What's the difference between an electric meter and an instrument?

1, [electricity measuring instrument]: the general name of electrical instruments, used to measure voltage, current, electric power, etc.

2. [Electric kWh Meter]: Specifically, it is an watt-hour meter.

The abbreviation of watt-hour meter is used to measure electric energy, also known as watt-hour meter, fire meter, watt-hour meter and watt-hour meter.

Refers to an instrument for measuring various electric quantities.

galvanometer

electricity meter

Also known as "ammeter".

-An ammeter is a tool for measuring the current in a circuit.

-In the circuit diagram, the symbol of ammeter is "circle A"

The structure of DC ammeter mainly includes: three terminals [with "+"and "-"terminals, such as (+,-0.6, -3) or (-0.6, 3)], pointer, scale, etc. (AC ammeter has no positive and negative poles).

Usage rules of ammeter: ① ammeter should be connected in series in the circuit (otherwise it will be short-circuited. );

(2) Current flows from the "+"terminal and from the "-"terminal (otherwise the pointer is reversed. );

(3) The measured current should not exceed the range of the ammeter (you can touch it to see if it is out of range. );

(4) It is absolutely forbidden to connect the ammeter to the two poles of the power supply without using electrical appliances (the internal resistance of the ammeter is very small, which is equivalent to a wire. If the ammeter is connected to the two poles of the power supply, the pointer will be crooked, and the ammeter, power supply and wires will burn out. ).

-ammeter reading: 1. See the range clearly

2. Look at the division value clearly (generally speaking, the division value of 0~3A is 0. 1A, 0~0.6A, and 0 ~ 0.6a is 0.02A).

3. See clearly where the hand stays (be sure to look from the front)

-Preparation before use: 1. Zero calibration, adjust the zero calibration button with a screwdriver.

2. Select the measuring range (estimated by experience or trial touch method)

-Working principle: The ammeter is made according to the action of the magnetic field force in the magnetic field on the charged conductor.

There is a permanent magnet inside the ammeter, which generates a magnetic field between the two poles. In the magnetic field, there is a coil with a hairspring at both ends. Each spring is connected to a terminal of an ammeter, and the spring and the coil are connected through a rotating shaft. There is a pointer at the front end of the rotating shaft relative to the ammeter.

When a current passes through, the current passes through the magnetic field along the spring and the rotating shaft, and the current cuts the magnetic induction line, so the coil deflects under the action of the magnetic field force, driving the rotating shaft and the pointer to deflect.

Because the magnitude of magnetic field force increases with the increase of current, the magnitude of current can be observed by the deflection degree of pointer.

This is called magnetoelectric ammeter, which is the kind we usually use in the laboratory.

Attachment: AC ammeter

Ac ammeter can be directly used for small current (generally below 5A), but now the electrical equipment in the factory has a large capacity, so it is often used in conjunction with current transformer. Calculate the rated working current of the equipment before choosing the ammeter, then choose the appropriate current transformer and then choose the ammeter. For example, the equipment is a 30KW motor, and the rated current is about 60A, so we should choose a 75/5A current transformer and an ammeter with the range of 0A-75A and 75/5A, which is a choice of ammeter for high-current equipment!

A voltmeter is an instrument for measuring voltage.

1) common voltmeter-voltmeter symbol: v

2) Most voltmeters are divided into two ranges. (0—3V)(0— 15V)

3) Correct use: zero adjustment (adjust the pointer to zero scale), parallel connection (only connected with the measured part in parallel), positive input and negative output (making the current flow in from the positive electrode and out from the negative electrode) range (the measured voltage cannot exceed the range of the voltmeter), and select the appropriate range by "trial touch" method.

4) a _ should be added to the symbol of 4)DC voltmeter under V, and wavy line "~" should be added to the symbol of AC voltmeter under V.

The voltmeter has three terminals, a negative terminal and two positive terminals.

For example, a voltmeter used by students generally has two positive terminals, namely 3V, 15V. When the measuring range is "15V" according to the voltage, each large cell on the dial represents 5V and each small cell represents 0.5V (that is, the minimum voltage division value is 0.5V). When the measuring range is "3 Ⅴ", each large cell on the dial represents lV and each small cell represents 0.lV (that is, the minimum division value is 0.l Ⅴ).

We can measure the current with an ammeter. The symbol of ammeter is (A).

Ac voltmeter is divided into positive electrode and negative electrode. Select the range correctly and connect the voltmeter directly in parallel at both ends of the circuit under test.

The voltage measured by AC voltmeter is the effective value of AC voltage.

Voltage characteristics of series and parallel circuits

The voltage across the series circuit is equal to the sum of the voltages of all parts of the circuit, and U=U 1+U2.

In the parallel circuit, the voltages at both ends of each branch are equal, and U=U 1=U2.

Voltmeter principle

First, we need to know that there is a magnet and a coil in the voltmeter. When the coil is energized, it will generate a magnetic field (this content seems to be beyond the scope of your current study, but you must know the electromagnet), so that when the coil is energized, it will rotate under the action of the magnet, which is the meter head part of ammeter and voltmeter.

The current that this meter can pass is very small, and the voltage that both ends can bear is also very small (definitely much less than 1V, maybe only a few volts or even less). In order to measure the voltage in our actual circuit, we need to connect a relatively large resistor in series with this voltmeter to make it a voltmeter. In this way, even if a relatively large voltage is applied at both ends, most of the voltage acts on the large resistor we add, and the voltage on the meter will be very small.

It can be seen that voltmeter is a kind of instrument with great internal resistance, which should generally be greater than several thousand ohms.

An ammeter is made according to the action of magnetic field force on a charged conductor in a magnetic field.

There is a permanent magnet inside the ammeter, which generates a magnetic field between the two poles. In the magnetic field, there is a coil with a hairspring at both ends. Each spring is connected to a terminal of an ammeter, and the spring and the coil are connected through a rotating shaft. There is a pointer at the front end of the rotating shaft relative to the ammeter.

When a current passes through, the current passes through the magnetic field along the spring and the rotating shaft, and the current cuts the magnetic induction line, so the coil deflects under the action of the magnetic field force, driving the rotating shaft and the pointer to deflect.

Because the magnitude of magnetic field force increases with the increase of current, the magnitude of current can be observed by the deflection degree of pointer.

This is called magnetoelectric ammeter, which is the kind we usually use in the laboratory.

An ammeter is connected in series with a large resistor. When measuring, parallel connection between the two points to be measured will not change the characteristics of the original circuit. The displayed value of ammeter is proportional to the voltage at the measuring point:

The internal resistance Ro of ammeter is very small, which can be ignored, and the external resistance r is very large. According to ohm's law, it is concluded that:

The internal resistance of ideal ammeter is 0; The internal resistance of an ideal voltmeter is infinite.

I = U/(R + Ro) ≈ U/R

DA30A true rms voltmeter

Performance characteristics:

True effective value measurement

Various waveform voltages and random noise voltages can be measured.

Thermocouple detection mode, linear indication

Measuring frequency range: 10 Hz-10 MHz.

Large mirror instrument indicates clear reading.

The output of the DC amplifier can drive other auxiliary equipment.

Introduction:

DA30A true rms voltmeter is mainly used to measure the rms of various signal waveforms. Thermocouple detection mode is adopted, the instrument indication is linear scale, and zero adjustment is not needed, and DC output device is added to drive DC digital voltmeter to improve the measurement accuracy. Can be widely used in factories, laboratories, scientific research units, colleges and universities.

Technical parameters:

The frequency response range is 10 Hz- 10 MHz.

Basic accuracy 2%

Input resistance, capacitance, overload voltage 1mv-300mv: ≥ 8mω, ≤ 40pf, ≤ 100v.

300mV—300V:≥8mω，≤ 20 pF，≤600 V

DC output voltage-1 V (each 10 range)

General technical index

Working temperature, humidity 0℃-40℃, relative humidity ≤ 90%.

The power supply requirements are 198V-242V AC, 47.5Hz-52.5Hz.

Power consumption ≤ 6VA

Size (width× height× depth) 240mm×140mm× 280mm

Weighing about 2.5 kilograms.

Voltage, current and power are three basic parameters to characterize the energy of electrical signals. In electronic circuits, as long as one of the parameters is measured, the other two parameters can be obtained according to the impedance of the circuit. Considering the convenience, safety, accuracy and other factors, voltage measurement is almost always used to measure three basic parameters representing the energy of electrical signals. In addition, many parameters, such as frequency characteristics, harmonic distortion and modulation degree, can be regarded as derivatives of voltage. Therefore, voltage measurement is the basis of many other electrical parameters, including non-electrical measurement.

Voltage measurement mainly uses electronic voltmeter to measure the steady-state value of sinusoidal voltage and other typical periodic non-sinusoidal voltage parameters. This chapter focuses on the structure, principle and usage of analog voltmeter and digital voltmeter.

(1) Wide frequency range

The frequency of the measured signal voltage can change from 0Hz to several gigahertz, which requires that the frequency band of the signal voltage measuring instrument should cover a wide frequency range.

(2) Wide measuring voltage range

Usually, the measured signal voltage is as small as microvolts and as large as kilovolts. This requires that the measuring range of the voltage measuring instrument is quite wide. The lower limit that the voltmeter can measure is defined as the sensitivity of the voltmeter. At present, only digital voltmeter can achieve microvolt sensitivity.

(3) High input impedance

The input impedance of the voltage measuring instrument is an additional parallel load of the circuit under test. In order to reduce the influence of the voltmeter on the measurement results, it is required that the input impedance of the voltmeter is very high, that is, the input resistance is large and the input capacitance is small, so that the additional parallel load has little influence on the tested circuit.

(4) high measurement accuracy

General engineering measurement, such as the measurement of commercial power and the measurement of circuit power supply voltage, does not require high accuracy. However, the measurement of some special voltages does require high measurement accuracy. For example, the measurement of reference voltage of A/D converter and the measurement of voltage adjustment coefficient of regulated power supply all need high measurement accuracy.

(5) Strong anti-interference ability

The measurement work is generally carried out in the presence of interference, so the measuring instrument is required to have strong anti-interference ability. Especially for instruments with high sensitivity and precision, they must have strong anti-interference ability, otherwise obvious measurement errors will be introduced and the requirements of measurement accuracy will not be met. For digital voltmeter, this requirement is more prominent.

4. 1.2 classification of electronic voltmeter

Voltmeters are divided into analog voltmeter and digital voltmeter according to working principle and reading mode.

(1) analog voltmeter

Analog voltmeter, also known as pointer voltmeter, generally uses magnetoelectric DC ammeter head as the indicator of measured voltage. When measuring DC voltage, it can be converted into a certain amount of DC current directly or after amplification or attenuation to drive the pointer deflection indication of DC meter. When measuring AC voltage, it is necessary to convert the measured AC voltage into proportional DC voltage through an AC -DC converter, that is, a detector, and then measure the DC voltage. Analog voltmeter can be divided into the following types in different ways:

① Classification by working frequency: divided into ultra-low frequency (below 1kHz), low frequency (below 1MHz), video (below 30MHz), high frequency or radio frequency (below 300MHz) and ultra-high frequency (above 300MHz) voltmeters.

② According to the measured voltage, it can be divided into voltmeter (basic range is V) and millivoltmeter (basic range is mV).

③ Classification according to detection methods: average voltmeter, rms voltmeter and peak voltmeter.

④ According to the circuit composition, it is divided into detection-amplification voltmeter, amplification-detection voltmeter and heterodyne voltage.

electric energy meter

Definition: Watt-hour meter is an instrument used to measure electric energy, commonly known as watt-hour meter and fire meter.

Classification:

By use: industrial and civil electric meters, electronic standard meters, maximum demand meters, complex rate meters.

According to the structure and working principle: inductive (mechanical), electrostatic (electronic), mechatronics (hybrid)

According to the nature of power supply: AC meter and DC meter.

According to accuracy grade: common tables: 0.2S, 0.5S, 0.2, 0.5, 1.0, 2.0, etc.

Standard table: 0.0 1, 0.05, 0.2, 0.5, etc.

According to the installation and wiring mode: direct access and indirect access.

Electrical equipment: single-phase, three-phase three-wire and three-phase four-wire watt-hour meters.

Name and model of nameplate: Part 1 Part: Category code: D: electric energy meter

Part II: Group Code:

Initial s: three-phase three-wire T: three-phase four-wire X: reactive power B: standard Z: maximum demand D: single phase.

The second letter F: multi-rate table S: full electronic D: multifunctional Y: prepaid.

Part III: Design serial number: Arabic numerals

The fourth part: improved serial number: expressed by lowercase Chinese phonetic alphabet.

Part V: Derived number T: damp-heat dry-heat dual purpose TH: damp-heat zone G: plateau H: universal F: chemical corrosion protection; K: switchboard j: pulse watt-hour meter with receiver

Also marked with the symbol ① or ②, ① indicates that the accuracy of the electric energy meter is 1%, or 1 level meter; (2) The accuracy of the representative watt-hour meter is 2%, or 2 meters.

Also marked with the standard code, manufacturer, trademark and factory number of the product.

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appear

Hanyu pinyin: musical instrument yíbi?o

English explanation:

1. [Appearance; Appearance]: a person's appearance

2. [Instrument]: Various measuring instruments

The difference between musical instruments and musical instruments

Instrument is a machine in the sense of combination; It usually contains at least several instruments.

Instruments are generally only used to indicate data.

Instrument type:

1。 thermometer

Glass rod thermometer

bimetal thermometer

Pressure thermometer

thermocouple

thermal resistance

Non-contact thermometer

Temperature controller (regulator)

temperature sensor

Temperature calibration instrument

temperature sensor

Temperature mirror reflector

2。 Pressure instrument

pressure gage

pressure gage

pressure transmitter

differential pressure transmitter

Pressure calibration instrument

reliever

Tire barometer

Air pressure automatic adjustment controller

Hydraulic automatic adjustment controller

pressure transducer

3。 flowmeter

flowmeter

flow sensor

Flow transmitter

water meter

Gas cylinder

liquid level transmitter

Liquid level relay

liquid level indicator

oil meter

fluviograph

liquid level controller

Measuring instrument

4。 Electrical instruments and meters

galvanometer

voltmeter

Current power frequency meter

current distribution

Test pen

circuit breaker

change

Current contactor

relay

terminal

regulator

Voltage monitor

Intelligent power supply monitor

Regulator

megohmmeter

clip on ammeter

multimeter

Electric quantity transmitter

Current sensor

ballast

Selenium rectifier

5。 electronic measuring instrument

LCR measuring instrument

level meter

viscosimeter

oscilloscope

signal generator

6。 analytical instrument

Chromatographic instrument

Chromatographic fittings

photometer

Moisture measuring instrument

balance

Thermal analysis instrument

Ray analysis instrument

spectrometer

Physical characteristic analyzer

Photographic instrument

spectrum analyzer

7。 optical instrument

photometer

refractometer

color filter

Prism lens

spectrometer

chromatography

Photoelectric and laser instruments

microscope

telescope

amplifier

theodolite

water level

spectrograph

8。 Industrial process measurement and control instruments

control system

control valve

Regulating instrument

Multifunctional instrument

Heating equipment

hoister

equipment

intelligent instrument

safety barrier

Frequency converter/inverter

package

Paperless recorder

survey

amplifier

Acceleration sensor

Speed sensor

Displacement sensor

revolution speed transducer

Current sensor

tension pick up

9。 Laboratory instrument

Tian Ping instrument

Constant temperature experimental equipment

Vacuum measuring instrument

calorimeter

incubator

incubator

Corrosion testing room

hardmeter

drying furnace

oven

converter

Agitator

centrifuge

Water (oil) bath pot

Constant temperature water tank

10。 Measuring tool

measure

vernier calipers

micrometer

tape measure

dial gauge

1 1。 measure

Roundness meter measurement

Coordinate measuring machine

air pressure gauge

12。 actuating mechanism

electric operator

Pneumatic transmission device

13。 Special power supply for instrument

Dc power supply

Regulated power supply

alternating-current main

Switching power supply

UPS

transverter

14。 Indicating instrument

digital display

15。 Supply instruments

counter

electricity meter

thermostat

barostat

Meter reading system

counting device

16。 Universal experimental instrument

Electric heating plate

Electric jacket

Homogenizer

distiller

pharmacist

masher

17。 Mechanical quantity instrument

Thickness gauge

altitude gauge

dynamometer

Speed measuring instrument

18。 weighing apparatus

Quantitative scale

Platform scale/balance

railroad track scale

Pricing scale

weighing cell

electronic balance

Ground scale

belt scale

Hanging scale

Batch scale

19。 Industry professional test instrument

Wind speed, temperature and air volume measuring instrument

Temperature and humidity meter

Dust measuring instrument

noise measuring instrument

Water quality analysis and testing instrument

Acidimeter /PH meter

Conductivity meter

Polarographic recorder

Embroidery sample

gas analyzer

Illumination photometer

sound level meter

the dust particle counter

Grain and oil detection instrument

Mercury watt-hour meter

20。 testing equipment

tension tester

compression tester

bending tester

Series torsion testing machine

Impact testing machine

Universal testing machine

proof box

Nonmetallic material testing machine

Balance testing machine

nondestructive testing instrument

Process tester

Force and deformation detector

Automobile test equipment

Packaging tester

fatigue machine

strength-testing machine

laboratory

Platform vibrator

Main performance indexes of the instrument

I. Overview

In engineering, instrument performance indicators are usually described by accuracy (also called precision), variation and sensitivity. Instrument workers usually calibrate instruments by adjusting accuracy, variation and sensitivity. Variation refers to the maximum difference between the indicated values of the instrument when the measured variable (which can be understood as input signal) reaches the same value for many times from different directions, or the inconsistency between the measured parameter from small to large (positive characteristic) and the measured parameter from large to small (negative characteristic) when the external conditions of the instrument remain unchanged. The difference between them is called instrument deterioration, as shown in figure 1- 1. Change the percentage of the ratio of the maximum absolute error to the calibration range of the instrument:

The main reasons for the deterioration are the clearance of instrument power mechanism, the friction of moving parts and the lag of elastic elements. Thanks to the continuous progress of instrument manufacturing technology, especially the introduction of microelectronics technology, many instruments are all electronic and have no moving parts, and analog instruments have become digital instruments, so the index of variation is not so important and prominent in intelligent instruments.

Sensitivity refers to the sensitivity of the instrument to the change of measured parameters, or the ability to respond to the change of measured parameters, which is the ratio of the increment of output change to the increment of input change in steady state:

Sensitivity, sometimes called "magnification", is also the slope of each point on the static characteristic fitting line of the instrument. Increasing the magnification can improve the sensitivity of the instrument. Simply improving the sensitivity can not change the basic performance of the instrument, that is, the accuracy of the instrument has not improved. On the contrary, oscillation sometimes occurs, which leads to unstable output. The sensitivity of the instrument should be kept at an appropriate level.

But for instrument users, such as instrument workers in chemical enterprises, the accuracy of instruments is of course an important indicator, but in practical use, the stability and reliability of instruments are often emphasized, because there are not many instruments used for detection and process control in chemical enterprises, but a large number of them are used for testing. In addition, the stability and reliability of detection instruments used in process control system are more important than accuracy.

Second, accuracy.

Instrument accuracy is called accuracy, also called accuracy. Accuracy and error can be said to be twin brothers, because there is error, there is the concept of accuracy. In short, the accuracy of instrument is the accuracy that the measured value of instrument is close to the true value, which is usually expressed by relative percentage error (also called relative reduction error). The relative percentage error formula is as follows:

( 1- 1-3)

Where δ refers to the relative percentage error in the detection process;

(upper scale limit-lower scale limit)-measuring range of the instrument;

δx- absolute error is the difference between the measured value of the measured parameter x 1 and the standard value of the measured parameter x0.

The so-called standard value is the value measured by a standard meter whose accuracy is 3~5 times higher than that of the measured instrument.

It can be seen from the formula (1- 1-3) that the accuracy of the instrument is not only related to the absolute error, but also related to the range of the instrument. The absolute error is large, the relative percentage error is large, and the instrument accuracy is low. If two instruments with the same absolute error have different ranges, the instrument with large range has relatively small percentage error and high accuracy. Accuracy is a very important quality index of instruments, which is often standardized and expressed by accuracy grade. The accuracy level is the maximum relative percentage error minus the sign and%. According to the unified national regulations, the grades are 0.005, 0.02, 0.05, 0. 1, 0.2, 0.35, 1.0, 1.5.

2.5, 4, etc. The accuracy grade of the instrument is generally marked on the instrument scale or signboard, such as 0.5. The smaller the number, the higher the accuracy of the instrument.

In order to improve the accuracy of the instrument, it is necessary to carry out error analysis. Errors can usually be divided into negligence errors, slowly varying errors, systematic errors and random errors. Neglect error refers to the human error in the measurement process, one of which can be overcome and the other has nothing to do with the instrument itself. Progressive error is caused by the aging process of internal components of the instrument, which can be overcome and eliminated by replacing components or constantly correcting them. Systematic error refers to the error that occurs when the same measured parameter is repeatedly measured for many times, with the same size or sign, or changes according to a certain law. However, it is caused by accidental factors that people have not yet realized, and its size and nature are not fixed, so it is difficult to estimate, but its influence on the test results can be estimated theoretically through statistical methods. The sources of errors mainly refer to systematic errors and random errors. When the accuracy is expressed by error, it refers to the sum of random error and systematic error.

Third, reproducibility (repeatability)

Measurement repeatability is the degree of consistency of measurement results under different measurement conditions, such as different methods, different observers and different detection environments. Measurement repeatability will surely become an important performance index of the instrument.

The accuracy of measurement is not only the accuracy of the instrument, but also the influence of various factors on the measurement parameters, which is a comprehensive error. Taking the electronic type Ⅲ differential pressure transmitter as an example, the comprehensive error is shown in the following formula:

( 1- 1-4)

Where E0-(25 1)℃

E 1—— influence of ambient temperature on zero point (4mA),1.75%;

E2-the influence of ambient temperature on the full range (20mA), plus or minus 0.5%;

E3—— influence of working pressure on zero point (4mA), 0.25%;

E4—— influence of working pressure on full scale (20mA), plus or minus 0.25%;

Substituting the values of e0, e 1, e2, e3 and e4 into the formula (1- 1-4) gives:

This shows that due to the change of temperature and working pressure, the measurement accuracy of the 0.25-class electrical III transmitter has dropped from 0.25 to 1.87, which shows that the reproducibility of this instrument is poor. At the same time, it also shows that the measurement results are not consistent because of the different measurement conditions and the influence of environmental temperature and working pressure.

If the electronic type III differential pressure transmitter in the above example is replaced by a fully intelligent differential pressure transmitter, E0 = 0.0625%, E 1+E2 = 0.075% and E3+E4 = 0. 15 in the corresponding formula. It is far less than the E-synthesis of electric type ⅲ differential pressure transmitter = 1.87%, which shows that the fully intelligent differential pressure transmitter has strong temperature and pressure compensation ability and resistance to environmental temperature and working pressure. The anti-interference ability of the instrument can be described by the reproducibility of the instrument.

Measurement repeatability is usually estimated by uncertainty. Uncertainty is the degree of uncertainty about the measured value caused by the existence of measurement error, which can be expressed by variance or standard deviation (positive square root of Deng variance). All components of uncertainty fall into two categories:

Class A: Components determined by statistical methods.

Class B: Components determined by non-statistical methods.

Let the variance of Class A uncertainty be si2 (standard deviation is si) and the approximate variance of Class B uncertainty be ui2 (standard deviation is (ui)), then the combined uncertainty is:

( 1- 1-5)

Fourth, stability.

Within the specified working conditions, the ability of some performance of the instrument to remain unchanged with time is called stability (degree). Instrument stability is a performance index that instrument workers in chemical enterprises are very concerned about. Due to the harsh environment in which the instrument is used in chemical enterprises, the temperature and pressure of the measured medium change greatly. In this environment, the ability of some parts of the instrument to remain unchanged over time will be reduced, and the stability of the instrument will also be reduced. There is no quantitative value for measuring or characterizing the stability of instruments, and chemical enterprises usually use zero drift to measure the stability of instruments. The zero position did not drift within one year after the instrument was put into operation. On the contrary, the zero position of the instrument changed less than three months after it was put into operation, indicating that the stability of the instrument is not good. The stability of the instrument is directly related to the application scope of the instrument, and sometimes directly affects the chemical production. The influence caused by poor instrument stability is often greater than the influence caused by the decline of precision of double instruments. The poor stability and large maintenance of the instrument are the last things that instrument workers want to see.

Verb (abbreviation for verb) reliability

Instrument reliability is another important performance index pursued by instrument workers in chemical enterprises. Reliability and instrument maintenance are complementary. High instrument reliability means small instrument maintenance, while poor instrument reliability means large instrument maintenance. For the detection and process control instruments in chemical enterprises, most of them are installed on process pipelines, various towers, kettles, tanks and containers. Moreover, the continuity of chemical production and most toxic, flammable and explosive environments have added many difficulties to instrument maintenance. One is to consider the safety of chemical production, and the other is related to the personal safety of instrument maintenance personnel. Therefore, the use of detection and process control instruments in chemical enterprises requires as little maintenance as possible, that is, the reliability of the instruments is as high as possible.

With the upgrading of instruments, especially the introduction of microelectronic technology into instrument manufacturing industry, the indexability of instruments has been greatly improved. Instrument manufacturers pay more and more attention to this performance index, and usually use MTBF to describe the reliability of instruments. The MTBF of a fully intelligent transmitter is about 10 times higher than that of general non-intelligent instruments such as electric ⅲ transmitter, which can reach 100~390 years.

Market analysis:

The domestic market share of middle and low-grade electrical instruments and meters has reached 95%, and the domestic market share of high-grade products and the foreign market share of middle and low-grade products have been greatly improved on the existing basis. 20 10 China instrument industry market development is expected to improve. Product structure adjustment target. Among them, industrial automation instruments focus on the development of master control system devices and intelligent instruments based on fieldbus technology, special and special automation instruments. The technical level of products reached the advanced level of foreign countries in the late 1990s, and the sales in 2005 accounted for 30% of the domestic instrument sales. Facing the market, comprehensively expand the service field, promote the digitalization, intelligence and networking of instrument systems, and complete the transformation of automation instruments from analog technology to digital technology. By the end of the Tenth Five-Year Plan, the number of digital instruments will reach more than 60%.

The recruitment effect of electric meter talent network is average.