Moving Coil Mechanism for Tachometers

Product Specifications

Technical details and manufacturing context for Moving coil mechanism

Definition

The moving coil mechanism is a precision electromechanical component used as the core sensing and indicating element in tachometers. It consists of a lightweight coil wound on an aluminum or plastic former, suspended in a permanent magnetic field created by magnets such as Alnico or Neodymium. The magnetic circuit and frame are made of steel, and the coil is supported by pivot bearings or taut-band suspension. When a current proportional to the rotational speed being measured flows through the coil, it generates a torque that rotates the coil against a restoring spring, moving an attached pointer across a calibrated scale to display speed. The mechanism operates on the principle of electromagnetic torque: the current-carrying coil in a radial magnetic field experiences a Lorentz force, producing a torque proportional to the current. This torque rotates the coil assembly until balanced by the counter-torque of a spiral spring, with the angular deflection indicating the speed. Key parameters include rated voltage (24 V DC ±10%), coil resistance (20–100 Ω), maximum current (0.5–2.0 A), torque (0.05–0.5 N·m), rotation angle (0–90°), linearity (±0.5%), hysteresis (≤0.3%), response time (≤10 ms), operating temperature (-20 to 70 °C), storage temperature (-40 to 85 °C), ingress protection (IP54–IP65 per IEC 60529), insulation class (F per IEC 60085), and weight (0.1–0.5 kg). These values are reference ranges; verify model-specific specifications with the manufacturer. The mechanism is designed for use in tachometers and similar indicating instruments. Proper selection requires considering the required voltage, resistance, torque, and environmental conditions. Maintenance signals include erratic pointer movement, excessive heating, or loss of accuracy. Failure boundaries include exceeding maximum current, which may cause overheating and demagnetization, or operating outside the temperature range, which may degrade performance and insulation.

Working Principle

The moving coil mechanism converts electrical current into rotational motion via electromagnetic torque. A current proportional to the measured speed passes through a coil in a radial magnetic field. The Lorentz force on the coil creates a torque proportional to the current, rotating the coil assembly. A spiral spring provides a counter-torque, and equilibrium is reached when the torques balance. The angular deflection is proportional to the current, thus indicating speed. The mechanism's response time is ≤10 ms, and linearity is ±0.5%.

Common Materials

Copper wire (coil winding), Aluminum or plastic (coil former), Permanent magnet (e.g., Alnico, Neodymium), Steel (magnetic circuit and frame), Pivot bearings or taut-band suspension

Technical Parameters

Parameter	Typical range	Notes & selection driver
Rated Voltage	24 ±10% V DC	Standard coil voltage; other voltages available on request.
Coil Resistance	20–100 Ω	Determines current draw and power consumption.
Maximum Current	0.5–2.0 A	Exceeding this may cause overheating and demagnetization.
Torque	0.05–0.5 N·m	Continuous torque at rated voltage.
Rotation Angle	0–90 °	Mechanical stop limits rotation.
Linearity	±0.5 %	Deviation from ideal linear relationship between current and angle.
Hysteresis	≤0.3 %	Maximum difference in output for same input in forward and reverse directions.
Response Time	≤10 ms	Time to reach 90% of final position after step input.
Operating Temperature	-20–70 °C	Outside this range, performance degrades and coil insulation may fail.
Storage Temperature	-40–85 °C	Non-operating condition.
Ingress Protection	IP54–IP65	Higher rating for dusty or wet environments.IEC 60529
Insulation Class	F	Class F allows 155°C hot spot temperature.IEC 60085
Weight	0.1–0.5 kg	Depends on torque rating and housing material.

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM

Moving Coil Part
The current-carrying element that rotates within the magnetic field to generate deflecting torque.

Material: Copper wire wound on a lightweight former
Permanent Magnet Part
Provides a constant, uniform radial magnetic field in the air gap where the coil rotates.

Material: Alnico, Samarium-Cobalt, or Neodymium alloy
Core and Pole Pieces Part
Forms the magnetic circuit to concentrate and direct the magnetic flux through the coil's air gap.

Material: Soft iron or steel
Spiral Spring (Hairspring) Part
Provides the restoring torque to balance the electromagnetic torque and returns the pointer to zero when no current flows.

Material: Phosphor bronze or similar spring alloy
Pointer and Scale Part
Pointer attached to the coil shaft indicates the measured value on a fixed, calibrated scale (in RPM or similar units).

Material: Aluminum (pointer), Aluminum or plastic (scale)
Pivot Bearings or Taut Band Part
Supports the moving coil assembly, allowing low-friction rotation. Taut bands also provide the restoring torque.

Material: Sapphire/jewel (bearings), Phosphor bronze (taut band)

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Moving coil mechanism.

Applied To / Applications

This component is essential for the following industrial systems and equipment:

Tachometer

View system integration details

Manufacturers of Moving coil mechanism

Manufacturer profiles associated with Moving coil mechanism.

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Frequently Asked Questions

What is the typical rated voltage for a moving coil mechanism?

The rated voltage is typically 24 V DC ±10%, but other voltages may be available on request. Always verify the exact rating for your specific model.

What materials are used in the moving coil mechanism?

Common materials include copper wire for the coil, aluminum or plastic for the former, permanent magnets (e.g., Alnico, Neodymium), steel for the magnetic circuit and frame, and pivot bearings or taut-band suspension.

What is the maximum current the coil can handle?

The maximum current is typically 0.5–2.0 A. Exceeding this may cause overheating and demagnetization, so it is important to stay within the specified range.

What environmental conditions can the mechanism withstand?

The operating temperature range is -20 to 70 °C, and storage temperature is -40 to 85 °C. Ingress protection is IP54–IP65 per IEC 60529, and insulation class is F per IEC 60085. Verify these ratings for your application.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records.

Preliminary Technical Classification

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pressure:	Atmospheric to 2 bar (typical), vacuum compatible
other spec:	Current range: 0-500 mA continuous, 1A peak; Voltage: 5-48 VDC; Speed: 0-10,000 RPM; Torque: 0.1-50 mNm
temperature:	-40°C to +85°C (operational), up to +125°C (peak)

Moving coil mechanism

Product Specifications

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