Features [Performance Advantages]: Good stability, high precision, strong anti-interference ability [Easy to Install]: The appearance adopts standard size, easy to install [Input Pulse Signal]: NPN/PNP open collector, contact switch, non-contact switch, level pulse [Input Signal Voltage]: Low level: -30V -0.6V, high level: 4-30V [Measurement Range]: Frequency includes 9999Hz, 999.9HZ, 99.99KHZ, automatic switching selection Features: 1、Good stability, high precision and strong anti-interference ability. 2、The external appearance adopts standard size and convenient  to install. 3、Input pulse signal: NPN/PNP open collector ,contact switch, contactless switch, level pulse. 4、Input signal voltage: low level: -30V -0.6 V, high level: 4-30V. 5、Measuring range: frequency: 9999Hz, 999.9 HZ, 99.99 KHZ, automatic switching selection. Specifications: Measurement accuracy: ±0.1% Display mode: 0.56"LED Display refresh rate: >3 times/sec Working power supply: DC8-24V, 30mA Measurement range: 10-9999RPM Hall proximity switch : magnetic Appearance size: 80 x 42 x 25mm/3.14 x 1.65 x 0.98inch LED display(Optional): red, blue Weight: 80g(red),105g(blue) Overrange display: the first one shows "1" or "-1", and the latter three do not show Precautions: 1. Connect the plug correctly according to the wiring diagram 2. Should avoid strong electromagnetic interference and it is better to use shielded wire or double stranded wire for measuring conductors 3. The counting signal of the counter and the switch of the zero clearing signal input or the circuit shall be as close as possible to the terminal of the counter to make the signal line as short as possible 4. Avoid with other such as: high voltage wires or power wires and so on with same tube or twisted  trace line, in order to avoid unnecessary interference.If necessary, please use the shielded wire, shielding layer connect the"+" of the count terminals 5. It is not recommended to use a mechanical switch or micro switch because they have a relatively short life span and can be counted by mistake after long time. Package Included: 1 x Tachometer 1 x Hall NPN proximity sensor Package List