solder lugs
  • One Ace SPST switch
  • One old transmitter RF panel meter
  • A battery to light the glow plug
  • Electrical tape, cyanoacrylate (CyA) glue

Preparation

  1. Extension cord:
  • On one end, shorten one conductor to about 1½ to 2 in. Install the boots and solder on the alligator clips.
  • On the other end, shorten one conductor by 8 in.; save this 8-in. scrap.
  1. Panel meter:
  • Remove all of the fine copper windings from the rear of the meter.

Assembly

  1. Take the single 8-in. conductor (the shortened end) and wrap it one turn around the meter where the fine copper winding was removed. Secure this one turn with tape or CyA glue.
  2. Glue the switch to the top of the meter with CyA.
  3. Wire the switch so that it opens both conductors (both lines are broken by the switch).
  4. Use solder lugs on the battery terminals for solid connections.
  5. Use the 8-in. scrap to connect the switch to the battery.
  6. Connect the battery leads and extension cord leads to the switch lugs so the switch interrupts the circuit between the battery and the clips.
  7. Before permanently gluing the meter/switch assembly to the battery, check meter deflection by attaching a glow plug to the alligator clips:
  • If the meter deflects in the wrong direction, reverse the battery leads or wrap the single turn of wire on the meter in the opposite direction.
  1. Glue the meter to the battery with CyA, then wrap the assembly with electrical tape to insulate the switch terminals.
  2. Add a second wrap of tape further down the battery to act as a strain relief.

Operation / Testing

  • A normal glow plug will produce a meter reading of about 0.5 (meter units).
  • A flooded plug or one whose element is against the plug shell will read considerably higher.
  • A blown plug will read 0 (no deflection) — as will the meter when the switch is turned off.

Transcribed from original scans by AI. Minor OCR errors may remain.