I would like to ask what the specific meanings of primary instruments and secondary instruments are

The instruments that perform measurement and transmission are primary instruments, while those that provide indication and control are secondary instruments

Primary instruments can be considered as the workers on the front line, while secondary instruments can be regarded as the workers in the back office. Primary instruments generally refer to those that come into direct contact with the measured medium, such as those for measuring temperature, pressure, flow rate, liquid level, tension, rotational speed, current, voltage, etc. They can usually be divided into two main categories: thermal instruments and electrical instruments. Secondary instruments are those used to display and record these process parameters, and they are collectively referred to as secondary instruments.

Primary instrument: refers to an instrument that is installed on-site and in direct contact with the process medium. Secondary instruments: These are a general term for various types of instruments whose indication signals do not come directly from the process medium. There are generally three types of standard signals received by secondary instruments: ① Pneumatic signal: 0.02~0.1 MPa; ② Type II electric unit instrument signal: 0~10 mA DC; ③ Type III electric unit instrument signal: 4~20 mA DC

I am extremely grateful for the help and guidance from all of you! ! I’ve learned a lot of new things; thank you so much! !

I majored in process engineering, and I would like to know here what the precise definitions and differences are between primary instruments and secondary instruments Thank you! Last edited by naska on 2008-3-27 10:07]

Primary instruments are those located at the site, while secondary instruments are those displayed on the gauges in the control room

Primary instruments should be field indication and measurement devices (such as pressure gauges, bimetallic thermometers, thermal resistors, etc.), while secondary instruments should be conversion devices and panel display devices (such as transmitters, digital displays, etc.)

You can check the mechanic’s manual; it’s available on the forum. http://www.rdlm.com.cn/bbs/viewthread.php?tid=53257&page=1 This post was last edited by *ejian109 on 2008-3-26 11:21]

Instruments installed during the manufacturing process are called primary instruments, such as those on pipes, containers, etc. Some others are designed to provide auxiliary functions for primary instruments, such as amplification, power supply, signal conversion, etc.; they are also considered primary instruments, for example orifice plates + differential pressure transmitters, pH electrodes + pH transmitters, etc.

Primary meters and secondary meters are old terms from the past. In general, primary meters refer to instruments located at the site, while secondary meters refer to those in the control room. At the site itself, primary meters are the measurement sensors that are directly attached to the pipes; secondary meters at the site refer to transmitters.

I don’t know what counts as one time and what counts as two times

A primary instrument is one of the components (elements) of an automatic detection device. It is equipped with sensing elements to detect changes in the parameters of the medium being measured. Or it may have a scale to indicate the reading ； Or it has no scale and does not indicate a reading on its own. In the production process, measuring instruments are often classified qualitatively based on the number of times of energy conversion: those that convert energy once are called primary instruments, while those that convert it twice are called secondary instruments. Taking temperature measurement with thermocouples as an example, the thermocouple itself converts thermal energy into electrical energy, which is why it is called a primary instrument. If the electrical energy is then converted into mechanical energy that causes a pointer to move, using a potentiometer (or millivoltmeter), this second conversion of energy results in what is known as a secondary instrument. When the number of conversions exceeds two, it is usually referred to as two conversions. For example, in flow measurement using orifice plates, the orifice plate itself is considered a primary instrument; the differential pressure transmitter has no specific designation, while the indicating instrument is called a secondary instrument, as it is used to indicate, record, or accumulate the measurement results from the primary instruments.

I work in the field of craftsmanship as well; I’m currently learning *.

Primary instruments come into direct or indirect contact with the medium being measured, such as bimetallic thermometers with probes, thermocouples, thermal resistors, transmitters with liquid-contact elements, level gauges, and so on； Secondary instruments are connected to the transduction output of primary instruments, such as digital meters and isolators.

Primary instrument: refers to an instrument that is installed on-site and in direct contact with the process medium. Secondary instruments: These are a general term for various types of instruments whose indication signals do not come directly from the process medium. There are generally three types of standard signals received by secondary instruments: ① Pneumatic signal: 0.02~0.1 MPa; ② Type II electric unit instrument signal: 0~10 mA DC; ③ Type III electric unit instrument signal: 4~20 mA DC

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