The displacement sensor is system equipment which is mainly used to measure the mechanical displacement in process industry.
The displacement sensor output can be divided into analog and digital signal, the magnetic liquid level switch and magnetic proximity switch input on-off signal, LVDT displacement output voltage or current signal, which is the typical analog signal, in addition, the analog signals include pulse signals, resistance and the millivolt signal, etc.; except analog signals, the LVDT displacement sensor can output the digital signal, such as RTU or ASCII format Modbus signal, digital signal output can be used in the limit position feedback of valve, unit operation and fault signal, analog signal is divided into active and passive two kinds.
If labeled the digital and analog signal in the coordinates, the digital signal is the discrete point in the coordinate system, and the analog signal is just one line.
The characteristics of the analog signal is relatively simple in structure, is to measure the displacement variation of the output is converted into digital directly read, general complex digital signal output, advantage is that the accuracy of measurement is relatively high, more accurately measuring the displacement variation. The specific strengths and weaknesses are as follows:
1. The analog signal is the physical quantity of continuous change over time, and the digital isn’t the quantity of continuous change over time.
2. The anti-interference ability of digital quantity is strong, and the analog quantity is weak.
3. The digital expression data is more accurate than the analog, but the data processing speed is not as fast as analog quantity, and the storage space is also large.4, Analog data expression is limited within a certain range, limited by the power supply, such as 5 v power supply, general analog can't more than 5 v, and digital quantity restricted by digits, only can increase infinite digits, wide range of expression, also can express the imaginary analog such as hard to express.