Debugging and installation of digital display instrument

Classification of detection and process control instruments (commonly referred to as automatic instruments) are diverse. According to different principles, corresponding classifications can be made. For example, based on the energy source used by the instrument, it can be classified into pneumatic instruments, electric instruments, and hydraulic instruments (rarely seen); according to the combination form of the instrument, it can be classified into stand-alone instruments, unit combination instruments, and comprehensive control devices; according to the installation form of the instrument, it can be classified into on-site instruments, panel-mounted instruments, and rack-mounted instruments; with the vigorous development of microprocessors, instruments can be further classified into smart instruments and non-smart instruments based on whether microprocessors are introduced. According to the form of the instrument signal, it can be classified into analog instruments and digital instruments.

Display instruments, based on functions such as recording and indication, analog and digital, can be classified into recording instruments and indicating instruments, analog instruments and digital display instruments. Among them, recording instruments can be further classified into single-point recording and multi-point recording (indication can also be single-point or multi-point), and there can be paper recording or non-paper recording, with paper recording further divided into chart recording and printing recording. Control instruments can be classified into stand-alone control instruments and unit combination control instruments. With the introduction of microprocessors, there is also a division between programmable controllers and fixed-program controllers.

Actuators consist of executive mechanisms and control valves. Executive mechanisms can be divided into pneumatic actuators, electric actuators, and hydraulic actuators based on energy sources, and can be classified into diaphragm type, piston type (cylinder type), and long stroke executive mechanisms based on structural form. Control valves can be classified according to their structural characteristics and flow characteristics. Common structural features include straight-through single-seated, straight-through double-seated, three-way, angle-type, diaphragm, butterfly, ball valves, eccentric rotating, cage (cage type), valve body separation, etc. Flow characteristics can be classified into linear, logarithmic (equal percentage), parabolic, quick opening, etc.

This type of classification method is relatively reasonable, and the coverage of instruments is relatively wide. However, no single classification method can neatly categorize all instruments, as there is overlap and communication among them. For example, transmitters have multiple functions. Temperature transmitters can be classified as temperature detection instruments, differential pressure transmitters can be classified as flow detection instruments, pressure transmitters can be classified as pressure detection instruments, and if used for level measurement, it can be classified as level detection instruments. It is difficult to clearly assign them to a specific category, and it's also challenging to merge the calculation and auxiliary units in standalone combination instruments.