Commonly Used Terms of Valves (Part One)

The instrument is responsible for the measurement, monitoring and control of the whole factory, and tells us the operation of each device all the time. The instrument and control post guarantee the normal operation of the factory. Do you know the following 227 terms of automation instrument and control system?
 
1. Measuring point (primary point)
 
It refers to the point in the detection system or control system that is directly in contact with the process medium. Such as the pressure taking point in the pressure detection system, the thermocouple and thermal resistance installation point in the temperature detection system, etc. The secondary point can be on the processing pipeline or on the process equipment.
 
2. Primary component (source component)
 
It refers to the processed parts of instruments usually installed at the primary point, such as the pressure nipple in the pressure detection system and the thermometer boss in the temperature measurement system.
 
3. Primary valve (pressure valve)

It refers to the valves installed on the primary components, such as the valves of the pressure detection system connected to the pressure tap, the valves connected to the outlet pipes of the positive and negative pressure chambers of the orifice plate, etc.
 
4. Primary element (sensor)
 
It refers to the components installed on the site and in contact with the process medium, such as thermocouples and thermal resistors.
 
5. Primary instrument
 
A kind of on-site instrument refers to instruments installed on the site and directly in contact with the process medium, such as a spring tube pressure gauge, bimetal thermometer, differential pressure transmitter, etc.
 
6. Primary calibration (single calibration)
 
It refers to the calibration of instruments before installation. According to the requirements of the Code for Construction and Acceptance of Industrial Automation Instrument Engineering (GBJ-86), in principle, each instrument should be calibrated once. The focus of calibration is to check the indication error and variation of the instrument, and to adjust the proportional band, the error of integration time and differential time, the deviation of control points, and the balance degree of the instrument. Only instruments whose primary calibration meets the requirements of design or product specifications can be installed to ensure the quality of the secondary calibration.
 
7. Secondary instrument
 
It refers to the general name of all kinds of instruments whose value signals are not directly in contact with the process media. The input signal of the secondary instrument is usually the standard signal converted by the transmitter. There are generally three kinds of standard signals accepted by secondary instruments: pneumatic signals; Type II electric unit combination instrument signals; HI electric unit combination instrument signals.
 
8. Field instruments
 
It refers to the general name of instruments installed on the site, including all primary instruments and secondary instruments installed on the site.
 
9. Secondary calibration (secondary joint school and system calibration)
 
It refers to the inspection of the whole detection circuit or automatic control system after the on-site installation of the instrument, and after the wiring of the control room is completed and verified. It is also a comprehensive verification before the instrument is delivered for official use. The calibration method is usually to add a signal in the detection link, and then carefully observe whether each instrument of the system works within the allowable error range. If the error is beyond the allowable range, and the reason cannot be found, it is necessary to re-debug all the instruments that make up the system.
 
10. Processed parts of instruments
 
It refers to the general name of all metal and plastic machined parts used for instrument installation, which occupies a special position in instrument installation.
 
11. Flow chart with control points
 
It refers to the drawings that describe the automation content of the production process with the design symbols of the process detection and control system.
It marks the installation position of the instrument in detail, is an important drawing to determine the primary point, is a comprehensive embodiment of the automatic control scheme and automation level, and is also the basis of automatic control design, and can be used as a reference for construction, installation and production operation. 　
 
12. Common instruments and control graphic symbols
 
According to the national industry standard HG20505—92 "Characters and symbols for process detection and control system", which refers to the national standard GB2625—81, common graphs and characters for chemical automatic control are as follows.
 
Graphic Symbol
 

1. The measuring point (including the detection element) is the starting point of the connecting lead from the process equipment or pipeline symbol to the instrument circle, and there is generally no specific graphic symbol.

2. If the measuring point is located in the equipment, when it is necessary to mark the position of the measuring point in the process equipment, a small circle symbol with a diameter of 2mm or a dotted line can be added at the starting point of the lead.

3. The graphic symbol of connecting line. The connecting lead between the instrument circle and process measurement point. The symbols of the general instrument signal line and energy line are thin solid lines. When it is necessary to mark the energy category, the corresponding abbreviation can be used to keep the energy line symbol. For example, AS-014 is an air source of 0.14MPa, and ES-24DC is a DC power supply of 24 V.

4. When the general instrument signal line is a thin solid line, which may cause confusion, the general signal line symbol can be added with an oblique dash line (the oblique dash line makes an angle of 45 with the thin solid line).

1. Automatic instruments
 
It is also known as process detection and control instrument, the general name of the instruments that detect, display, control and execute industrial processes.
 
2. Detection element sensor, sensor element sensor
 
It refers to the primary element in the measurement chain, which converts input variables into signals suitable for measurement.
 
3. Sensor
 
It refers to a device that receives information formed by physical or chemical variables (input variables) and converts it into output variables of the same kind or another kind according to certain rules.
 
Note: According to the nature of the physical phenomenon on which the sensor is based, there are many measuring sensors with different forms and names, such as temperature sensor, pressure sensor and flow sensor.
 
4. Transmitter
 
It refers to a measuring sensor that outputs a standardized signal. For example temperature transmitter, pressure transmitter, flow transmitter, etc.
 
5. Compensator, compensation element
 
It refers to a device designed to counteract the error source caused by changing specified working conditions.
 
6. Meter, gauge
 
It refers to a device for measuring and indicating the measured value.
 
Note: Meters (meters) can only be used with modifiers, such as flowmeter and pressure gauge.
 
7. Indicator
 
It refers to a device that provides a visual indication of the measured variable.
 
8. Recorder
 
It refers to a device for recording the related value of its input signal.
 
9. Multi-point recorder
 
It refers to a recorder that records each input signal with a series of printing symbols by a printing mechanism.
 
10. Trend recorder
 
It refers to a standardized signal recorder according to the compiled program or selected by the operator for the common use of multiple variables.
 
11. Differentialamplifier
 
It refers to an amplifier with two similar input lines, which can respond to the difference between two voltages or two currents after being connected to each other.
 
12. Operational amplifier
 
It refers to a differential amplifier with high gain, high input impedance and low output impedance.
 
13. Isolatedamplifier

There is no point-connected amplifier between the input line and the output line and between the two lines and the ground.
 
14. Totalizinginstrument of total meter
 
A measuring instrument that determines the measured value by summing the values of each part of the measured quantity. These partial values can be obtained from one or more sources simultaneously or sequentially.
 
15. Computing device computing device
 
A device or function that can perform one or more calculations and/or logical operations and output one or more calculated signals.
 
16. Feedback controller feedback controller
 
A device that can work automatically and change the controlled variable by comparing the controlled variable value with the reference variable value, thereby reducing the difference between them.
 
17. Signal selector
 
Means for selecting the desired signal from two or more input signals.
 
18. Automatic/manual operator
 
A device that can be switched between automatic control and manual control by process operators and manually control one or more terminal control elements.
 
19. Manual operator
 
A device that has only manual operation output and is used to operate one or more remote instruments.
 
20. Alarm unit alarm unit
 
A device with audible and/or visual output to indicate that the equipment or control system is abnormal or out of the limit.
 
21. (measurable) quantity
 
Attributes of a phenomenon, object or substance that can be qualitatively distinguished and quantitatively determined.
 
22. Variable
 
A variable and usually measurable quantity or state.
 
23. (Measurement) unit (of measurement)
 
In order to quantitatively represent the quantity with the same dimension, a specific quantity is agreed to be selected.
 
24. (Measurement) system of units (of measurement)
 
A set of units is established for a given quantitative system. For Example, the International System of Units (SI); Cg system of units. Note: The unit system includes a set of selected basic units and derived units determined by definition equations and scale factors.
 
25. (Quantity) value (of a quantity)
 
A quantity is expressed in a number and an appropriate unit of measurement. For example: 5.3m; 12kg; -40℃.
 
26. True value
 
It strictly defines the assumed theoretical values of variables.
 
Note 1. The true value of the quantity is an ideal concept, usually unknown.
2. What is actually used is the so-called "agreed truth value".
 
27. The agreed truth value (conventional true value)
 
For a certain purpose, the magnitude of the true value can be replaced.
 
Note: Generally speaking, the agreed truth value is considered to be very close to the truth value, and the difference can be neglected for certain applications.
 
28. Measurement
 
A set of operations for the purpose of determining the magnitude.
 
29. Static measurement
 
Measurement of a quantity whose value can be regarded as constant during the measurement.
 
Note: The word "static" is applicable to the measured, but not to the measuring method.
 
30. Dynamic measurement
 
Measurement of the instantaneous value or the change value with the time of (variable) quantity.
 
Note: The word "dynamic" applies to the measured, not to the measuring method.
 
31. Measured measurand, measured quantity
 
It refers to the measured quantity.
 
32. Measured variable
 
It refers to the quantity, characteristic, or state of being measured.
 
Note: The measured variables are usually temperature, pressure, flow rate, speed, etc.
 
33. Input variable
 
It refers to the input variables to the meter.
 
34. Output variable
 
An output variable is a variable output by the instrument.
 
35. Measured value
 
It refers to the value according to the information acquired by the measuring device at a specified moment under specified conditions and expressed in numbers and measurement units.
 
36. Impact quantity
 
A quantity that is not measured but affects the measured value or the value indicated by the measuring instrument. For example ambient temperature, and frequency of measured AC voltage.
 
37. Signal
 
A physical variable in which one or several parameters carry information of one or more variables represented by a signal.
 
38. Measurement signal
 
A signal that is measured in a measurement system.
 
39. Analogue signal
 
It refers to the information parameters that can be expressed as signals of all values in a given range.
 
40. Digital signal
 
The information can be expressed as a signal of any value in a set of discrete values represented by numbers.
 
41. Standardized signal
 
Signals with standardized upper and lower range values.
 
For example: 4mA-20mA (d.c.), 20 kPa ~ 100kPa
 
42. The InPut signal
 
A signal is applied to the input of a device, element, or system.
 
43. Output signal
 
A signal is sent by a device, component or system.
 
44. Quantified signal
 
A signal with quantized information parameters.
 
45. Binary signal
 
A quantized signal with only two values.
 
46. Result of a measurement
 
The measured value is obtained by measuring.
 
Note 1. When the term "measurement result" is used, it should be clear whether it is an indication, an uncorrected result or a corrected result, and whether several observations have been averaged.
2. A complete description of the measurement results should include: information about measurement uncertainty and information about the corresponding impact value.
 
47. Indication (of a measuring instrument)
 
The measured value is provided by the measuring instrument.
 
48. Measurement accuracy
 
Synonym: Measurement accuracy refers to the degree of agreement between the measured measurement result and the (agreed) true value.
 
49. Measure repeatability
 
Under the same measuring method, the same observer, the same measuring instrument, the same place, the same working conditions and the repeated conditions in a short period of time, it refers to the consistency degree between the results obtained by continuous measurement of the same measured number of times.
 
50. Error
 
It refers to the algebraic difference between the measured value and the true value of the measured variable.
 
Note 1. When the measured value is greater than the true value, the error is positive.
2. When the error is listed on the data sheet of the instrument or device, the calibration method of the instrument or device must be specified.