10 techniques for correctly selecting displacement sensors

　　Displacement sensor, also called linear sensor, is a linear device with metal induction. The function of sensor is to convert various measured physical quantities into electrical quantities. In the process of production, displacement measurement is generally divided into two kinds: measurement of physical size and mechanical displacement. According to the changing form of the measured variables, the displacement sensor can be divided into two types: analog and digital. The simulation model can be divided into two types: physical and structural. The commonly used displacement sensor to simulate the structure types, including potentiometer displacement sensor, inductance displacement sensor, synchro, capacitive displacement sensor, eddy current displacement sensor, Holzer type displacement sensor etc.. An important advantage of the digital displacement sensor is that it is convenient to send the signals directly into the computer system. This kind of sensor develops rapidly and is used more and more widely

　　Many enterprises in the Engineer for the selection of appropriate displacement sensor trouble, what kind of company, are in the budget control and cost, choose the displacement sensor is based on the reference factors what displacement sensor selection and specification parameters etc..

　　The purchaser of displacement sensor needs to understand the working principle of displacement sensor and the installation method of displacement sensor, so as to know how to select the type of displacement sensor. Displacement sensors, like other sensors, convert the amount of change seen in reality to electrical signals. According to the general displacement size and the needs of users to choose what precision sensor, considering its error, considering the application environment it the distance of corresponding users have influence on data acquisition. Similarly, the displacement sensor is a sensitive device, and the precautions needed to be used at the time of purchase make the sensor have a longer service life

　　Displacement sensor, as its name suggests, is a sensor that detects displacement changes. The physical change of displacement is converted into electrical signal output, and the displacement sensor is divided according to displacement object, angle and displacement

　　Linear displacement sensor, general sense of displacement sensor refers to the linear displacement sensor, here analysis refers to the linear displacement sensor, in accordance with the principle of the sensor, straight line

　　There are dozens of displacement sensors, listed here are some of the common: LVDT differential transformer displacement sensor, magnetostrictive displacement sensor, electronic ruler or potentiometer (resistance type)

　　Grating displacement sensor, ultrasonic displacement sensor, laser displacement sensor, capacitive displacement sensor, pull rope displacement sensor and so on.

　　The different occasions and different objects of the choice of what kind of sensor, which has the reference factors? Here I would have some Chaohui frequently asked questions for customers

　　Let's enumerate:

　　First, displacement range.

　　The range of travel refers to the maximum distance to be detected, which is the most direct reference factor. In general, the following 50mm is called a small scale, 50mm-3000

　　Mm is called a large scale, and over 3000mm is super large range.

　　The LVDT displacement sensor and resistance displacement sensor should be selected in a small range, and a large number of magnetostrictive displacement sensors, grating displacement sensors and pull rope displacement sensors should be selected in a large number of ways

　　Ware and so on.

　　Second 、 output signal.

　　Sensor output signals are conventional 4-20mA, 0-5V, 0-10V, RS485, wireless, and so on.

　　Third, linear error.

　　The displacement linearity, such as the stroke 1mm, and the linearity error is 0.25%, means that when the object is moved 1mm, the detection value is 1mm + 0.0025m

　　M.

　　Fourth, resolution.

　　Resolution is the ability of a sensor to sense the smallest changes to be measured. That is, if the amount of input varies slowly from a nonzero value. When input

　　When the change value does not exceed a certain value, the output of the sensor will not change, that is to say, the sensor can not tell the change of the input quantity. Only when the amount of input changes over points

　　The output changes only when the resolution rate is changed.

　　Fifth, repeatability accuracy.

　　Repeatability accuracy. The error of repeated detection at the same location is usually expressed as a percentage of ten thousand times, such as repetition accuracy of 0.01%FS.

　　Sixth, accuracy.

　　The degree of closeness between a calculated value or an estimate and its true value. As for accuracy, it needs to be explained here, because the term "precision" is interpreted in a conventional sense

　　The maximum error is the product of the linear error and the displacement range. For example, the stroke 1mm and the linearity error are 0.25%, then the accuracy is 0.0025mm, which is expressed as the true value 1mm

　　The detection value was 1 + 0.0025mm.

　　Many people confuse accuracy with repeatability, linearity, error, and resolution, which need to be distinguished. These parameters are different in meaning and influence each other, and the accuracy is not higher

　　The better, if the accuracy is higher than the resolution, the accuracy does not make any sense.

　　Now, many businesses in order to get customers favor, often in the "high-precision" concept on the article, or confusion, repeatability, precision, resolution concept, or hide the temperature drift coefficient, or

　　Correction of product coefficients.

　　Seventh, temperature drift.

　　Zero drift. The sensor work is affected by the outside temperature, and the change of the outside temperature has certain influence on the output of the sensor value. A product of high accuracy

　　Temperature drift coefficient must be low, otherwise the environmental temperature changes, the output value of the impact of the ratio of large, high precision becomes meaningless.

　　Eighth 、 sensor working environment. For example, the product is