Rotational speed sensors: 50 selection, application and maintenance questions

A speed sensor generates events from teeth, marks or magnetic-field changes; frequency or period is converted into rotational speed. Variable-reluctance, Hall and other principles have different power, low-speed and target limits. The principle explains signal generation; it does not establish the range, accuracy, materials or approvals of every model. Review the physical principle and the application limits separately.

Verification: Confirm "Minimum, normal and maximum speed and response time" and assess "Passive magnetic amplitude depends on speed and gap; standstill capability must not be assumed" against the actual application. Record the complete model and document revision used.

适用边界：Passive magnetic amplitude depends on speed and gap; standstill capability must not be assumed

Define the quantity to be accepted before selecting a display unit. A speed sensor generates events from teeth, marks or magnetic-field changes; frequency or period is converted into rotational speed. Variable-reluctance, Hall and other principles have different power, low-speed and target limits. For "Minimum, normal and maximum speed and response time", document output definitions and conversion or compensation conditions; displaying a value does not make it a direct measurement under all conditions.

Verification: Document the process objective, units and reference conditions. Check "Treating frequency in hertz as rpm directly" and list separate inputs and acceptance methods for calculated results.

适用边界：Treating frequency in hertz as rpm directly

Prepare at least these five input groups: Minimum, normal and maximum speed and response time; Effective pulses per revolution, tooth geometry and target material; Working gap, eccentricity, vibration and temperature; Output circuit, supply and receiver capability; Standstill, direction, overspeed or underspeed requirements. Mark unknown items for confirmation instead of substituting a normal point or an assumed default for all conditions.

Verification: Have process, instrumentation and purchasing roles agree the inputs, particularly "Effective pulses per revolution, tooth geometry and target material". Resolve missing evidence before requesting application confirmation.

适用边界：Passive magnetic amplitude depends on speed and gap; standstill capability must not be assumed

Select the range from actual operating conditions and permissible error, then check extremes and installation constraints. For this family: Passive magnetic amplitude depends on speed and gap; standstill capability must not be assumed Nominal size or maximum equipment rating need not equal the useful measuring interval.

Verification: List minimum, normal, maximum and abnormal conditions. Check "Working gap, eccentricity, vibration and temperature" against the documented performance envelope.

适用边界：Passive magnetic amplitude depends on speed and gap; standstill capability must not be assumed

No. Low-end usability depends on the principle, available signal and error mechanisms. Maximum pulse frequency depends on speed and pulses per revolution More display digits, software scaling or a stated turndown cannot remove the original noise or installation error.

Verification: Obtain error definitions and limits at the actual low operating point. Use "Fixed ratio error: inspect tooth count, counted edges and units" to investigate bias instead of comparing only percent-of-full-scale values.

适用边界：Maximum pulse frequency depends on speed and pulses per revolution

Use the complete measured object and actual exposure, rather than a material name alone. Output circuit, supply and receiver capability Avoid this family-specific misuse: Selecting input bandwidth from normal speed alone For non-wetted equipment, assess loads, target materials, signals and environmental compatibility instead.

Verification: List the actual contact or loading parts, seals, insulation and cleaning conditions. Have the responsible parties assess "PLC scan and input filtering can miss narrow pulses".

适用边界：PLC scan and input filtering can miss narrow pulses

Normal measurement, temporary excursions and survival limits are different requirements. PLC scan and input filtering can miss narrow pulses Start-up, cleaning, impacts, power interruption or abnormal environments can determine the necessary construction and protection.

Verification: Complete the worst-case conditions using "Standstill, direction, overspeed or underspeed requirements" and check "Frequency from one pulse channel generally does not establish direction". Separate continuous operating limits from temporary limits in the specification.

适用边界：Frequency from one pulse channel generally does not establish direction

Not without assessment. Verify sensing against a traceable speed reference and conversion with known frequency, stating pulses per revolution; injected frequency does not test target geometry, gap or low-speed signal generation. The installed system also includes object, mounting, signal conversion, environmental and reference effects. Derived results additionally depend on the relevant input uncertainties.

Verification: Agree actual test points, installation conditions and the acceptance reference. Check "Install at a permitted target/gap and inspect full-revolution eccentricity" and document the system error or uncertainty basis.

适用边界：Maximum pulse frequency depends on speed and pulses per revolution

A stable indication and fast change detection involve a trade-off; filtering cannot repair incorrect installation or real process variation. Jitter: inspect gap, tooth defects, narrow pulses and noise Review the complete chain when fast response matters, not merely the display refresh rate.

Verification: Define the shortest relevant event and acceptable delay. Check "Verify pulses, edge counting, conversion and start-up delay" and verify local output, display and receiving-system response using a controlled change.

适用边界：Assuming pulse generation guarantees reliable standstill diagnosis

Typical contexts include: Motor and conveyor speed detection; Gear or shaft pulse counting; Verified underspeed or overspeed monitoring. Similar application labels do not establish equivalent conditions. In particular, assess "Frequency from one pulse channel generally does not establish direction" before relying on another installation as proof.

Verification: Select the nearest application and compare "Minimum, normal and maximum speed and response time" and "Standstill, direction, overspeed or underspeed requirements". Obtain written confirmation where published application limits are exceeded.

适用边界：Frequency from one pulse channel generally does not establish direction

Translate required functions, performance and physical interfaces into verifiable options. Principle, minimum speed and maximum frequency; Target geometry/material, gap and mounting. Options affecting suitability or supply scope should be explicit; terms such as standard or same as existing are insufficient.

Verification: Check the complete order code and selection sheet, especially "Working gap, eccentricity, vibration and temperature". List accessories, documents, calibration and delivery boundaries separately.

适用边界：Treating frequency in hertz as rpm directly

Install at a permitted target/gap and inspect full-revolution eccentricity The installation drawing must match the available space and process or mechanical structure. Access for fitting and servicing should be established before delivery.

Verification: Review a dimensioned, oriented site drawing. Use "Output circuit, supply and receiver capability" and "PLC scan and input filtering can miss narrow pulses" to confirm connections, support, removal access and safe isolation.

适用边界：PLC scan and input filtering can miss narrow pulses

Match NPN/PNP, voltage or passive signals to the receiver Supporting conditions are part of the measurement system. Matching mechanical connections or signal names alone do not establish power, I/O, grounding or configuration compatibility.

Verification: Confirm "Output circuit, power, polarity and input threshold" and "Pulse count, direction, standstill and delay logic" against actual terminals, loops and receiving-system settings.

适用边界：Selecting input bandwidth from normal speed alone

Check identity, installation and basic conditions first, then status, output and process response. Verify pulses, edge counting, conversion and start-up delay Preserve original evidence for unexplained anomalies instead of concealing them with zero or factor adjustments.

Verification: Record factory settings and initial status. Investigate "No low-speed value: inspect principle limits, amplitude and timeout" step by step and change parameters only after identifying the cause and using an authorised procedure.

适用边界：Assuming pulse generation guarantees reliable standstill diagnosis

No. Establish the represented object and reference conditions: Principle, minimum speed and maximum frequency. Electrical equipment also needs loop type, scaling, failure behaviour and protocol details checked. Mechanical indicators require clear boundaries between indication and remote-transmission accessories.

Verification: Check the receiving-system variable against "Minimum, normal and maximum speed and response time" and verify limits, units and abnormal states with the actual equipment. Record wiring, configuration and end-to-end checks against "Match NPN/PNP, voltage or passive signals to the receiver".

适用边界：Selecting input bandwidth from normal speed alone

Verify sensing against a traceable speed reference and conversion with known frequency, stating pulses per revolution; injected frequency does not test target geometry, gap or low-speed signal generation. The report should identify the delivered instrument, measured quantity, conditions, method and results. A general conformity certificate does not establish performance for every option or operating condition.

Verification: Check serial number, points, units, reference equipment and traceability. Compare "Effective pulses per revolution, tooth geometry and target material" with the calibrated conditions and agree separate acceptance where they differ.

适用边界：Maximum pulse frequency depends on speed and pulses per revolution

Verify low/normal/high speeds and standstill/fault behaviour with a reference Agree criteria before testing, including range, conditions, error definition and treatment of anomalies. Similar-looking readings or an unsuitable portable reference are not sufficient acceptance evidence.

Verification: Choose an appropriate reference using "Verify sensing against a traceable speed reference and conversion with known frequency, stating pulses per revolution; injected frequency does not test target geometry, gap or low-speed signal generation.". Record "Minimum, normal and maximum speed and response time" and test conditions; investigate "Fixed ratio error: inspect tooth count, counted edges and units" before deciding on rework or recalibration.

适用边界：Maximum pulse frequency depends on speed and pulses per revolution

Define why the standard supply is insufficient, the required verification and the responsible parties. Frequency from one pulse channel generally does not establish direction; Replacing unverified overspeed protection with a generic PLC program. Additional materials, construction, documents or tests depend on actual requirements.

Verification: Attach "Standstill, direction, overspeed or underspeed requirements" and the deviations. Obtain technical confirmation, additional charges, delivery conditions and acceptance methods; unknown requirements must not be assumed satisfied.

适用边界：Frequency from one pulse channel generally does not establish direction

No low-speed value: inspect principle limits, amplitude and timeout Distinguish the actual measured condition from device-state and readout or transmission faults. Do not immediately interpret missing data as sensor failure or a zero process value.

Verification: Under appropriate safe isolation, check "Match NPN/PNP, voltage or passive signals to the receiver". Compare local and receiving-end status and record when the fault appeared.

适用边界：Treating frequency in hertz as rpm directly

Jitter: inspect gap, tooth defects, narrow pulses and noise Compare independent process evidence and raw signals before deciding whether installation, interference or equipment is responsible. More filtering can hide a real abnormal event.

Verification: Keep conditions comparable and record correlation with process or equipment events. Check "Install at a permitted target/gap and inspect full-revolution eccentricity" and change one factor at a time.

适用边界：Assuming pulse generation guarantees reliable standstill diagnosis

Fixed ratio error: inspect tooth count, counted edges and units Systematic bias can arise from units, reference conditions, configuration, installation or the reference method. An unexplained correction can move one operating-point error to other conditions.

Verification: Align quantities, time bases and units first. Review the reference using "Verify sensing against a traceable speed reference and conversion with known frequency, stating pulses per revolution; injected frequency does not test target geometry, gap or low-speed signal generation." and confirm that "Effective pulses per revolution, tooth geometry and target material" matches the configuration.

适用边界：Maximum pulse frequency depends on speed and pulses per revolution

Nonzero at stop: inspect spurious pulses, held values and standstill logic Establish a genuine, stable reference condition that meets the method requirements before considering adjustment. Some instruments have no freely adjustable site zero.

Verification: Check "Verify pulses, edge counting, conversion and start-up delay" and "Verify sensing against a traceable speed reference and conversion with known frequency, stating pulses per revolution; injected frequency does not test target geometry, gap or low-speed signal generation." and retain before-and-after results. If the conditions cannot be established, remove external effects or use a qualified service.

适用边界：Assuming pulse generation guarantees reliable standstill diagnosis

Under-reading at high speed: inspect bandwidth, filters and counter overflow Intermittent faults need correlated event records, not just a normal display after recovery. Review alarm settings, communication status and actual process abnormalities separately.

Verification: Retain time, status codes, raw trends and the contemporaneous "Standstill, direction, overspeed or underspeed requirements". Compare "Match NPN/PNP, voltage or passive signals to the receiver" and "Verify pulses, edge counting, conversion and start-up delay" to locate the failing link.

适用边界：Replacing unverified overspeed protection with a generic PLC program

Repeated failures warrant a common-cause assessment. Replacing unverified overspeed protection with a generic PLC program If the external conditions remain unchanged, an identical construction or installation can experience the same failure again.

Verification: Summarise failed parts, service time and "Standstill, direction, overspeed or underspeed requirements". Check "Install at a permitted target/gap and inspect full-revolution eccentricity" and "PLC scan and input filtering can miss narrow pulses" and establish corrective action before selecting repair or redesign.

适用边界：PLC scan and input filtering can miss narrow pulses

Verify sensing against a traceable speed reference and conversion with known frequency, stating pulses per revolution; injected frequency does not test target geometry, gap or low-speed signal generation. A comparison identifies differences; adjustment changes indication or parameters; calibration establishes a reference relationship under stated conditions. They are not interchangeable claims.

Verification: Define what performance and evidence must be established, using conditions relevant to "Effective pulses per revolution, tooth geometry and target material". Retain original and adjusted results, references and responsibility records.

适用边界：Maximum pulse frequency depends on speed and pulses per revolution

The same basic model does not establish identical options, software, calibration or accessories. Pulse count, direction, standstill and delay logic; System evidence for duties such as overspeed protection. Previous system operation does not remove the need to verify a replacement.

Verification: Compare full order codes and revisions. Recheck critical points, failure states and interfaces using "Verify low/normal/high speeds and standstill/fault behaviour with a reference" before handover.

适用边界：Replacing unverified overspeed protection with a generic PLC program

No. Passive magnetic amplitude depends on speed and gap; standstill capability must not be assumed Maximum values usually relate to particular options and conditions. Temperature, load, pressure, materials, speed or signal conditions may constrain one another.

Verification: Review "Working gap, eccentricity, vibration and temperature" and "Standstill, direction, overspeed or underspeed requirements" together. Obtain confirmation for the combined conditions instead of assembling unrelated maxima from separate pages.

适用边界：Passive magnetic amplitude depends on speed and gap; standstill capability must not be assumed

No. No low-speed value: inspect principle limits, amplitude and timeout Indication, measurement and transmission have distinct possible failure modes. Also consider "Treating frequency in hertz as rpm directly"; establish the actual process condition independently.

Verification: Check available status or failure indications and "Output circuit, power, polarity and input threshold". For interlocks, follow the complete safety design rather than substituting a zero value for diagnosis.

适用边界：Treating frequency in hertz as rpm directly

No. Verify sensing against a traceable speed reference and conversion with known frequency, stating pulses per revolution; injected frequency does not test target geometry, gap or low-speed signal generation. Test points and directions must reflect the working interval, relevant error mechanisms and acceptance purpose. Multiple points, reversal or load tests depend on the method.

Verification: Define acceptance coverage against "Effective pulses per revolution, tooth geometry and target material" and include critical operating points. Mark conditions outside the tests as unverified.

适用边界：Maximum pulse frequency depends on speed and pulses per revolution

Not necessarily. Options should serve the required objective; excess configuration can add cost, complexity or incompatibility. Maximum pulse frequency depends on speed and pulses per revolution; Selecting input bandwidth from normal speed alone. Establish essential requirements before comparing optional benefits.

Verification: Document the objective in "Minimum, normal and maximum speed and response time" and why "Principle, minimum speed and maximum frequency" is needed. Compare performance at actual working points rather than one headline metric.

适用边界：Maximum pulse frequency depends on speed and pulses per revolution

Not independently of risk and history. Verify sensing against a traceable speed reference and conversion with known frequency, stating pulses per revolution; injected frequency does not test target geometry, gap or low-speed signal generation. Intervals depend on applicable law or contract, conditions, drift, maintenance and failure evidence. Generic advice cannot replace mandatory requirements.

Verification: Use "Nonzero at stop: inspect spurious pulses, held values and standstill logic" and "Replacing unverified overspeed protection with a generic PLC program" to establish and review an initial plan. Retain the justification and approval for interval changes.

适用边界：Replacing unverified overspeed protection with a generic PLC program

Physical fit is insufficient. Target geometry/material, gap and mounting; Output circuit, power, polarity and input threshold. Matching, materials, signals, calibration and approval boundaries can change with the combination.

Verification: Check the complete combination against "Match NPN/PNP, voltage or passive signals to the receiver" and obtain compatibility and acceptance evidence. An unconfirmed assembly must not be described as an approved system.

适用边界：Selecting input bandwidth from normal speed alone

Check the exact order configuration and valid documents rather than a series name. System evidence for duties such as overspeed protection "Frequency from one pulse channel generally does not establish direction" also matters; certificates, installation conditions and restrictions together define suitability.

Verification: Obtain certificate identifiers, covered models and special conditions and match them to the site. Similar names do not grant functional-safety or legal-metrology approval.

适用边界：Frequency from one pulse channel generally does not establish direction

Establish the chain from quantity definition and application limits through configuration, mounting, reference and operating status. Verify low/normal/high speeds and standstill/fault behaviour with a reference A normal indication or brochure alone cannot demonstrate continuing system reliability.

Verification: Put "Minimum, normal and maximum speed and response time", "Verify sensing against a traceable speed reference and conversion with known frequency, stating pulses per revolution; injected frequency does not test target geometry, gap or low-speed signal generation." and "Under-reading at high speed: inspect bandwidth, filters and counter overflow" into the technical, acceptance and maintenance records, with responsibility for reviewing excursions.

适用边界：Frequency from one pulse channel generally does not establish direction

Possibly, after a full configuration and application comparison. A basic model name or matching output is not proof of equivalent replacement. Principle, minimum speed and maximum frequency; Target geometry/material, gap and mounting; Output circuit, power, polarity and input threshold. Record conclusions on material differences.

Verification: Provide the original full order code, data sheet and site conditions. Check "Pulse count, direction, standstill and delay logic" and "System evidence for duties such as overspeed protection" and obtain the necessary test and approval evidence before replacement.

适用边界：Frequency from one pulse channel generally does not establish direction

Base the decision on project compliance and documented delivery or service, rather than a slogan. "Minimum, normal and maximum speed and response time" and "Passive magnetic amplitude depends on speed and gap; standstill capability must not be assumed" are important family-specific checks. Claim only benefits supported by the offered product documents and written commitments.

Verification: Request the proposed configuration matching "Principle, minimum speed and maximum frequency", test evidence and delivery/service terms. Do not infer unverified performance, approvals, origin or service life.

适用边界：Passive magnetic amplitude depends on speed and gap; standstill capability must not be assumed

Use identical conditions and supply boundaries. Principle, minimum speed and maximum frequency; Output circuit, power, polarity and input threshold; System evidence for duties such as overspeed protection. Quotes with different ranges, compensation, accessories or calibration scope can conceal material differences.

Verification: Compare "Effective pulses per revolution, tooth geometry and target material", "Maximum pulse frequency depends on speed and pulses per revolution" and mounting/acceptance conditions. Separate demonstrated, unverified and inapplicable items; do not claim unproven overall superiority.

适用边界：Maximum pulse frequency depends on speed and pulses per revolution

Compare complete supply and use-cycle costs, not only the main instrument price. Install at a permitted target/gap and inspect full-revolution eccentricity; Verify sensing against a traceable speed reference and conversion with known frequency, stating pulses per revolution; injected frequency does not test target geometry, gap or low-speed signal generation. List the actual installation, supporting equipment, calibration, consumables, downtime and service requirements without assuming any brand is always cheaper.

Verification: Use the same "Principle, minimum speed and maximum frequency" configuration and "Standstill, direction, overspeed or underspeed requirements" boundary. Separate equipment, accessories, commissioning and maintenance responsibilities and retain a traceable comparison.

适用边界：Frequency from one pulse channel generally does not establish direction

For z effective events per revolution, rpm=60f/z with f in events per second. The value of z must match the events actually counted, not an assumed tooth count.

Verification: Confirm z with a known speed and full-revolution record, including double-edge or multiple-mark counting.

适用边界：Passive magnetic amplitude depends on speed and gap; standstill capability must not be assumed

With one counted pulse per tooth, the frequency is 3000 Hz. Pulse width, duty cycle and system margin still matter, not only the sensor’s maximum frequency.

Verification: Verify sensor, receiver, filtering and counter performance at this frequency and relevant peaks.

适用边界：Maximum pulse frequency depends on speed and pulses per revolution

Its output depends on changing magnetic flux; lower speed or larger gap can reduce amplitude below the receiver threshold. Rescaling cannot create standstill sensing.

Verification: Inspect the low-speed waveform safely and check gap, target, threshold and specified operating limits.

适用边界：PLC scan and input filtering can miss narrow pulses

Hall devices normally need specified power and output conditioning, unlike passive pickups. Verify the actual wiring and NPN/PNP or voltage interface.

Verification: Check supply, output and receiver terminal by terminal rather than inferring from colours or wire count.

适用边界：Frequency from one pulse channel generally does not establish direction

Check rising/falling-edge counting, double marks and pulses-per-revolution settings. A fixed ratio often reflects event definition rather than sensor calibration.

Verification: Record actual events over one revolution and compare software counting with mechanical teeth.

适用边界：Passive magnetic amplitude depends on speed and gap; standstill capability must not be assumed

Filtering, scan time or pulse-width limits can lose events. A flashing indicator does not prove all edges are captured; use suitable counting hardware and timing.

Verification: Check minimum pulse width and frequency limits and verify counting with a reference signal.

适用边界：Maximum pulse frequency depends on speed and pulses per revolution

If it provides only periodic events without direction coding, frequency alone contains no direction. Additional phase information or an explicit direction-capable scheme is needed.

Verification: Review the direction scheme and verify channels and signs with an approved reversal test.

适用边界：PLC scan and input filtering can miss narrow pulses

No next pulse can mean standstill or very low speed. Detection depends on timeout and minimum-speed requirements, creating a timing trade-off.

Verification: Calculate maximum interval at minimum speed and verify both standstill and slow-motion cases.

适用边界：Frequency from one pulse channel generally does not establish direction

The delay suppresses a defined alarm and excessive duration can hide a jam or drive failure. Base it on actual acceleration and approved risk requirements.

Verification: Record start-up behaviour and verify credible failures such as jamming before approving the delay.

适用边界：Passive magnetic amplitude depends on speed and gap; standstill capability must not be assumed

Eccentricity changes gap/amplitude and a missing tooth changes event timing, potentially disturbing period-based speed. Distinguish geometry from real speed variation.

Verification: Inspect gap and teeth over a revolution and correlate waveforms with position or an independent reference.

适用边界：Maximum pulse frequency depends on speed and pulses per revolution

No. It verifies reception and conversion, not target, gap, low-speed amplitude, mounting or interference. The installed sensing path needs separate checks.

Verification: Document injection and actual low/middle/high-speed checks separately, including standstill.

适用边界：PLC scan and input filtering can miss narrow pulses

No. Protection also involves independence, diagnostics, logic, actuation and validation. A measurement or alarm alone does not establish the complete safety capability.

Verification: Review the complete chain’s documents, tests and change control against OEM and project requirements.

适用边界：Frequency from one pulse channel generally does not establish direction