Features Good stability, high precision and strong anti-interference ability.It has been rigorously tested to meet standards. The external appearance adopts standard size and convenient to install. Input pulse signal: NPN/PNP open collector ,contact switch, contactless switch, level pulse. Input signal voltage: low level: -30V -0.6 V, high level: 4-30V.Measuring range: frequency: 9999Hz, 999.9 HZ, 99.99 KHZ, automatic switching selection. We want to bring you the best product experience. If you have any pre-sale or post-sale questions, please feel free to contact us. We are committed to bringing our customers the best shopping experience and will solve your problems in a timely manner. Descriptions: Digital LED tachometer adopts the latest A/D conversion chip and the high stability benchmark IC, adopts electronic chip component, reasonable circuit design. It can be applied to the measurement of voltage, current and external sensor to measure temperature, pressure, displacement and other physical quantities. Suitable for all kinds of digital instrument display. 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 Package Included: 1 x Tachometer 1 x Hall NPN proximity sensor Package List