Trifield Gauss Meter
Depending on where the knob is set, the meter detects either frequency- weighted magnetic fields (two separate scales), or frequency-weighted electric fields in the ELF and VLF range. It has significant sensitivity at 100,000 Hz, well past the 17,000 Hz horizontal scan of video displays. The radio/microwave setting can detect up to three billion Hz (3 GHz), which lets you gauge radio- wave power, CB and cellular phone equipment, and many types of radars.
This meter is the only one which combines magnetic, electric, and radio/microwave detectors in one package, so that the entire nonionizing electromagnetic spectrum is covered. In addition, the magnetic setting and the electric setting measure true magnitude, a feature found elsewhere only in more expensive meters. If you hold the meter in the center of a room and tip it to various angles, the magnetic reading will stay approximately the same regardless of which way you tip or rotate it. The electric reading is similar, although the presence of your body alters the actual electric field, so readings will vary more. The radio/microwave setting reads the full power of radiowaves when the meter is pointed toward the source.
Surprisingly, the standard TriField Meter is one of the least expensive meters available. The few other meters below $200 read only low-frequency magnetic fields and only in one direction (not true magnitude). The magnetic section of the TriField meter has three field-detecting coils pointing in the X, Y, and Z directions. A circuit amplifies these signals and gives them the proper frequency-weighting (sensitivity increases linearly from 30 Hz to 500 Hz, but with some residual sensitivity up to 100 kHz). A unique network combines the three coil outputs nonlinearly to approximate a true magnitude. The meter is sensitive from 0.2 to 100 milligauss full scale at 60 Hz (or 0.1 to 50 milligauss full scale at 120 Hz, etc.) with a resolution of 0.2 milligauss in the sensitive range. Accuracy is +/-20% at mid-range. A version with flat frequency response (instead of linear sensitivity increase) is also available for the same price.
The TriField Meter comes with a 9-volt transistor battery included. This type of battery lasts about 10 hours (total measurement time). When the BATTERY TEST reads low, the battery can be replaced with any rectangular 9 volt transistor or alkaline (which lasts about 50 hours) type. This meter is manufactured in the USA. TriField is a registered trademark of W.B. Lee.