The EMF Meter is a compact and easy to use Magnetic Field strength meter. The EMF Meter can be used indoors or outdoors for measuring any electric device or power lines. There are 5 LED's, each represents a field strength range.OPERATION: 1. Hold the EMF METER with your thumb on the switch; 2. Point it toward the EMF source, then depress and hold down the switch (a short flash of the LED's will occur); 3. The LED will indicate the range of the EMF at that level; 4. Moving the device from side to side or rotating it may change the reading; the highest reading is most accurate; 5. Move closer or further to the EMF source to determine the "Normal" zone, as indicated by the Green LEDHelptul Hints: Record the readings on the enclosed Exposure Log, repeat periodically, since fields can change in strength; If the GREEN LED (Normal) doesn't light, the battery is low; To change battery remove the two screws, replace 9V batterySPECIFICATIONS:Detection Range: 0 to 20+ milliGaussDetection Frequency: 50/60 Hz (50 to 1000 Hz-ELF) (1000 to 20,000 Hz-VLF)Accuracy: 5% (typical)Operating Temperature: 0 to 120 (-18 to 49)Battery Requirements: 9 Volt batterycolour: blackMaterial: plasticSize: 14.3 cm x 2.2 cm x 5.3 cmPackage Contents:1 x EMF Gauss Meter (with Battery)1 x English manualOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.