The Hall switch is NPN normally open, and the detection distance of the Hall switch needs to be within 10MM. The installation diameter of the Hall switch is 12MM, and the wire length is within 1 meter. Strong electromagnetic interference should be avoided, and the measurement wire is to use shielded wire or twisted pair. The counting signal of the counter and the switch or circuit of the clear signal input should be as close as possible to the terminal of the counter, and the signal line should be as short as possible. Avoid the same tube or twisted wiring with other such as strong current wires or power wires to avoid unnecessary interference. If necessary, please use shielded wires and connect the shielding layer to the counting terminal "+". It is not recommended Use mechanical switches or micro-switches, because their life is relatively short, and they are easy to miscount after a long time; for example, when using mechanical switches or micro-switches, please try to use better quality to avoid miscounting. It is strongly recommended to use magnetic control switch. Working power supply: DC8-24V, 30mA Display mode: 0.56 red LED, four-digit reading Measuring range: 10-9999 Measurement accuracy: +/- 0.1%, reading +/- 1 word Display refresh rate: more than 3 times/sec Over-range display: the first digit displays "1" or "-1", the last three digits do not display Colour: as shown Material: ABS Package Contents: 1 set * Red tachometer Only 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.