TECHNICAL SUPPORT
Published 2026-04-29
Have you ever been curious, wondering why that little servo can stay at a certain angle so accurately? The secret is hidden in the potentiometer inside it.This video will take 3 minutes to disassemble the steering gear potentiometer and demonstrate its working principle as an "angle sensor" in an intuitive way.。
Whether you are a passionate enthusiast in the electronics field, or a beginner who has just entered the field of robot learning, this guide can help you fully understand how the servo knows its own position.
The steering gear potentiometer is fundamentally a variable resistor. Its rotating shaft and the steering gear output shaft are linked to each other. When the steering gear rotates, the resistance value of the potentiometer will change accordingly, and then output an analog voltage signal between 0V and the reference voltage. This signal is the only basis for the steering gear control chip to judge the current position.
A common case scenario is in a scenario of model aircraft operation. When you operate the aircraft model's control surface, the remote control will issue instructions. This command clearly requires the servo to rotate to the 30-degree position. at this time. If the angle corresponding to the voltage fed back by the potentiometer is 15 degrees. Then the control chip will drive the motor to continue rotating. And that spin doesn’t stop. It will continue until the angle corresponding to the feedback voltage reaches the target angle. Such a process completely demonstrates the physical basis of closed-loop control.
As you watch the video, you'll see the key steps:
1. Disassemble the servo housing and find the potentiometer at the end of the gear set (usually has three pins)
2. Use a multimeter to measure the resistance between the middle pin and the outer pin, then rotate the output shaft and observe the continuous change in resistance.
3. Connect an oscilloscope and you can see that the voltage output by the potentiometer changes linearly with the angle.
Emphasis on the core points: The servo potentiometer is an eye-like component used for position feedback. Without it, the servo would be like walking blindfolded, without knowing its own angle at all.
During actual maintenance or debugging, you can quickly determine whether the potentiometer is damaged through the video tutorial. A common situation is that if your robot's joint servo is shaking, or cannot be centered, or the rotation angle is inaccurate, then 80% of the reasons are that the potentiometer is worn or has poor contact.
Step-by-step testing method(Details will be demonstrated in the video):
When in static testing, first use the resistance range of the multimeter to measure the resistance at both ends of the potentiometer after the power is turned off. Under normal circumstances, this resistance should be the nominal value, such as 5kΩ or 10kΩ; then measure the resistance of the middle leg and either side leg. During this process, the servo output shaft must be rotated at a constant speed. At this time, the resistance value should change smoothly and there is no jump.
Send a PWM signal that exhibits a slow swing to the servo to conduct a dynamic test. Use an oscilloscope to observe the voltage waveform of the pin of the potentiometer in the middle position. The waveform when the situation is normal should be a continuous and smooth waveform that looks like a sawtooth. If there is a sharp peak or a step-like situation, it indicates that the carbon film inside the potentiometer is worn.
The voltage output by the potentiometer has a linear proportional relationship with the angle. This is the cornerstone of the working principle of all standard servos.
1. First, go to view the complete disassembly video, then, search for "Video of working principle of steering gear potentiometer”, and then give priority to tutorials with physical measurements and waveform displays.
2. Prepare tools, including a Phillips screwdriver, a digital multimeter, and an old servo. This old servo can be of any brand, and its structure is universal.
3. Hands-on verification：
Carefully disassemble the servo and be careful not to break the internal leads.
Manually rotate the output shaft, and at the same time, use the voltage range of a multimeter to measure the voltage between the middle foot of the potentiometer and the ground wire.
Record the voltage value at 0 degrees, this voltage value should be 0V, record the voltage value at 45 degrees, this voltage value should be 1.25V, record the voltage value at 90 degrees, this voltage value should be 2.5V, provided that the reference voltage is 5V.
4. If the voltage is not continuous or the range does not meet the requirements, then directly replace the potentiometer with the same specifications. This is part of common troubleshooting.
The mechanical angle is converted into an electrical signal with the help of the linear feedback mechanism of the steering gear potentiometer. This conversion constitutes the closed-loop soul of the servo system.
Q1: Can the steering gear potentiometer be replaced separately after it is damaged?
One: It can be done by disassembling the old potentiometer, purchasing a potentiometer with the same resistance and the same shaft shape, and then replacing it directly.。
Q2: Why does the potentiometer in the video have 3 pins?
A: The pins on both sides are connected to power and ground, and the middle pin outputs a divided voltage that changes with the angle.
Q3: Are the potentiometers of digital servos and analog servos the same?
The situation is the same. There is no distinction between digital and analog in the potentiometer itself. It is just that the way the control circuit processes the signal is different, and the methods used are different.
Q4: How to use video to determine whether the potentiometer is linear?
Turn the shaft slowly and see if the multimeter reading changes evenly or if the oscilloscope waveform appears as a straight slope.
Q5: Can it be measured without an oscilloscope?
That A, if you have the corresponding capabilities, you need to use the voltage range of the multimeter to measure the voltage of the middle pin, and record it every 10 degrees of rotation, and then draw a curve to see if it is close to a straight line.
Remember: anything ending with "Video of working principle of steering gear potentiometer"Based learning, in the end, you have to measure the actual object through a multimeter. Only by verifying the corresponding relationship between voltage and angle with your own hands can you truly master it. Now go and disassemble an old steering gear.
Update Time：2026-04-29
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