Household digital display electronic air detection negative oxygen ion tester         OOTDTY            Air Negative Ion Measuring Instrument Tester Ion Meter Aeroanion Detector Negative Oxygen Ions Anion Concentration Detector Auto Air Purifier     Features:     This negative ion tester can only measure some household appliances with negative ion generator, such as negative ion air purifier, air conditioning fan, air conditioner, etc. which can release more than tens of thousands of high concentration negative oxygen ions. It can not test negative ions released from some ordinary natural environment and some solid ions.     The tester is easy to carry and is suitable for testing high concentration ion sources such as various positive and negative ion generators, air purifiers and air conditioners. Measurement range: 10,000-19,990,000 (ion/cm³)          Usage method:     1. Turn the switch to ON gear     2. Keep the thumb in contact with the square metal sheet of the front panel. The metal sheet on the back faces the air negative ion generator to be tested. The closer the distance between the thumb and the air negative ion generator to be tested, the higher the degree of the tester, and vice versa, the smaller the degree of the tester. Therefore, in order to ensure the accuracy of the measurement results, please keep the tester at an appropriate distance from the air negative ion generator to be tested.     3.Do not-touch the square metal sheet on the back of the tester with your hands during the measurement. Otherwise, the degree will be inaccurate.     4. There is no sign in front of the degree shown. Indicates that positive ions are measured; if "-" is displayed, negative ions are expressed.     5. Keep the machine switch in "off" position before each measurement.          Specifications:     Shell Material: Plastics     Size: 80*30*10mm/3.15*1.18*0.39"     Weight: 91g          Notes:     1. Due to the different monitor and light effect, the actual color of the item might be slightly different from the color showed on the pictures. Thank you      2. Please allow slight measuring deviation due to manual measurement.           Packages:      1 X Negative Ion Meter