This meter reads the component of magnetic fields in the direction of the cable. The sensor is the square bulge at the gray tip of the cable. The sensitive region is the center of that bulge. The direction of sensitivity is parallel to the surface of the bulge, in a direction parallel to the cable. On the display, the numerals to the left of the decimal point are in milligauss, which is to say in units of 1/1000 gauss. (One gauss is the same as one oersted). The Earth field is approximately 500 milligauss, and is not purely horizontal except in a few areas of the Earth. (In North America, the north field is declined from horizontal north, and it reads negative on this meter. To find that direction, set the MILLIGAUSS RANGE knob to 1999.9, and point the tip of the cable north and then tip it slowly downward and slightly left and right until you find the direction with the largest negative number. In Asia, the north field is generally close to horizontal).

Three OFFSET knobs allow you to add or subtract up to 600 milligauss. This is useful if you are using the 199.99 range in a high field (over 200 milligauss). When you set a certain amount of offset, it is exactly the same amount in the 1999.9 and 199.99 ranges. For zero offset, set all three knobs to zero. This meter is usually used with all three offset knobs turned to zero, and the MILLIGAUSS RANGE set at 1999.9. Then the meter reads the actual magnetic field up to +/- 1999.9 gauss, and you point the end of the sensor in the same direction as the component of the magnetic field that is being measured.

“Low Battery” will show on the display when approximately 10 minutes of battery life remain. Slide off the back panel to replace the single 9-volt battery. An external power input jack is on the meter. When you plug in a 2.1mm DC power plug, it will override the battery. The external power should be between 10 and 15VDC, at least 50ma, center positive. (If you accidentally use wrong polarity, it will not damage the meter). An AC adaptor is not supplied, except in North America.

This meter reads DC magnetic field with accuracy of +/-0.5% of the reading in the temperature range 30 ° F – 110 ° F. With all three offset controls set to zero, when the meter reads zero, then the field is between + 0.5 and –0.5 milligauss. Range is + to – 1999.9 milligauss. It is warrantied for one year and was manufactured by AlphaLab, Inc. in the USA (tel: 1-801-487-9492). See www.trifield.com.