Incremental encoderAs a core component used for speed and position detection in the field of industrial automation, its installation accuracy directly determines the reliability of detection signals and the stability of control systems. If installation deviation is not calibrated in a timely manner, it may lead to counting errors, signal jitter, abnormal equipment start stop, and even serious production accidents. This article will systematically sort out the common installation deviation types of incremental encoders, explain their calibration principles, operation methods, and key precautions in detail, and provide practical guidance for on-site debugging.

1、 Common installation deviation types and hazards of incremental encoders

The installation deviation of incremental encoders mainly comes from insufficient mechanical fitting accuracy or non-standard installation operations. The core deviation can be divided into three categories: radial deviation, axial deviation, and angular deviation, and the causes and hazards of each type of deviation are significantly different.

1.1 Radial deviation

Radial deviation refers to the center deviation between the encoder rotating shaft and the rotating shaft of the tested equipment (such as motors, ball screws) in the radial direction. It is usually caused by misalignment of the coupling installation, mismatched shaft diameter tolerances, or loose fixing of the mounting seat. This type of deviation will cause periodic changes in the gap between the encoder's internal encoder disc and the reading head, resulting in signal amplitude fluctuations. When the deviation exceeds 0.1mm (specific value needs to refer to the encoder specification book), it is easy to cause "pulse loss" phenomenon, leading to a decrease in speed detection accuracy, such as the problem of fluctuating speed during motor speed regulation.

1.2 Axial deviation

Axial deviation refers to the movement or installation position deviation of the encoder shaft along the axis direction, which is often caused by poor positioning of the equipment shaft end or excessive axial clearance of the coupling. Axial deviation can cause axial displacement of the encoder disc. If it exceeds the allowable axial movement range of the encoder (generally ± 0.5mm), it may cause mechanical friction between the reading head and the encoder disc, accelerate component wear, and disrupt the stability of signal detection, resulting in noise interference in the output signal.

1.3 Angular deviation

Angular deviation refers to the angular deviation between the encoder shaft and the equipment shaft, commonly known as "different shafts", which often occurs in scenarios where the elastic coupling is installed too tightly or the parallelism between the two shafts exceeds the tolerance. Angular deviation can cause additional radial force on the encoder shaft, leading to bearing damage and abnormal signal phase difference during long-term operation. For example, the orthogonality of phase A and B signals (normally 90 °± 45 °) is disrupted, causing the counter to be unable to accurately determine the direction of rotation and resulting in a "counting error during reverse rotation" problem.

2、 Preparation for Calibration and Adjustment

The preparation work before calibration adjustment is the foundation for ensuring operational safety and accuracy, which needs to be implemented from three dimensions: tool, equipment status, and parameter confirmation.

2.1 Preparation of Tools and Instruments

According to the deviation detection requirements, the following tools need to be prepared:

Precision testing tools: dial gauge (accuracy 0.001mm) and gauge holder, dial gauge (for rough testing), laser alignment instrument (suitable for high-precision equipment, accuracy up to 0.001mm/m);

Installation and adjustment tools: Hexagonal wrench set (matched with encoder fixing screws), torque wrench (ensure that the tightening torque of the screws meets the requirements), copper hammer (avoid damaging the shaft end by knocking), plug gauge (check clearance);

Signal detection tools: oscilloscope (bandwidth ≥ 10MHz, used to observe A, B, and Z phase signal waveforms), multimeter (to detect power and signal circuit continuity), encoder signal simulator (to assist in determining whether signal abnormalities are caused by the encoder itself).

2.2 Equipment and Safety Preparation

Firstly, the tested equipment needs to be shut down and powered off, and a "Do Not Close" sign should be hung to avoid equipment misoperation during the calibration process; Next, clean up the oil and dust on the installation site of the encoder, and check whether the coupling has defects such as wear and cracks. If there is any damage, it needs to be replaced first; Finally, confirm that the encoder power has been disconnected to avoid burning out the internal circuit due to live operation.

2.3 Parameter and specification confirmation

Refer to the technical specifications of the encoder and the tested equipment to clarify the key parameters: radial allowable deviation of the encoder (such as ≤ 0.2mm), axial allowable play (such as ± 0.3mm), shaft diameter fit tolerance (such as H7/h6), signal output type (open collector, differential output, etc.), and A/B phase orthogonal requirements; Simultaneously record the rated speed of the equipment and the connection method of the shaft end (such as key connection, tightening screw fixation), providing a basis for subsequent adjustments.

3、 Core calibration and adjustment methods

Calibration adjustment should follow the principle of "first detecting the type of positioning deviation, then making targeted adjustments, and finally verifying the effect". There are differences in the operation process of different deviation types, which need to be implemented step by step.

3.1 Calibration and adjustment of radial deviation

The core adjustment goal of radial deviation is to make the encoder shaft coincide with the radial center of the equipment shaft. The specific steps are as follows:

Installation and testing tool: Fix the dial gauge on the equipment base, so that the dial gauge probe is vertically pressed against the cylindrical surface of the encoder shaft, ensuring that the probe is tightly attached to the shaft surface without looseness;

Detection deviation value: manually rotate the equipment shaft slowly, record the maximum and minimum values of the dial gauge, and half of the difference between the two is the radial deviation value (if the maximum value is 0.3mm and the minimum value is 0.1mm, then the deviation is 0.1mm); Simultaneously observe the stability of the micrometer pointer during the rotation process to determine if the deviation is uniform;

Targeted adjustment: If the deviation is caused by the misalignment of the coupling, loosen the fixing screws of the coupling and slightly move the position of the encoder mounting seat (the height can be adjusted by adding or removing shims, or the mounting seat can be adjusted horizontally). After each adjustment, repeat step 2 until the radial deviation is ≤ the allowable value of the encoder; If the fit of the shaft diameter is too loose, it is necessary to replace the compatible coupling or add a tightening sleeve at the shaft end to ensure a firm connection;

Tightening and Review: After the adjustment is completed, tighten the encoder installation screws and coupling screws according to the required torque in the specification book (such as M3 screw tightening torque of 0.8N · m), rotate the shaft again for inspection, and confirm that the deviation is stable within the allowable range.

3.2 Calibration and adjustment of axial deviation

The key to adjusting axial deviation is to limit the axial movement of the encoder shaft. The steps are as follows:

Detecting axial movement: Place the micrometer probe vertically against the center position of the encoder shaft end face, manually push the shaft to move along the axial direction, and record the maximum change of the micrometer, which is the axial movement value;

Analyze the cause of deviation: If the movement is due to poor positioning of the equipment shaft end, it is necessary to check whether the bearing cover inside the equipment is loose, tighten the cover screws or add adjustment washers to limit the axial movement of the equipment shaft; If the axial clearance of the coupling is too large, it is necessary to replace the elastic coupling with a smaller clearance (such as a diaphragm coupling), or add a thin gasket between the coupling and the encoder shaft to eliminate the axial clearance;

Installation position calibration: If the encoder itself is installed too deep or too shallow, loosen the installation screws, adjust the axial position of the encoder on the shaft, ensure that the gap between the reading head and the encoder meets the requirements of the specification book (generally 0.2~0.5mm), and after adjustment, check the axial displacement again to ensure it is ≤ the allowable value.

3.3 Calibration and adjustment of angular deviation

The adjustment of angular deviation needs to ensure the parallelism of the two axes. For high-precision scenarios, it is recommended to use a laser alignment instrument. For conventional scenarios, the following methods can be used:

Preliminary testing: Fix the dial gauge on the coupling end faces of the encoder shaft and equipment shaft respectively, rotate the shaft once, and observe the swing amplitude of the dial gauge pointer. The larger the swing amplitude, the greater the angular deviation;

Accurate positioning: When using a laser alignment device, the transmitter and receiver are installed on the device axis and encoder axis respectively. After starting the alignment device, the device will automatically display the angular deviation values (unit: mm/m) of the two axes and adjust the direction;

Adjustment operation: Loosen the fixing screws of the encoder mounting base, and add or remove shims on the bottom or side of the mounting base according to the adjustment amount prompted by the centering instrument (the thickness of the shims needs to be accurately calculated, such as a deviation of 0.1mm/m. If the mounting base is 100mm away from the coupling, a shim of 0.01mm needs to be added or removed). During the adjustment process, multiple retests are required until the angular deviation is ≤ 0.1mm/m (high-precision equipment requires ≤ 0.05mm/m);

Signal verification: After adjusting the angular deviation, connect the encoder signal to the oscilloscope and observe the waveforms of phase A and B signals to ensure that the phase difference between the two is 90 °± 10 ° and there is no significant phase drift.

3.4 Auxiliary calibration at the signal level

Partial installation deviations may be reflected through signal anomalies, which can be assisted by signal calibration to determine the adjustment effect:

Power stability check: Use a multimeter to detect the encoder power supply voltage (such as DC5V or DC24V), ensuring a fluctuation range of ≤± 5%. If the voltage is unstable, check the filtering capacitor of the power supply circuit or replace the voltage regulator;

Waveform observation: When the oscilloscope is connected to phase A and B signals, the normal waveform should be a square wave with stable amplitude (such as differential output amplitude ≥ 2V) and no obvious clutter or distortion; If there is a fluctuation in waveform amplitude, the radial deviation needs to be rechecked; If there is an abnormal phase difference, the angular deviation needs to be rechecked;

Counting verification: Connect the encoder to the PLC or counter, manually rotate the shaft for a fixed number of turns (such as 100 turns), observe the difference between the displayed value of the counter and the theoretical value (encoder wire count x number of turns). If the error is ≤ 1 pulse, it indicates that the calibration is qualified.

4、 Verification and maintenance after calibration

Calibration adjustment is not a one-time solution, it requires multidimensional verification to ensure effectiveness and establish a long-term maintenance mechanism.

4.1 Operational verification

Power on the equipment for trial operation, continuously running at rated speed for 1-2 hours, with a focus on monitoring: whether the speed display is stable (without jumping), whether the counting is accurate when the load changes, and whether there are signal abnormalities during equipment start stop and forward/reverse rotation; At the same time, use an infrared thermometer to detect the temperature of the encoder housing, ensuring it is ≤ 60 ℃ (to avoid excessive temperature affecting signal stability).

4.2 Key points of regular maintenance

Daily inspection: Clean the dust on the surface of the encoder every week, check if the installation screws and couplings are loose, and rotate the shaft by hand to feel if there is any jamming phenomenon;

Regular calibration: Based on the operating environment of the equipment (such as scenes with high dust and vibration), re check the installation deviation every 3-6 months to ensure that the deviation does not exceed the allowable range;

Signal circuit maintenance: Check if the shielding layer of the signal cable is well grounded every six months (grounding resistance ≤ 4 Ω) to avoid electromagnetic interference causing signal abnormalities.

5、 Common Problems and Solutions

Question 1: Does "pulse loss" still occur after calibration? Solution: Check if the signal cable is too long (recommended ≤ 50m) or if shielded wires are not used. You can add signal repeaters or replace differential output encoders; At the same time, verify the radial deviation. If there is significant vibration during equipment operation, it is necessary to add shock-absorbing gaskets to the encoder mounting seat.

Question 2: Is the phase difference between phase A and phase B always abnormal? Solution: Confirm whether the encoder rotation direction matches the signal definition. If the direction is opposite, switch the A and B phase wiring; If the wiring is correct, recheck the angular deviation and replace the high-precision coupling if necessary.

Question 3: Axial movement cannot be eliminated? Solution: If the equipment shaft itself moves too much, maintenance or replacement of the equipment bearings is required. Adjusting the encoder alone cannot completely solve the problem.

VI. Summary

　　Incremental encoderThe calibration and adjustment of installation deviation should be based on mechanical accuracy and signal verification as the core. By accurately detecting the type of positioning deviation, targeted radial, axial, and angular adjustments can be implemented, combined with operational verification and regular maintenance, to ensure the reliability of the encoder output signal. In practical operation, it is necessary to strictly follow the requirements of the equipment specification book to avoid mechanical damage caused by excessive adjustment, while paying attention to safety regulations to ensure efficient and safe completion of calibration work.