Feature 1.4-digits display, clear and easy for readings. 2.Mini size, high performance and fast reaction speed. 3.With good stability, high accuracy, anti-interference ability. 4.Using the latest A/D conversion chip, high stability reference IC and stick chip components. 5.It can be applied to voltage and current measurement, also can be an external sensor to measure temperature, pressure, displacement and other physical quantities. 6.Setting parameters will be memorized when power off. 7.Suitable for detecting the speed of every kind of motors. 8.Over-range display: the thousand unit display 1"or -1, the last three do not show. Specification: 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 Measuring range: Speed: 10-9999Rpm Measurement accuracy: 0.1%, reading 1 word. Display mode: 0.56 red, green, blue LED four-digit reading Display refresh rate: