What is the installation and setup process of the tachometer?
Installing a speed indicator that reads the shaft correctly
A reliable tachometer installation needs suitable mounting, a clean sensor signal and the correct speed scaling. A handheld instrument mainly requires measurement preparation; a fixed panel tachometer also needs power, sensor wiring and output configuration. Terminal assignments, wire colours and panel dimensions are model-specific.
1. Identify the instrument and signal requirements
Use the complete model code to establish the supply rating, supported sensor inputs, speed range and output type. Before wiring or fitting targets, isolate energy sources, verify the absence of voltage and prevent unexpected shaft movement. Mains wiring requires competent electrical personnel.
2. Mount the indicator and sensing hardware
For a panel-mounted indicator, follow the dimensional drawing for cutout size, panel thickness and rear clearance. Fit the retaining hardware and gasket correctly and use the specified tightening torque. An enclosure protection rating may apply only to the front face; do not assume the rear terminals provide the same IP protection.
For handheld optical measurement, clean the target and attach the specified reflective mark while the shaft is stopped. A one-pulse-per-revolution setup needs one mark; unwanted reflections can introduce extra pulses. Follow the instrument's alignment and distance requirements. For contact measurement, secure the correct adapter and tip; slipping or misalignment introduces error.
Use a rigid bracket for a fixed sensor. Match the metal target to the inductive sensor, the optical target to the photoelectric sensor, or the magnetic target to the Hall sensor. With an encoder, check coupling alignment and permitted shaft loads. The sensing clearance must remain suitable throughout the complete revolution, without target contact.
3. Match the electrical interface
The NPN or PNP output must match the instrument's selected input mode. Connect power, sensor output and signal reference using the manufacturer's wiring diagram. A common-referenced input and an isolated or differential input do not necessarily use the same connections. Check the sensor supply current capacity, and never assign wire functions from colour alone.
Route pulse wiring separately from motor and drive power cables. Use the required screened cable and terminate the screen according to the installation instructions; single-ended screen termination is not a universal rule. Tighten terminals as specified and provide strain relief so the cable does not load the sensor mechanically.
4. Configure scaling and pulse handling
On a multifunction instrument, select tachometer mode, the RPM unit and the correct pulses per revolution. Some menus request PPR, while others require a multiplier or prescale value. These are not interchangeable settings. The underlying relationship is RPM = 60 × f / P, where f is input frequency and P is the number of events actually counted per turn.
For example, 60 pulses/rev at 1500 RPM produces 1500 Hz. The sensor, input circuit and selected filter must all support that signal. Encoder ×2/×4 edge counting may change the effective P value. Set averaging to achieve the required response time, and check the zero-speed timeout separately at the lowest operating speed.
| Symptom | Check first |
|---|---|
| Shaft turns, display stays at zero | Input type, signal reference, pulse detection, HOLD |
| Reading is exactly 2× or 60× too high | Pulses/rev, multiple optical marks, edge counting |
| Reading jumps when the drive runs | Noise coupling, cable routing, sensor alignment |
5. Test the displayed value and process output
Under controlled conditions that prevent unexpected movement, test low, normal and high operating speeds. Compare readings with an independent reference to verify accuracy. For a PLC connection, match the analog scale or communication units. Test alarm thresholds, hysteresis, startup delay and behaviour after the shaft stops. A standard alarm output does not, by itself, constitute a safety function.
6. Record the final configuration
Document the model, sensor type, PPR or prescale, filtering, output scale and test results. Enable the settings lock if appropriate. Define sensor-clearance, optical-cleaning and connection checks for maintenance. These records make later troubleshooting more effective by separating wiring faults from configuration errors.
Technical references: HIOKI FT3405/FT3406: measurement preparation and adapter use · OMRON H7CX: mounting, input connections and tachometer configuration