Review for: Extech 480826 EMF Meter (30Hz to 300Hz Triple-Axis) OVERVIEW: ----------- Measures EMF strength of low frequency (30Hz-300Hz in this case) portion of AC MAGNETIC FIELD (NOT AC electric field, too) from any one of 3 directions in milligauss (mG) or microteslas (uT). This is NOT giving you a single value calculated from separate readings but rather 3 separate readings from each of 3 directions. It has a hold button to freeze a reading. Because cell phones and microwaves are in a much higher frequency range, this product does not measure EMF (RF) at those frequencies. You would want a separate meter for that. The 3-axis Thor's hammer like sensor may at first seem of questionable value, but it does add some convenience. The Achilles Heal of this instrument, and the reason this is 2 stars and not 4 or 5, is that according to Extech Sales and Engineering, and confirmed with them as well, this model is HIGHLY INACCURATE for LOW EMF readings .. a fixed +/- 8.3 milligauss. This would mean a reading of 2 milligauss is actually 2 +/-8.3 milligauss. This is because the 4% accuracy is not of the displayed value but rather of the the value of the end of the measurement range (200 milligauss x 4%). Since so much of the consumer use of EMF checking is in the single and low teens mG, this is unfortunate. To their credit Extech is up front about this unit being mostly for noting the existence of stronger EMF at low frequencies, not necessarily for quantifying it. MAIN VALUES: -------------- - Measures EMF at 30Hz-300Hz low frequency range, which covers most EMF generated by AC power in most homes/offices. 60Hz (U.S.) and much of the EMF generated by resulting harmonic frequencies .. 120Hz (2nd harmonic), 180Hz (3rd), 240Hz (4th), 300Hz (5th). - Triple Axis measurement, however, again there is NOT the option of a single value calculated from 3 separate readings but rather 3 SEPARATE AXIS EMF READINGS. - Has a HOLD BUTTON to freeze the display value. - The wand on occasion can be handy, for example reading the display while extending the wand towards ceiling bulbs. CONS: ------ - According to, and confirmed with Extech Sales and Engineering, the accuracy is HIGHLY INACCURATE for LOW EMF readings .. a fixed +/- 8.3 milligauss (mG). Since most suggested defensive limits for extended exposure are 1mG-2mG or so, this greatly limits its utility. See paragraph above under "The Achilles Heal of this instrument.." for more detail. - Measures only AC magnetic field (mG/uT), not AC electric field (V/m,mW/cm2, etc.). Adding electric field measurement with decent accuracy would have added greatly to the cost. NOTES: ------- - Like other meters anywhere near this price range, the company doesn't claim this unit will filter out 300MHz EMF as well as academic/professional units like the Enertech Emdex II filter out EMF from outside its measurement range. - This frequency range does not cover cell phones or cordless phone signals, microwave oven radiation, or other high frequencies often referred to as RF (radio frequency). SAMPLE EMF MEASUREMENTS: ----------------------------- There is no definitive consensus nor clear epidemiological evidence yet as to how much milligauss (mG) for extended periods could be harmful (within reasonable home/office real world levels). However, there is a consensus from studies that staying under 1mG-4mG would be a good defensive strategy in case 20-40 years from now longer term studies (think smoking, etc.) start showing stronger causal relationships. Most folks who care about this aim for under 2mG, preferably under 1mG, especially where pacemakers can be involved. Here are some sample readings of LOW frequency AC MAGNETIC field EMF (Note: not electric field): (1) Alarm Clock 3" 25mG 6" 10mG 1' 3mG 1.5' 1.8mG 2' 0.5mG (2) Microwave Oven #1 (Home) Towards decent seal: 6" 10-30mG 1' 4-25mG 2' 1.5-5mG Towards questionable seal: 6" 160mG 1' 45mG 2' 15mG (3) Microwave Oven #2 (Office) 6" 50mG 1' 20mG 2' 3mG 3' 1.2mG (4) CRT Television (20" Sony WEGA) Down the middle: 6" 0.9mG 1' 0.5mG 2' 0.2mG Corners: 6" 5.5mG 1' 3mG 2' 0.7mG Sides/Edges in the middle vertically: 6" 7mG 1' 3.5mG 2' 0.9mG (5) 2012 LED Television 3" 0.6mG (6) Dehumidifier (Large 70pt. Frigidaire) Around most of it: 1" 0.5mG On one side we get: 3" 4.3mG 6" 1.4mG 1' 0.6mG 2' 0.3mG (7) High-End Modern Very Large Copy Machine Not much mG at all (8) Office Ceiling Fluorescent Bulbs 6" 50mG 1' 20mG 2' 3mG 3' 1mG (9) Uncovered CFL Bulb 3" 3mG 6" 0.5mG (10) Box Fan 6" 6mG (from center motor only) 1' 1mG (11) Standing child's fan 6" 6mG 1' 1.2mG 18" 0.6mG (12) Washer (Clothes) Top: 1" 15mG 6" 0.5mG-1.5mG Bottom - Usually: 6" 0.9mG-1.5mG Bottom - while Spinning: 3" 35mG 6" 22mG 2' 4.5mG 3' 1.9mG 4' 1.3mG (13) Dryer (Clothes) Top: 6" 0.5mG Bottom: 6" 1.5mG (14) Dishwasher Top: 6" 2mG 1' 1.5mG 2' 0.7mG Bottom: 6" 12mG 1' 5mG 2' 1.8mG (15) Automobile Moving car: Head height Lap 2.2mG Stopped car: Head height 0.5mG Lap 1.4mG WHICH DIRECTION IS X, Y, Z AXES: ---------------------------------- X - Holding the sensor up with the graphic facing you, X-axis points to the right side of the sensor. Y - Straight out the top of the sensor unit, along the line of the hand grip. Z - Holding the sensor up with the graphic facing you, Z-axis points away from you on the other side from the graphic. EMF METER SHOPPING GENERAL NOTES: -------------------------------------- EMF FROM LOWER FREQUENCIES: At LOWER FREQUENCIES we can measure magnetic fields (in milligauss (mG) or microteslas (uT)), and higher end units also measure electric fields (V/m,W/cm2, etc.). Unlike higher frequencies where magnetic and electric fields are strongly coupled together, at lower frequencies you measure them separately. As noted elsewhere in the review, for biological exposure it is suggested to play defense and keep prolonged exposure from lower frequency Magnetic Fields to under 1-4 mG (preferably under 1-2 mG) but there is no definitive consensus as to the long term biological dangers, and where the safety lines are. Regarding Electric Fields of 50-60Hz (AC Power), there is some rough consensus out there to keep below 10-20 V/m and sleep at a spot below 5 V/m, though again opinions vary. 5 V/m was the recommendation in Germany and by the IRPA/INIRC for "private individuals", 10 V/m for "workers", with 25 V/m for "workers" for max. 2 hours. ACGIH recommend 1 V/m for those with pacemakers or other electrically sensitive implants. The fields in the lower frequency ranges are sometimes referred to as ELF (see chart below for usual acronym meanings of this sort), or even confusingly as EMF which is also often used to define such fields at most frequencies. EMF(RF) FROM HIGHER FREQUENCIES: At HIGH FREQUENCIES like those the high frequency meters measure, the magnetic and electric fields are coupled so strongly together that it is one field that is measured, usually in V/m or mW/cm2, etc. For microwave ovens (2.45 GHz) biological exposure is often recommended to not exceed 5 mW/cm2 (milliwatts per cm squared), however again opinions vary. Some school or hospital exposure limits for 300MHz-300GHz: - France, Italy 10 mW/cm2 in schools - Switzerland 9.5 mW/cm2 in schools, 4.25 mW/cm2 in hospitals - Belgium, Luxembourg 2.4 mW/cm2 For RF Fields of 900MHz, exposure limit recommendations around the world appear to range from .001W/m2 to 4.5W/m2, the latter being in Germany and the ICNIRP recommendation in '98. For RF Fields of 1800MHz, exposure limit recommendations around the world appear to range from .001W/m2 to 9W/m2, the latter being in Germany and the ICNIRP recommendation in '98. The higher frequencies are often referred to as RF (radio frequency) frequencies (think cell phones, microwaves, etc.) and thus you'll see some meters with "RF" in the title or description. MAGNETIC VS. ELECTRIC FIELD MEASUREMENT: AC MAGNETIC FIELDS are much harder to shield than electric fields. On the ot
