【正文】 ly is the temperature on the accuracy, of course, must be higher than the ultrasonic, radar must use high resolution radar in the tank, without ultrasonic. As for the price, usually ultrasonic, lower than the radar in a wide range of course some ultrasonic price is also high. Such as the range of 670 meters, the preferred ultrasonic liquid level meter. Pay attention to the stirring groove, groove wall adhesion can produce interference of the reflected wave, level measurement, the installation is to choose the appropriate installation position, so as to avoid the interference of these factors. Level two categories, including liquid level and material level. Liquid level and liquid level indicator and two continuous level measurement. Liquid level indicator is the level of several fixed position measuring, used in liquid level of upper and lower limit alarm, etc. Continuous level measurement is to measure liquid level continuously, it is widely used in many fields such as petroleum, chemical industry, food processing, have very important significance. For more than 20 kinds of continuous level measurement method for parative analysis. Glass tube, glass plate, double color water method. Manual gauging glass tube method: this method is using the principle of municating vessels, level scale read directly from the instructions. Glass plate method: glass which can be 4 installed through connectors can also be installed in the container wall openings, and series a few piece of glass to increase the range. Numerical scale read directly from the glass plate level. Double color gauge method: this method using the optical principle, make water shows green, and make the water vapor shows red, which indicate the water level. Artificial gauging method: the method is used for measuring oil tank liquid level. When measuring, the surveyor gauge Surveyor to volume of the oil dipstick into oil, and filed when feet lead contact with the tank bottom oil dipstick. According to the quantity of oil traces on the oil dipstick, read out the oil level height。 H level. Differential pressure transmitter will pressure difference transformation for 4 ~ 20 mA dc signal. If the pressure in the measuring range lower limit of the corresponding output signal is greater than or less than 4 mA, are all need to adjust the migration zero migration technology such as spring, is equal to 4 mA. HTG method: this method is applied to differential pressure oil tank liquid level measurement. Buoy method: this method USES the middle maglev barrel with holes as liquid level sensor. Stainless steel casing from buoy hole through the middle, between fixed to the roof and bottom. Liquid level change driven maglev hollow tube (permanent mag) hides inside can move up and down the casing, and attract the casing of mag can move up and down the casing wall, secondary instrument | instrument according to the moving mag volume to calculate the liquid level. 5 Floating ball method: this method is using the lever principle of work. Floating ball with liquid level change and around the axis of rotation, the pointer on the drive shaft rotation, and at the other end of the lever balance weight balance, at the same time indicates the level value on the dial. Floating ball method have ball float within and outside the floating ball type two kinds. Floating ball method is mainly used for high temperature measurement, the viscosity of the liquid level, but the range is smaller. Servo method: this method USES volatile integral circuit, eliminate jitter, prolong life, improve the precision of level measurement. The modern servo liquid meter measuring accuracy is higher, has 40 m range less than the accuracy of 1 mm, and generally has the function of measuring density distribution and average density. Sinking method: the location of the sinking as the change of liquid level change, but the variation is not equal and level variation. Torque tube sinking method: the torque tube core shaft torsional Angle changes, secondary instrument according to the torsional Angle variation to calculate the liquid level above five kinds of methods are using the buoyancy principle to work. Such as R, R, l, is a fixed value, as long as the use of epsilon 1, epsilon 2, CH can calculate the liquid level H. Measurement of conductive liquid capacitance method princ