In today's digital environment, the integration of electronic devices allows engineers to precisely control the movement of the hydraulic cylinders. The hydraulic cylinder sensors always enable this by providing fast, accurate information about the cylinder position, which can be used to control and automate cylinder movements with extremely high precision and reliability. The working principle of hydraulic cylinder position sensor.
For the hydraulic cylinder sensors, there are three main technologies to detect the cylinder position: the magnetostrictive sensor (MLDT), the potential sensor, and the variable inductance sensor (LVIT) sensor. In most cases, the hydraulic cylinder sensor usually consists of a long probe or a wire inserted into a hole drilled at the end of the cylinder stem. In this paper, we discuss the different ways in which these devices detect the cylinder position and the pros and cons of each technique.
1) Magnetic-induced hydraulic cylinder position sensor:
Magnetostrictive sensors (also known as LDT or MLDT) use magnetic fields and phenomena called "torsional strain" to make accurate cylinder position measurements. In this technique, a short current pulse is applied to the wire (probe), and when the current pulse reaches the magnet, it causes a small distortion and travels down as a wave. The sensor measures the proportion of time taken to send each pulse and receive the torsional wave, thereby telling the distance of the sensor magnet. This is a very accurate, fast method for determining the position of the magnet, which makes it well suited for applications that require precision. On the downside, the magnetostrictive sensor pair Shock and vibration are very sensitive, which makes it vulnerable in some applications.
2) Potential sensor:
Potential sensors are a more cost-effective method to locate the hydraulic cylinder, but with lower accuracy. These sensors work by measuring the resistance to the current (the conductor is proportional to its length). The system has sliding contacts that extend along a probe mounted within the cylinder. The resistance of the contact determines the position along the length of the probe. Therefore, by measuring the resistance, we can calculate the elongation of the hydraulic cylinder. The potential sensors are very robust and more resistant to shock and vibration. However, because some reciprocating parts make physical contact, this makes them easier to wear and damage, and this may guide To increase maintenance costs in high-frequency applications.
3) Linear variable inductance sensor:
Linear variable inductive sensor (LVIT) position sensor has several advantages. They have comparable accuracy to magnetostrictive sensors, but have better tolerance to shock and vibration, making them ideal for mobile devices or stationary device applications that withstand extreme forces. They are also more durable than variable resistance potentiometers because they do not contact with surfaces and reciprocate motion.
These sensors operate by applying a resonant frequency to the probe. This frequency is affected when the probe moves into or away from the hole of the hydraulic cylinder, and by measuring this change, we can determine the position of the probe relative to the hydraulic cylinder. This means that we know the position of the cylinder itself.
With the improvement of hydraulic system design and technology, new advantages continue to emerge, bringing benefits to engineers and designers. These three hydraulic cylinder position sensor technologies provide different methods for precise control of hydraulic cylinders. Considering the advantages and disadvantages of each technology and the requirements of the application, it is the system designer to determine which technology is the best choice.
