Installation and operation - Mounting: Designed for a mounting hole 85 mm in diameter and 70 mm in depth; insert the gauge into the hole and fasten securely. - Adjustment: Speed ratio adjustable from 1 to 300; use the back button to set. Idle speed is typically 600–800 rpm. See the owner manual for full details. Compatibility and signals - Engine types: Suitable for diesel engines and gasoline engines. - Signal sources: Tachometer can receive signals from the engine, ignition coil, or crankshaft sensor. Display and logging - Readouts: Displays rpm and running hours. - Hourmeter: Hourmeter cannot be reset. Power, protection, and reliability - Lighting and voltage: Red backlight; operates on 9–32 V DC (12 VDC / 24 VDC recommended). - Protection: 100% waterproof and anti-fog protection. Use scenarios - Diesel generator or industrial machinery: Install to monitor engine RPM and track running hours during maintenance cycles. - Gasoline engine applications: Use on cars, small boats, or equipment to observe RPM and engine hours for service planning. - Field or construction equipment: Mount in tractors or off-road machines to ensure correct engine operating range and to log hours for servicing. This description preserves the original specs and functions while presenting a clear, customer-friendly overview.