Tri-Field 50Hz Meter Instruction Manual

ALPHALAB INC. TriField is a registered Trademark of W. B. Lee.


Hold the meter as shown. This prevents your hand from shielding electric fields or microwaves. (Your hand cannot shield magnetic fields.) Read the top scale when the knob is set on "MAGNETIC (0-100 range)", or on "ELECTRIC". This top scale reads 0-100 milligauss when on "MAGNETIC (0-100 range)", or 0-100 kilovolts per meter when on "ELECTRIC". For more sensitivity to weak magnetic fields, set knob on "MAGNETIC (0-3 range)", and read the center scale. When the knob is turned to "RADIO/MICROWAVE", use the bottom scale (.01-1 milliwatt per square centimeter) and point the meter toward the radio/microwave source.

Avoid long term personal exposure to HIGH (red scale) readings in any setting; they pose a possible (but not yet certain) health risk. The dotted red scale is borderline exposure, and probably poses little if any health risk. Below that is generally regarded as safe for continuous exposure.


Switch the knob to "Battery Test". If the battery needs replacement, the needle will be to the left of the line that is itself left of the words "Batt. Test".


The ELECTRIC and RADIO/MICRO-WAVE settings should be low (below the dotted red scale) in most parts of homes or offices, especially if you cup your hand in front of the meter or place the meter in a metal box. In the country, far from power lines, the magnetic field should also read very low (below .2 milligauss).

High Magnetic Field Sources

Hold the meter near these sources, and set the knob on "MAGNETIC (0100 range)." Some of these should read greater than 10 milligauss on the top scale. Your body or hand does not shield these.
  • AC wall adaptors
  • Vacuum cleaner or motorized equipment
  • TV screens
  • Motorized clocks (120 Volt)
  • Lightning
  • Inside of commercial jets
  • Running cars, especially near front floorboard

If you can't get a reading greater than 10, test the battery. (If the battery is bad, the meter needle cannot go up to full scale.)

High Electric Field Sources

Switch the knob to ELECTRIC. If you point the top surface of the meter box (the surface furthest from your hand) toward these sources, some should read greater than 3 kilovolts per meter. (Notice that your body can easily shield electric fields; the reading is lower if you cover the top surface of the meter with your hand. Also, the presence of your hand at the back of the meter compresses the electric field, making it read somewhat higher than if the meter were held in that position hanging by a string.)

  • TV screens
  • Improperly grounded electrical equipment
  • Single "hot" wire, even if insulated
  • Fluorescent lights
  • Electric Blankets, when plugged in, but"off", especially if the AC plug polarity is reversed

High Radio/Microwave Power Sources

Switch to RADIO/MICROWAVE and point the top (front) of the meter toward the following sources. Read the bottom scale. Your hand can shield the higher frequencies (microwave) but not lower frequencies.

Cellular phone*

CB or amateur radio transmitter*

Microwave ovens near door seal. A reading of more than .2 mW/cm2 (needle halfway up) at a distance of six feet suggests a leaking microwave door seal, which should be repaired.

Will also produce electric and magnetic field readings. An ordinary radio phone however, will produce little or no needle deflection.


The battery is a 9-volt rectangular type. The alkaline type will last about 30 hours of continuous use, while the transistor type will last about 10 hours. Turn the meter OFF, unscrew the back (four screws) and slowly separate the back cover. DO NOT PULL APART RAPIDLY - it may break the wires. Disconnect the battery and slide it out by pushing it out from the back. Then replace it. Reconnect the new battery and reassemble. Leave the meter OFF when not in use; even "Battery Test" will draw some power.


The MAGNETIC and ELECTRIC field settings are frequency-weighted from 30 to 500 Hz and are calibrated at 60 Hz. For example, a 60 Hz magnetic field with a strength of 2 milligauss will read "2" on the meter, but 120Hz at 2 milligauss will read "4" on the meter. This is to gauge the currents induced inside the body, which are proportional to field strength multiplied by frequency. From 500Hz to 1000Hz, the response is flat +/-20%. Above 1000 Hz, the
magnetic and electric sensitivities of the meter slowly decrease with increasing frequency, falling to zero near 100 KHz, but with some residual sensitivity up to 100 MHz. In theory, the body's sensitivity to fields should begin to decrease at frequencies above about 500 Hz. Accuracy is +/-20% of scale reading for MAGNETIC, and +/-30% for ELECTRIC (RMS @ 60 Hz).

RADIO/MICROWAVE is sensitive from 50MHz to 3 GHz and is calibrated at home microwave oven frequency (2 GHz). The accuracy is -50% to +100% because of the unpredictable effect of reflections within the room and off the user.


The unit is warranted against defects in materials and assembly for one year from the date of purchase.
Customer should return defective unit, shipping prepaid, for repair or replacement.


Use of the meter is solely at the user's discretion to identify personal exposure to non-ionizing electromagnetism of the strength and types believed (as of May 1992) to pose a possible health risk. Because a meter of this type may malfunction, the user's responsibility is to determine if the meter is working properly by using it to measure a known
reference (see CALIBRATION section of this booklet). Manufacturer or dealer cannot assume responsibility for damages resulting either from a defective meter (except to replace or repair said meter within the warranty period) or from inaccuracies in the present body of knowledge concerning the health hazards of electromagnetism.

The meter should be used so that simple steps (such as moving furniture) can be taken to reduce relative exposure within a home or office. If more drastic actions are contemplated, remember that some readings in the HIGH (red) zone may ultimately prove not to pose a health risk, so consult expert advice before taking more drastic steps, and perform independent tests with another type of meter. Remember that the TriField(r) meter is frequency-weighted, so in most environments, it will read higher in the magnetic field setting than a more traditional meter of the type used in epidemiological studies to set possible hazard thresholds.

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