Features Good performance: digital LED speed meter adopts the latest A/D conversion chip and high stability benchmark IC, adopts electronic chip component, reasonable circuit design. Input pulse signal: NPN/PNP open collector, contact c holder, contactless switch, level pulse. Input signal voltage: low level: -30V-0.6V, high level: 4-30V. Practical Measuring Tool This speedometer can be used to measure voltage, current and external sensors to measure temperature, pressure, displacement and other physical quantities. Suitable for all types of digital instrument displays. Easy Installation The external appearance adopts the standard size and is convenient to install. Good stability, high precision and strong anti-interference ability. Measuring range: Frequency: 9999Hz, 999.9HZ, 99.99K HZ, automatic switch selection. Specifications: Measuring accuracy: ±0.1%. Display mode: 0.56 inch LED. Display refresh rate: >3 times/sec. Working Power Supply: DC8-24V 30mA Measuring Range: 10-9999RPM Hall proximity switch: magnetic Appearance size: 80 x 42 x 25 mm/3.14 x 1.65 x 0.98 inches. LED indicator (optional): red, blue. Weight: 80g (red), 105g (blue) Exceeding range indicator: the first shows "1" or "-1", the last three does not Precautions: 1. Connect the plug correctly according to the wiring diagram. 2. Strong electromagnetic interference should be avoided and it is better to use shielded wires or double stranded wires to measure conductors 3. The counting signal of the counter and the switches of the zero erase signal input or circuit must be as close as possible to the terminal of the counter to make the signal line as short as possible 4. Avoid others such as: high voltage cables or power cables etc. with the same hose or twisted track line to avoid unnecessary interference terminals count 5. It is not recommended to use a mechanical switch or micro switch, as they have a relatively short service life and can be accidentally counted after a long time. If you use a mechanical switch or micro switch, please try to use a better quality so as not to count, and strongly recommend a magnetic control switch Package includes: 1 x tachometer. 1 x Hall NPN Proximity Sensor Package List