I. Principle of ML33-RG high temperature resistant type eddy current displacement sensor:
Eddy current sensor systems work on the eddy current effect, which is an inductive measuring principle. The eddy current effect originates from the energy of an oscillating circuit. The eddy currents need to be formed in a conductive material. By introducing an alternating current into the coil inside the sensor probe, a magnetic field is formed around the probe coil. If a conductor is placed into this magnetic field, eddy currents are excited in the conductor according to Faraday's law of electromagnetic induction. According to Franz's law, the magnetic field of the eddy currents is in the opposite direction of the magnetic field of the coil, and this changes the impedance of the coil inside the probe. This change in impedance is directly related to the distance from the coil to the object being measured. After the sensor probe is connected to the controller, the controller can obtain the change in voltage value from the sensor probe and use this as a basis for calculating the corresponding distance value, the eddy current measurement principle can measure all conductive materials.
Since eddy currents can penetrate insulators, even metallic materials covered with insulators can be used as measurement objects for eddy current sensors. The unique coil winding design enables the sensor to operate in high-temperature measurement environments while maintaining a compact form factor.
2. ML33-RG high temperature resistant type eddy current displacement sensor application areas:By measuring the relative position of the metal body to be measured and the probe end, eddy current displacement sensor sensing and processing into the corresponding electrical signal output. The sensor can work reliably for a long time, high sensitivity, strong anti-interference ability, non-contact measurement, fast response speed is not subject to the influence of oil and water and other media, in the large-scale rotating machinery, such as shaft displacement, shaft vibration, shaft speed and other parameters of long-term real-time monitoring is widely used, and has been extended to the satellite launch, material identification, weighing measurement, metal plate thickness measurement, material deformation and other application areas.
3. ML33-RG high temperature resistant type eddy current displacement sensor technical parameters:
Measure range | 12.5mm | 20mm | 25mm | 40mm |
Probe diameter | Φ30mm | Φ40mm | Φ50mm | Φ60mm |
Linearity error | ≤±1%FS | ≤±1%FS | ≤±1%FS | ≤±2%FS |
Repeatability | 2um | 2～4um | 2～4um | 2～5um |
Frequency response | 0～100Hz | |||
Output signal | RS485 | |||
Resolution | 16bit | |||
Supply voltage | +9～36VDC | |||
Working current | ＜70mA | |||
Probe temperature compensation range | 0℃～+180℃ | |||
Temperature drift error | ≤±1mm | |||
Operating temperature | probe 0℃～+180℃，proximitor 0℃～+60℃ | |||
Protection grade | probe IP67，proximitor IP65 | |||
Probe cable | standard 2m，can be customized | |||
Feed cable | standard 2m，can be customized | |||
4.ML33-RG high temperature resistant type eddy current displacement sensor wiring:
The sensor has five contacts: positive power (brown), power ground (black), RS485A (blue), RS485B (white), and case ground (shielded).
5. ML33-RG high temperature resistant type eddy current displacement sensor installation dimensions:
The ML33 sensor system consists of probes, proximitor, cables, and accessories.
1. Eddy current probe:
Usually the probe consists of a coil, head, shell, high-frequency cable, high-frequency connector. In the production process, the probe head body is generally used in high temperature PPS engineering plastics, through the ‘secondary injection’ moulding will be sealed coil. So that the probe can work reliably in harsh environments. As the coil diameter of the head body to determine the linear range of the sensor system, so we usually use the external diameter of the head body to classify and characterise the various types of probes, in general, the linear range of the sensor system is roughly 1/2 to 1/4 times the diameter of the head of the probe.ML33 series sensors probes are shown in the table:
Range | Probe diameter | Probe length | shell length | Installation type | Thread specification |
12.5mm | Φ30mm | 26mm | 40mm | Reverse-mounting | M14X1.5 |
20mm | Φ40mm | 33mm | 40mm | Reverse-mounting | M14X1.5 |
25mm | Φ50mm | 42mm | 50mm | Reverse-mounting | M18X1.5 |
40mm | Φ60mm | 47mm | 50mm | Reverse-mounting | M18X1.5 |
Probe housings are used to connect and secure the probe head and are used as a clamping structure when the probe is mounted. The housings are generally made of 304 stainless steel with standard threads and locking nuts. In order to adapt to different applications and installations, probe housings are available in different forms and with different threads and dimensions.
2. Proximitor:
The proximitor is the signal processing centre of the whole sensor system. On the one hand, the preamplifier for the probe coil to provide high-frequency AC excitation current to make the probe work; on the other hand, the preamplifier through a special circuit senses the probe head body and the head body in front of the metal conductor of the gap changes, through the preamplifier processing, resulting in the gap with the linear changes in the output signal.
ML33-RG series proximitor outline dimensional drawing
Probe selection rulers
● A □□:Probe range code selection
▼ Probe code classification
Code | 12 | 20 | 25 | 40 |
Measuring range | 12.5mm | 20mm | 25mm | 40mm |
● B□□ :No thread length option
The threaded part of the probe is to facilitate installation, reduce invalid thread length, and make screwing bolts faster
▼Metric threaded probe
Minimum unthreaded length 0mm | 0 | 0 |
Maximum unthreaded length 250 mm | 2 | 5 |
Increase by 10 mm | 0 | 1 |
● C □□ Shell length selection
The length of the probe shell depends on the use of the site, in order to ensure the measurement accuracy, avoid the vibration of the probe rod to bring measurement interference, it is recommended not to use more than 300mm long shell length; When necessary, a mounting attachment for strengthening the probe rod should be attached.
▼Metric shell length
Minimum shell length 20mm | 0 | 2 |
Maximum shell length 250 mm | 2 | 5 |
Increase by 10 mm | 0 | 1 |
● C □□ Shell length selection
The length of the probe shell depends on the use of the site, in order to ensure the measurement accuracy, avoid the vibration of the probe rod to bring measurement interference, it is recommended not to use more than 300mm long shell length; When necessary, a mounting attachment for strengthening the probe rod should be attached.
▼Metric shell length
Minimum shell length 20mm | 0 | 2 |
Maximum shell length 250 mm | 2 | 5 |
Increase by 10 mm | 0 | 1 |
6. Installation and use:
Probe installation
□ Distance between each probe of the port □Distance between the port probe and the mounting surface
□Selection of mounting bracket □Mouth probe mounting clearance
□Installation of the cable with the probe □Sealing and insulation of the cable adapter of the port
□Corrosion resistance of the probe □High pressure environment of the probe
● Distance between probes
When the current is passed through the coil of the probe head, an alternating magnetic field will be generated around the head, so when installing the two probes, it should be noted that the installation distance between the two probes should not be too close, otherwise the two probes will interfere with each other through the magnetic field (as shown in the following figure of the distance between the probes), and the output signal iterated on the two probes of the differential signal, resulting in a distortion of the results of the measurements, which is a case we call the neighbourhood of the interference. Factors related to the elimination of neighbouring interference are: the shape of the measured body, the head diameter of the probes, and the mounting method. Typically, the * minimum distance between the probes is shown in the table below.