Should the perfect state of the sampling detector be a wall with uniform density?But in reality,there is no wall with uniform density in daily life,it is even possible that the density change is relatively large,this can cause false detector alarm,so users must repeatedly and detection in the detected area.First start sampling from a large range of which is safe to uniform region Then gradually narrow the detection range until the density anomaly (DE) is found Users should not release the test button during the entire sampling and detection process this is a key step in the operation How to judge the quality and sensitivity of the detector?Pull out the function switch detector The detector by the left hand and sampling the air density in front of the detector;after a Di-Di sampling sound is finished Hold the left thumb pressing the button on the palm of the right hand slowly close to The detector At this time you will find the bar graph gradually from two sides of the Center;Detector also makes warning sound When it takes palm to detect detector region it is back to normal.This procedure can be used to test whether the function is feasible under simple condition Power supply: 1 x 9V 9V 6F22 battery(without battery) Detection depth: 19mm; Position accuracy: 3mm colour: black-yellow Material: ABS size: 145x62x25mm Package Contents: 1 x TS78B Detector Only the above package content, other products are not included. Note: Light shooting 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.