First, the classification of displacement sensors
1, according to the sports classification:
Linear displacement sensor
Angle displacement sensor
2, according to the material classification:
Metal film sensor, conductive plastic sensor, photoelectric sensor, magnetic sensitive sensor, metal glass uranium sensor, winding sensor
Second, the main characteristic parameters
Nominal resistance: The resistance marked on the potentiometer above.
Repeat accuracy: The smaller this parameter, the better.
Resolution: The minimum displacement value that the displacement sensor can feedback. The smaller this parameter is, the better. The resolution of the conductive plastic displacement sensor is infinite.
Permissible error: The deviation of the ratio of the difference between the nominal resistance and the actual resistance, as a percentage of the nominal resistance, indicates the accuracy of the potentiometer. Allowable error is generally as long as
Within ±20%, it meets the requirements, because the general displacement sensor is used in partial pressure, and the size of the specific resistance has no effect on the data acquisition of the sensor.
Linear Accuracy: Linearity error. The smaller this parameter, the better.
Lifetime: Conductive plastic displacement sensors are more than 2 million times.
Third, the common sensor characteristics
Conductive plastic displacement sensor:
The DAP (diphenyl phthalate) resistor paste is coated on the insulating body by a special process, heated and polymerized into a resistive film, or a solid body formed by thermoplastically pressing the DAP resistance powder into the recess of the insulating matrix is ​​used as a solid body. Resistor body. Features are: good smoothness, excellent resistance to abrasion, long life, low noise, high reliability, chemical resistance. Used for the servo system of space devices, missiles, and aircraft radar antennas.
Wirewound displacement sensor: Connor wire or Nichrome wire is used as a resistor body, and it is made by winding it on the insulating skeleton. Winding potentiometer is characterized by small contact resistance, high precision and small temperature coefficient. Its disadvantages are poor resolution, low resistance and poor high frequency characteristics. Mainly used as a voltage divider, rheostat, instrument zero adjustment and work points.
Metal glass uranium displacement sensor:
Using a screen printing method according to a certain pattern, a metal glass uranium resistor paste is coated on a ceramic substrate and sintered at a high temperature. Features are: wide resistance range, good heat resistance, strong overload capacity, moisture resistance, wear resistance, etc.
It is a potent variety of potentiometers. The disadvantage is the large contact resistance and current noise.
Metal film displacement sensor:
The resistor body of the metal film potentiometer can be composed of an alloy film, a metal oxide film, a metal foil, and the like. Features are high resolution, high temperature resistance, small temperature coefficient, small dynamic noise, and good smoothness.
Magnetically sensitive displacement sensor:
Eliminate mechanical contact, long life, high reliability, shortcomings: high requirements on the working environment.
Photoelectric displacement sensor:
Eliminate mechanical contact, long life, high reliability, shortcomings: digital signal output, processing complicated.