Basic knowledge of instrument
Detection and process control instrumentation (usually referred to as automated instrumentation) classification methods, according to different principles can be classified accordingly. For example, by using the meter energy classification, can be divided into pneumatic, electric and hydraulic instrument instrument instrument (rare); according to the instrument combination form, can be divided into base meter, unit combination instrument and integrated control device; the installation form according to the instrument, can be divided into field instrument, disc mounted instrument and frame install instrument; micro processor with good vigorous tuxedo, according to whether the introduction of instrument microprocessor (device) can be divided into intelligent instrument and intelligent instrument. According to the form of instrument signal can be divided into analog instruments and digital instruments.
According to the record and display instrument instructions, analog and digital functions, and can be divided into recording meter and instrument, analog instrument and digital display instrument, wherein the recording instruments can be divided into single point and multiple point records (record instructions can have a single point and multiple point), and one in the paper record or not if the paper records, paper records and record and print the record.
The regulating instrument is divided into a base type regulating instrument and a unit combined regulating instrument. Because of the introduction of the microprocessor, the programmable controller and the fixed program controller.
The actuator consists of two parts: actuator and control valve. According to the energy division, pneumatic actuators, electric actuators and hydraulic actuators can be divided into membrane type, piston type (cylinder type) and long stroke actuator. The valve according to the structure characteristics and flow characteristics of different puff are classified according to the structure characteristics of usually through single seat, through two seater, three pass, angular, diaphragm, butterfly valve, eccentric rotation, sleeve (cage), body separation, according to the flow characteristics into the line, on the number (such as than, parabola, quick opening etc.).
This kind of classification method is relatively reasonable, the instrument is also more extensive coverage, but any kind of classification methods are not all will be arranged to divide the instrument well in an orderly manner, their mutual penetration, communicate with each other. For example, the transmitter has a variety of functions, the temperature transmitter can be placed under the temperature measuring instrument, differential pressure transmitter can be placed under the flow meter, pressure transmitter can be placed under the pressure measuring instrument, if the over pressure method of measuring liquid level can be placed under the level measuring instrument, it is difficult to exactly under what kind of computing and auxiliary unit, foreign unit in the instrument cluster is difficult to merge.
