Technical Foundation
What Is a Tachometer Sensor?
A tachometer sensor measures rotational speed by detecting the passage of gear teeth, magnetic targets, or reflective/optical marks on a rotating shaft, producing a pulse output whose frequency is proportional to RPM. Magnetic pickup sensors are passive devices that generate their own voltage pulse as a ferrous gear tooth passes the sensor tip, requiring no external power but limited to a minimum speed threshold below which the signal becomes too weak to detect reliably.
Hall-effect and optical sensors are active devices requiring external power (commonly 5-24VDC) but can detect speed accurately down to and including zero RPM, making them the better choice for low-speed monitoring or start-up detection where a passive magnetic pickup's signal would be too weak. Output signal type (open collector, NPN/PNP, sine wave) must match the receiving tachometer display or controller's input requirement exactly.
Prefer a quick quote?
Get Tachometer Sensors Pricing in Your Inbox
Skip the search — tell us the output signal type, mounting thread and equipment being monitored and we will come back with pricing.
| Spec | What It Means | Why It Matters |
|---|---|---|
| Sensor Technology | Magnetic pickup (passive), Hall-effect, optical (active) | Passive magnetic pickups need no power but have a minimum detectable speed; active sensors read to zero RPM |
| Output Signal Type | Sine wave, square wave, NPN/PNP open collector | Must match the tachometer/controller's input specification exactly |
| Mounting Thread | Common threads like 3/4-16, M18x1.5 | Must match the equipment's sensor boss thread for correct air gap positioning |
| Target Type | Gear tooth, magnetic ring, reflective mark | Sensor type must be paired with a compatible target already on or added to the shaft |
| Air Gap Tolerance | Manufacturer-specified min/max clearance to target | Wrong gap produces weak, unreliable or false pulse signals |
Shop Tachometer Sensors
Browse Tachometer Sensors Sub-Categories
Organised by sensor technology. Pick a sub-category, or tell ChatMRO the output signal and mounting thread for an exact match.
How it works
From Half-Remembered Part Number to PO, in Three Steps.
Ask
Type an MPN, paste a spec sheet, or describe the part in plain English. ChatMRO understands engineer-speak.
Compare
Side-by-side specs, cross-references, and equivalents from multiple sources — without the clutter of endless browser tabs.
Quote & Buy
Request a quote or add to cart. Volume discounts, VAT-aware pricing, and consolidated procurement — all in one place.
Applications
Where Tachometer Sensors Get Used
Tachometer sensors are specified anywhere shaft rotational speed needs to be measured, displayed, or used as a safety or control feedback signal.
Diesel & Industrial Engines
Magnetic pickup sensors reading flywheel ring gear teeth for tachometer display and overspeed shutdown protection.
Pumps, Fans & Rotating Machinery
Speed sensors monitoring shaft RPM for condition monitoring and process control feedback.
Conveyor & Material Handling Systems
Speed sensors detecting belt or roller slowdown and stoppage for safety interlock systems.
Turbines & Generators
Precision magnetic and optical speed sensors feeding overspeed protection and governor control systems.
Motor Control & VFD Feedback
Hall-effect and encoder-based speed sensors providing closed-loop feedback for variable frequency drive control.
Marine Propulsion Systems
Magnetic pickup sensors monitoring engine and shaft RPM for bridge tachometer displays.
FAQ
Tachometer Sensors Questions, Answered
Should I choose a magnetic pickup or a Hall-effect sensor?
Magnetic pickup sensors are passive, need no external power, and are simple and rugged, but their signal weakens at low speed and disappears entirely near zero RPM, making them unsuitable for start-up or very low-speed monitoring. Hall-effect and optical sensors require external power but read accurately down to zero RPM, which matters for applications needing stall or start detection.
How do I match a sensor to my equipment's existing target (gear tooth, magnet ring)?
Check what type of target is already on the shaft — a magnetic pickup needs a ferrous gear tooth or toothed wheel, a Hall-effect sensor typically needs a magnetic target ring, and an optical sensor needs a reflective or contrasting mark. If no target exists, one will need to be added and matched to the sensor type being installed.
What air gap should I set between the sensor and the target?
Manufacturers specify a minimum and maximum air gap for reliable signal detection — too large a gap weakens the signal below the detection threshold, while too small a gap risks the sensor tip contacting and being damaged by the rotating target. Set the gap using a feeler gauge per the sensor's datasheet.
What output signal type do I need to match my tachometer or controller?
Check the receiving device's input specification — common types include sine wave (typical raw magnetic pickup output), square wave, and NPN or PNP open-collector digital outputs used by many active sensors and PLC inputs. Mismatched output/input types either won't communicate or can damage the input circuit.
Can a tachometer sensor be used for overspeed shutdown protection?
Yes, this is a common application — the sensor's pulse frequency is monitored by a speed switch or controller programmed to trigger a shutdown or alarm relay above a set RPM threshold. Confirm the sensor and monitoring device combination is rated and configured appropriately for safety-critical overspeed protection duty.
Keep browsing
Related Categories
Explore More
Find Your Next Part Now.
Describe a part number, spec or what it does.