Magnetostrictive linear displacement / position transducers are sensors that operate using magnetostriction technology.
- Magnetostrictive position sensor working principle
- Eltra magnetostrictive linear transducers
- Eltra magnetostirctive distance sensors series
Magnetostrictive position sensor working principle
The physical phenomenon of magnetostriction is based on the following principle: when the magnetization of an object changes, its volume and linear dimensions also change.
The main parts of the magnetostrictive transducer are:
- Position magnet
- Ferromagnetic waveguide
- Strain pulse converter
- Damping zone
- Measurement electronics
Position magnet creates the first magnetic field in a waveguide. It occurs in a place where the slider is located. The magnetic field arises directly in the waveguide.
Ferromagnetic waveguide is the heart of the whole device. The pulse from a source moves to the current slider position through it. This pulse creates the second magnetic field.
Strain pulse converter receives a signal that moves from a positional magnet (from point of its location). The signal moves with the constant speed (ultrasonic). Hence, it is possible to determine the travel time of the signal and, therefore, the distance it has traveled.
Measurement electronics converts the received signal (its time, speed, distance) into a proportional output signal.
Damping zone damps or skips a signal directed to the opposite side of measuring head. This detail removes interference and the initial electrical pulse from source and does not allow its reflection from another side.
The main features of these sensors include non-linearity coefficient less than 0.02% and excellent repeatability of measurements up to 0.001%!
Eltra magnetostrictive linear transducers
Eltra s.p.a. produces the sensors with two types of output signals: SSI and analogue. All devices of this category are absolute sensors. They determine an absolute position of magnet. Thus, they do not require a starting point and can determine a position immediately after switching on.
Eltra Company produces the following series of magnetostrictive sensors:
Devices that use magnetostrictive principle have excellent resistance against mechanical stresses and shocks.
Eltra magnetostirctive distance sensors series
Let's look at all the series in detail.
It is a linear magnetostrictive transducer with an absolute position sensor and analogue interface.
It has 6 different types of outputs for working with one or two cursors:
- Standard (1 cursor) 0…10V DC
- Position/speed 1 cursor 0…10 V DC
- With min stroke 400 mm (2 cursors) 0…10 V DC
- Standard (1 cursor) 4…20 mA
- Position/speed (1 cursor) 4…20 mA
- stroke 400 mm (2 cursors) 4…20 mA
Cursors may move in distance between 50 and 1500 mm. Their maximum speed of movement reaches up to 10 m/s. The manufacturer produces two types of the cursors: sliding and floating. EMSPA series measures displacement and speed.
Its housing is made of anodized aluminum or Nylon 66 G 25 and has an enclosure rating of IP67. The device can operate at temperatures from -30 to 75 °C (-22 ... +167 °F).
Maximum resolution of the device is 16 bits. The coefficient of linear error is 0.02%.
This series is similar to the previous one. However, only two types of output signal are available here:
- 0,1…10,1 V DC 1 cursor (standard)
- 4…20 mA/1 cursor
Only single cursor variants are available. This type will be optimal when it needs to perform simple tasks. The stroke length reaches from 50 to 1500 mm at travel speed up to 10 m/s.
Such device only measures a cursor position. The devices are mounted axially using C4 (4 pin, DIN 43650-A) and M12 (5 pin) connectors. Its body is made of aluminum or nylon and has an IP65 level.
Its repeatability is less than 0.01 mm. Minimum linear error is equal to ± 0.04%. Its maximum resolution is infinite.
EMSPS is a series of linear magnetostrictive absolute sensors with digital RS-422 SSI compliant output. SSI interface (Synchronous Serial Interface) provides data using only two signals (clock and data). They are transmitted differentially via interface for digital data transmission RS422. This option allows increasing the distance for moving data.
The EMSPS converters have the following options of data length:
- 21+1 bit (FM357)
- 24 bit
- 25 bit
These devices operate with a resolution of 0.002 mm to 0.040 mm. Such transducers have a stroke of up to 1.5 m and travel speed of up to 10 m/s. Its case is made of identical materials, as in the previous series. The units operate at temperatures up to 90 °C (194 °F). For data transmission, binary and gray codes are used.
In addition to the main standard series, the company also produces special types of devices for direct installation (available in EMSSS and EMSSA series).
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