Common Faults and Symptoms of Magnetic Scale Read Heads

Magnetic Scale uses a method similar to audio recording to record magnetic pulses at strictly equal intervals on a magnetic tape (or disk); this process is called magnetic recording. A scale with recorded magnetic pulses is called a magnetic scale. The distance between adjacent grating pulses on the magnetic scale is called the magnetic grating wavelength, also known as the grating pitch. So what problems may occur during the use of a magnetic scale?

When powered on, the magnetic scale has no response and the metric/imperial indicator does not light. Possible causes:

1) Power cable not connected properly; for example, loose power cable; fuse blown.

2) The magnetic scale fuse may have blown.

The read head of a magnetic scale operates similarly to a sliding potentiometer, functioning as a voltage divider that displays the measured position via relative voltage. Therefore, several requirements should be met:

1. Stable supply voltage

Industrial power should have stability of ±0.1%. For example, with a reference voltage of 5V, a fluctuation of ±0.01V is acceptable; otherwise display fluctuations may occur. If the display fluctuation does not exceed the supply voltage fluctuation, the readout is considered normal.

2. Sufficient power capacity

If the power supply capacity is too small, during molding motion the display may jump, or melting motion may cause display fluctuations. Especially when the solenoid valve drive and the read head share the same supply, the above issues are more likely; a multimeter can detect such voltage fluctuations. If static and high-frequency interference and alignment issues have been ruled out, consider that the power supply capacity may be insufficient.

3. Electrostatic and high-frequency interference

Electrostatic interference and RF interference can easily cause the readout digits to jump. Keep power wiring separate from the read head signal wiring. The read head should be solidly grounded; measure resistance between the read head cover screws and the mounting bracket—this should be less than 1 Ω. Use shielded signal cables and ground the shield at the control cabinet end. For electrostatic interference, shorting the read head cover screw to a machine metal point with a wire often immediately eliminates the problem. High-frequency interference is harder to eliminate; try stopping robot arms or variable-frequency drives to verify the source.

4. Proper mechanical alignment

Angular tolerance should be within ±12°, parallelism within ±0.5mm. Excessive angular or parallel errors can cause display jumping; adjust angle and parallelism when necessary.

5. Aged read heads

Seals may age, allowing contaminants, oil and water ingress that affect brush contact resistance and cause display jumping—this indicates early device wear.

6. Periodic display jump at a fixed position

Check whether the cable insulation is damaged and intermittently contacts the machine metal frame causing ground faults.

Features of Atonm (Guangzhou) Intelligent Technology Co., Ltd. MRR series magnetic scale read heads:

High reliability: all-metal housing, imported flexible wear-resistant shielded cable, interference-resistant hardware and software design;

High precision: selectable resolutions 1 μm, 5 μm, 10 μm, or custom per customer; parallel installation minimizes mechanical conversion errors;

High environmental adaptability: resistant to oil, liquids, dust and vibration;

Easy installation: differential or single-ended pulse outputs; compact design for tight-space mounting.

Magnetic Scale is used in many machine tool retrofits to improve display precision across equipment such as cutting saws, angle cutting saws, mitering machines, automated end-face milling machines, CNC machining centers, lathes, milling machines, grinders, drilling machines, EDM, boring mills, portal milling machines and more.