Electricity meter diànbiǎo
1. [meter for measuring electricity]: A general term for electrical instruments, used to measure voltage, current, electric power, etc.
2. [electric kilowaterhour meter]: specifically refers to an electric meter
The abbreviation of electric energy meter is an instrument used to measure electric energy, also known as electric meter, fire meter, electric energy meter, and kilowatt-hour meter
Refers to instruments that measure various electrical quantities.
Ammeter
ammeter
Also known as "ampmeter".
--An ammeter is a tool for measuring the current in a circuit
--In the circuit diagram, the symbol of the ammeter is "circle A"
--DC ammeter The structure mainly includes: three binding posts [with "+" and "-" binding posts, such as (+,-0.6,-3) or (-,0.6,3)], pointer, scale, etc. (AC ammeter No positive and negative terminals)
--Rules for using ammeters:: ① The ammeter must be connected in series in the circuit (otherwise it will be short-circuited.);
②The current must flow from the "+" terminal In, come out from the "-" terminal (otherwise the pointer will reverse.);
③The measured current should not exceed the range of the ammeter (you can use the test touch method to see if it exceeds the range.);
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④ It is absolutely not allowed 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, equivalent to a wire. If the ammeter is connected to the two poles of the power supply, the pointer may become distorted. , or it may burn out the ammeter, power supply, and wires).
--Ammeter reading: 1. See the range clearly. 2. See the graduation value clearly (generally speaking, the range The graduation value of 0~3A is 0.1A, and the graduation value of 0~0.6A is 0.02A)
3. See clearly the position where the hands stay (must be observed from the front)
-- Before use Preparation: 1. Zero calibration, use a flat-mouth screwdriver to adjust the zero calibration button.
2. Select the measuring range {use experience to estimate or use the trial touch method}
--Working principle: The ammeter is based on A current-carrying conductor is made by the force of a magnetic field in a magnetic field.
There is a permanent magnet inside the ammeter, which generates a magnetic field between the poles. There is a coil in the magnetic field. There is a hairspring spring at each end of the coil. Each spring is connected to a terminal of the ammeter. Between the spring and the coil, there is a hairspring. A rotating shaft is connected, and at the front end of the rotating shaft relative to the ammeter, there is a pointer.
When there is current passing through, the current passes through the magnetic field along the spring and the rotating shaft, and the current cuts the magnetic induction lines, so it is affected by the magnetic field force, causing the coil to deflect, driving the rotating shaft and pointer to deflect.
Since the magnitude of the magnetic field force increases with the increase of the current, the magnitude of the current can be observed through the degree of deflection of the pointer.
This is called a magnetoelectric ammeter, which is the kind we usually use in the laboratory.
Attachment: AC ammeter
AC ammeter can be used directly in small currents (generally below 5A), but the capacity of current factory electrical equipment is large, so most of them are related to current. used together with transformers. Before choosing an ammeter, you must calculate the rated operating current of the equipment, then select a suitable current transformer, and then select an ammeter. For example: the equipment is a 30KW motor, the rated current is about 60A, so we need to choose a 75/5A current transformer, then the ammeter must choose an ammeter with a range of 0A-75A, 75/5A, so it is a large current Selection of ammeter for equipment!
A voltmeter is an instrument for measuring voltage
1) Commonly used 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 (can only be connected in parallel with the part being measured) positive in and negative out (make the current flow from The positive electrode is connected to flow in, and the negative electrode is connected to flow out) range (the measured voltage cannot exceed the range of the voltmeter, use the "test touch" method to select the appropriate range.
4) The symbol of the DC voltmeter should be added with a _ under V, and the symbol of the AC voltmeter should be added with a wavy line "~" under V
The voltmeter has three connections. terminal, one negative terminal and two positive terminals
For example, a student voltmeter generally has two positive terminals, 3V and 15V. When measuring, select the range "15V" according to the voltage. Each large grid on the dial represents 5V, and each small grid represents 0.5V (that is, the minimum graduation value is 0.5V); when the measuring range is "3V", each large grid on the dial represents lV, and each small grid represents 0.lV (that is, the minimum graduation value is 0.lV).
We can use an ammeter to measure the magnitude of the current. The symbol of the ammeter is (A).
The AC voltmeter does not distinguish between positive and negative poles. Select the correct range and directly connect the voltmeter in parallel to both ends of the circuit under test.
The voltage measured by the AC voltmeter is the effective value of the AC voltage.
Voltage characteristics of series and parallel circuits
The voltage at both ends of the series circuit is equal to the sum of the voltages at both ends of each part of the circuit, U=U1+U2
Parallel circuit , the voltage at both ends of each branch is equal, U=U1=U2
Principle of voltmeter
First of all, we need to know that inside the voltmeter, there is a magnet and a wire coil , after passing the current, the coil will generate a magnetic field (it seems that this content is beyond what you have learned so far. It will be learned in the second semester of the second grade of junior high school, but you must know about electromagnets). In this way, after the coil is energized, under the action of the magnet It will rotate. This is the head part of the ammeter and voltmeter.
The current that this meter can pass is very small, and the voltage that both ends can withstand is also very small (certainly much less than 1V, maybe only a few tenths of a volt or even less). In order to measure our For the voltage in the actual circuit, we need to connect a relatively large resistor in series with the voltmeter to make a voltmeter. In this way, even if a relatively large voltage is applied to both ends, most of the voltage will act on the large resistor we added, and the voltage on the meter will be very small.
It can be seen that the voltmeter is an instrument with a large internal resistance, which should generally be greater than several thousand ohms.
The ammeter is made according to the magnetic field force exerted by the current-carrying conductor in the magnetic field.
There is a permanent magnet inside the ammeter, which generates a magnetic field between the poles. There is a coil in the magnetic field. There is a hairspring spring at each end of the coil. Each spring is connected to a terminal of the ammeter. Between the spring and the coil, there is a hairspring. A rotating shaft is connected, and at the front end of the rotating shaft relative to the ammeter, there is a pointer.
When there is current passing through, the current passes through the magnetic field along the spring and the rotating shaft, and the current cuts the magnetic induction lines, so it is affected by the force of the magnetic field, causing the coil to deflect, driving the rotating shaft and pointer to deflect.
Since the magnitude of the magnetic field force increases with the increase of the current, the magnitude of the current can be observed through the degree of deflection of the pointer.
This is called a magnetoelectric ammeter, which is the kind we usually use in the laboratory.
A large resistor is connected in series with the ammeter.
When measuring, connecting it in parallel between the two points being measured will not change the characteristics of the original circuit. The value displayed by the ammeter is proportional to the voltage of the measured point:
The internal resistance Ro of the ammeter is very small and can be ignored. The external resistance R is very large, which is obtained according to Ohm's law:
The internal resistance of an ammeter in an ideal state is 0; the internal resistance of a voltmeter in an ideal state is infinite
I = U/( R + Ro) ≈ U/R
DA30A true RMS voltmeter
Performance characteristics:
True RMS measurement
Can measure various waveform voltages and irregular noise voltages
Thermocouple detection method, linear indication
Measuring frequency range: 10 Hz — 10 MHz
Large mirror Meter indication, clear reading
DC amplifier output, can drive other auxiliary equipment
Brief introduction:::
DA30A true RMS voltmeter is mainly used The effective value of various signal waveforms is measured using thermocouple detection. The instrument indication has a linear scale and does not require zero adjustment. It is also equipped with a DC output device to drive a DC digital voltmeter to improve measurement accuracy. It can be widely used in factories, laboratories, scientific research units, colleges and universities, etc.
Technical parameters:
Frequency response range 10 Hz — 10 MHz
Basic accuracy ± 2%
Input resistance, capacitance, overload Voltage 1 mV — 300 mV: ≥8 MΩ, ≤ 40 pF, ≤100 V
300 mV — 300 V: ≥8 MΩ, ≤ 20 pF, ≤600 V
DC Output voltage -1 V (every 10 range)
General technical indicators
Operating temperature, humidity 0℃ — 40℃, ≤90% RH
Power supply requirements 198 V — 242 V AC, 47.5 Hz — 52.5 Hz
Power consumption ≤ 6 VA
Dimensions (W×H×D) 240 mm×140 mm×280 mm
Weight is about 2.5 kg
Voltage, current, and power are the three basic parameters that characterize the energy of electrical signals. In electronic circuits, as long as one parameter is measured, the other two parameters can be calculated based on the impedance of the circuit. Considering the convenience, safety, accuracy and other factors of measurement, the method of measuring voltage is almost always used to measure the three basic parameters that characterize the energy of electrical signals. In addition, many parameters, such as frequency characteristics, harmonic distortion, modulation, etc., can be regarded as derived quantities of voltage. Therefore, the measurement of voltage is the basis for many other electrical parameters, including non-electricity measurements.
Voltage measurement mainly uses electronic voltmeters 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 use of analog and digital voltmeters.
(1) Wide frequency range
The frequency of the measured signal voltage can vary from 0Hz to several gigahertz, which requires the frequency band of the signal voltage measuring instrument to cover a wider range. Wide frequency range.
(2) Wide measurement voltage range
Usually, the measured signal voltage ranges from microvolts to more than kilovolts. This requires the measuring range of the voltage measuring instrument to be quite wide. The lower limit that a voltmeter can measure is defined as the sensitivity of the voltmeter. Currently, only digital voltmeters can reach microvolt level 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, the input impedance of the voltmeter is required to be very high, that is, the input resistance is large and the input capacitance is small, so that the additional parallel load has little impact on the circuit under test.
(4) High measurement accuracy
General engineering measurements, such as measurement of mains power and measurement of circuit power supply voltage, do not require high accuracy. However, the measurement of some special voltages does require high measurement accuracy.
For example, the measurement of the reference voltage of the A/D converter and the measurement of the voltage regulation coefficient of the regulated power supply require high measurement accuracy.
(5) Strong anti-interference ability
Measurement work is generally performed in an environment with interference, so measuring instruments are required to have strong anti-interference ability. In particular, high-sensitivity and high-precision instruments must have strong anti-interference capabilities, otherwise significant measurement errors will be introduced and the measurement accuracy requirements will not be met. For digital voltmeters, this requirement is even more prominent.
4.1.2 Classification of electronic voltmeters
Voltmeters are divided into two categories: analog voltmeters and digital voltmeters according to their working principles and reading methods.
(1) Analog voltmeter
Analog voltmeter is also called pointer voltmeter. It generally uses a magnetoelectric DC ammeter as an indicator of the measured voltage. When measuring DC voltage, it can be directly or amplified or attenuated into a certain amount of DC current to drive the pointer deflection indication of the DC meter. When measuring AC voltage, it is necessary to convert the measured AC voltage into a proportional DC voltage through an AC-DC converter, that is, a detector, and then measure the DC voltage. Analog voltmeters are divided into the following types according to different methods:
① Classified by working frequency: divided into ultra-low frequency (below 1kHz), low frequency (below 1MHz), video (below 30MHz), High frequency or radio frequency (below 300MHz), ultra high frequency (above 300MHz) voltmeter.
② Classification according to the measured voltage level: divided into voltmeters (the basic range is V level) and millivolt meters (the basic range is mV level).
③Classification according to detection method: divided into average voltmeter, effective value voltmeter and peak voltmeter.
④ Classification according to circuit composition: divided into detection-amplification voltmeter, amplification-detection voltmeter, and heterodyne voltage.
Electric energy meter
Definition: An electric energy meter is an instrument used to measure electrical energy, commonly known as an electric meter or a fire meter.
Classification:
By use: industrial and civil meters, electronic standard meters, maximum demand meters, multiple rate meters
According to structure and working principle: Inductive (mechanical), static (electronic), electromechanical (hybrid)
According to the nature of the power supply: AC meter, DC meter
According to the accuracy level: Commonly used ordinary meters: 0.2S, 0.5S, 0.2, 0.5, 1.0, 2.0, etc.
Standard meters: 0.01, 0.05, 0.2, 0.5, etc.
According to the installation and wiring method: direct connection Type, indirect access type
According to electrical equipment: single-phase, three-phase three-wire, three-phase four-wire energy meter
Nameplate name and model: Part 1: Category code: D: Electric energy meter
Part 2: Group code:
First letter S: three-phase three-wire T: three-phase four-wire X: reactive power B: standard Z: highest Demand D: Single-phase
Second letter F: Composite rate schedule S: Fully electronic D: Multi-function Y: Prepaid
Part 3: Design serial number: Arabia Numbers
Part 4: Improved serial number: represented by lowercase Chinese Pinyin letters
Part 5: Derivative number T: for both wet and dry heat TH: for wet and tropical areas G: For plateau use H: For general use F: For chemical anti-corrosion; K: Switch plate type J: Pulse electric energy meter with receiver
It is also marked with ① or ②, ① means the accuracy of the electric energy meter is 1 %, or called a level 1 meter; ② represents the accuracy of the electric energy meter is 2%, or called a level 2 meter.
It is also marked with the standard code used by the product, manufacturer, trademark and factory number, etc.
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Instrument
Chinese Pinyin: Instrument yíbiǎo
English explanation:
1. [appearance; bearing looks]: person’s appearance
2. [meter]: various measuring instruments
Meter The difference with instruments
An instrument is a combined machine; it usually contains at least several instruments.
Instruments are generally only used to indicate data
< p> Types of instruments:1. Temperature instrument
Glass thermometer
Bimetal thermometer
Pressure thermometer
Thermocouple
Thermal resistance< /p>
Non-contact thermometer
Temperature control (regulator)
Temperature transmitter
Temperature calibration instrument
< p> Temperature sensorTemperature tester
2. Pressure instrument
Pressure gauge
Pressure gauge
Pressure transmitter
Differential pressure transmitter
Pressure calibration instrument
Pressure reducer
Tire pressure gauge
Automatic air pressure adjustment control instrument
Hydraulic automatic adjustment control instrument
p>Pressure sensor
3. Flow meter
Flow meter
Flow sensor
Flow transmitter
Water meter
Gas meter
p>Liquid level transmitter
Liquid level relay
Liquid level gauge
Oil meter
Water level gauge
p>Liquid level controller
Metering instrument
4. Electrical Instruments
Ammeter
Voltmeter
Current power frequency meter
Current distribution
Electrical test pen< /p>
Circuit breaker
Switch
Contactor
Relay
Terminal block
Adjustment Voltage regulator
Voltage monitor
Intelligent power monitor
Voltage regulator
Megger
Clamp meter
Multimeter
Electricity transmitter
Current transmitter
Ballast
Rectifier
5. Electronic measuring instruments
LCR measuring instrument
Level meter
Viscometer
Oscilloscope
Signal generator
6. Analytical instruments
Chromatograph
Chromatography accessories
Photometer
Moisture meter
Balance
Thermal analysis instruments
Ray analysis instruments
Spectrometers
Physical property analysis instruments
Photographic instruments
p>Spectrum Analyzer
7.
Optical instruments
Photometer
Refractometer
Filter, color filter
Prism, lens
Spectrometer
Colorimeter
Optoelectronics, laser instruments
Microscope
Telescope
Magnifying glass
Theodolite
Level
Spectrometer
8. Industrial automation instruments
Control systems
Regulating valves
Regulating instruments
Multifunctional instruments
Heating equipment< /p>
Winding machine
Device
Intelligent instrument
Safety barrier
Frequency converter
Module
Paperless recorder
Probe
Amplifier
Acceleration sensor
Speed ??sensor
Displacement sensor
Speed ??sensor
Current sensor
Tension sensor
9. Experimental instruments
Balance instruments
Constant temperature experimental equipment
Vacuum measuring instruments
Calorimeter
Incubator< /p>
Thermostatic oven
Corrosion test chamber
Hardness tester
Drying oven
Oven
Oscillator
Stirrer
Centrifuge
Water (oil) bath
Constant temperature water tank
10. Measuring Tools
Gauge
Vernier Caliper
Micrometer
Tape Measure
Dial Indicator
11. Measuring instrument
Roundness meter
Three-dimensional coordinate measuring machine
Pneumatic measuring instrument
12. Actuator
Electric actuator
Pneumatic actuator
13. Special power supply for instruments
DC power supply
Stabilized power supply
AC power supply
Switching power supply
Uninterruptible power supply
Inverter power supply
14. Display instrument
Digital display instrument
15. Supply of application instruments
Counters
Electricity meters
Thermostats
Voltage regulators
Meter reading systems
Counter
16. General experimental instruments
Electric hot plate
Electric heating mantle
Homogenizer
Distiller
Disperser< /p>
Masher
17. Mechanical measuring instruments
Thickness gauge
Altimeter
Force measuring instrument
Speed ??measuring instrument
18. Weighing instruments
Quantitative scales
Bench scales
Rail scales
Pricing scales
Load cells
< p> Electronic scaleFloor scale
Belt scale
Crane scale
Ingredients scale
19.
Industry professional testing instruments
Wind speed, temperature and air volume meter
Temperature and humidity meter
Dust meter
Noise meter
< p> Water quality analysis and testing instrumentsAcidity meter/PH meter
Conductivity meter
Polarograph
Sampler
Gas analysis instruments
Illuminance meters
Sound level meters
Dust particle counters
Grain and oil detection instruments
Mercury meter
20. Testing equipment
Tensile testing machine
Compression testing machine
Bending testing machine
Torsion testing machine
Impact Testing machine
Universal testing machine
Test chamber
Non-metallic material testing machine
Balancing machine
Non-destructive Testing instruments
Process testing machine
Force and deformation detector
Automobile testing equipment
Packaging testing machine
< p> Fatigue testing machineStrength testing machine
Test room
Vibration table
Main performance indicators of the instrument
1. Overview
In engineering terms, instrument performance indicators are usually described by accuracy (also known as 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 of the instrument (which can be understood as the input signal) reaches the same value from different directions multiple times, or it is the measured value of the instrument when the external conditions remain unchanged. The degree to which the parameter changes from small to large (forward characteristics) and the measured parameter changes from large to small (reverse characteristics) are inconsistent. The difference between the two is the instrument variation, as shown in Figure 1-1-1. The variation size is calculated as the percentage of the ratio of the maximum absolute error to the scale range of the instrument:
The main causes of variation are the clearance of the vibrating mechanism of the instrument, the friction of moving parts, the hysteresis of elastic elements, etc. With the continuous improvement of instrument manufacturing technology, especially the introduction of microelectronics technology, many instruments have become fully electronic with no moving parts, analog instruments have been changed to digital instruments, etc., so the indicator of variation is not obvious in smart instruments. So important and prominent.
Sensitivity refers to the sensitivity of the instrument to changes in the measured parameter, or its ability to respond to changes in the measured quantity. It is the ratio of the increment of output change to the increment of input change under steady state. :
Sensitivity is sometimes called "amplification ratio", which is also the slope of each point on the line where the static characteristics of the instrument fit. Increasing the amplification factor can improve the sensitivity of the instrument. Simply increasing the sensitivity does not change the basic performance of the instrument, that is, the accuracy of the instrument is not improved. On the contrary, oscillation may sometimes occur, causing the output to be unstable. Meter sensitivity should be maintained at an appropriate amount.
However, for instrument users, such as instrument workers in chemical companies, instrument accuracy is certainly an important indicator, but in actual use, more emphasis is often placed on the stability and reliability of the instrument, because chemical company testing and A small number of process control instruments are used for measurement, while a large number are used for detection. In addition, the stability and reliability of detection instruments used in process control systems are more important than accuracy.
2. Accuracy
Instrument accuracy is technically called precision, also known as accuracy. Accuracy and error can be said to be twin brothers. Because of the existence of error, the concept of accuracy exists. In short, instrument accuracy is the accuracy of the instrument measurement value close to the true value, usually expressed as relative percentage error (also called relative conversion error). The relative percentage error formula is as follows:
(1-1-3)
In the formula, δ - relative percentage error during the detection process;
(on the scale Limit value - lower limit of the scale) - measuring range of the instrument;
Δx - absolute error, which is the difference between the measured value x1 of the measured parameter and the standard value x0 of the measured parameter.
The so-called standard value is the value measured by a standard meter that is 3 to 5 times more accurate than the instrument being tested.
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 measurement range of the instrument. If the absolute error is large, the relative percentage error will be large, and the instrument accuracy will be low. If two instruments with the same absolute error have different measurement ranges, then the instrument with a larger measurement range will have a smaller relative percentage error and a higher instrument accuracy. Accuracy is a very important quality indicator of an instrument and is often standardized and represented by accuracy levels. The accuracy level is the maximum relative percentage error minus the sign and %. The grades divided according to unified national regulations include 0.005, 0.02, 0.05, 0.1, 0.2, 0.35, 1.0, 1.5, 2.5, 4, etc. The instrument accuracy grade is generally marked on the instrument scale or sign, such as , ,0.5, etc. The smaller the number, the higher the accuracy of the instrument.
To improve the accuracy of the instrument, it is necessary to conduct error analysis. Errors can generally be divided into omission errors, slowly changing errors, systematic errors and random errors. Negligent errors refer to errors caused by humans during the measurement process. First, they can be overcome. Second, they have nothing to do with the instrument itself. The slow-varying error is caused by the aging process of the internal components of the instrument. It can be overcome and eliminated by replacing components, parts or through continuous correction. Systematic error refers to the error in which the numerical size or sign is the same when the same measured parameter is measured repeatedly, or the error changes according to a certain rule. It can be caused by accidental factors that have not yet been recognized by people. Its numerical value The size and nature are not fixed and difficult to estimate, but its impact on the detection results can be theoretically estimated through statistical methods. The sources of errors mainly refer to systematic errors and random errors. When error is used to express accuracy, it refers to the sum of random errors and systematic errors.
3. Reproducibility (repeatability)
Measurement reproducibility refers to the measurement results under different measurement conditions, such as different methods, different observers, and different testing environments. The extent to which the measurement results are consistent when testing the same measured quantity. Measurement reproducibility will definitely become an important performance indicator of instruments.
The accuracy of measurement is not only the accuracy of the instrument, but also includes the influence of various factors on the measurement parameters, which is the comprehensive error. Taking the electric type III differential pressure transmitter as an example, the comprehensive error is as follows:
(1-1-4)
In the formula, e0-(25±1)℃ Reference accuracy under normal conditions, ±0.25% or ±0.5%;
e1-The impact of ambient temperature on zero point (4mA), ±1.75%;
e2--The impact of ambient temperature on zero point (4mA) The influence of full scale (20mA), ±0.5%;
e3-The influence of working pressure on zero point (4mA), ±0.25%;
e4--The influence of working pressure on Influence of full scale (20mA), ±0.25%;
Substituting the values ??of e0, e1, e2, e3, and e4 into equation (1-1-4), we get:
This It shows that the measurement accuracy of the 0.25-level electric III transmitter dropped from the original 0.25 level to 1.87 due to changes in temperature and working pressure, indicating that the reproducibility of this instrument is poor. It also shows that when the same measured quantity is detected, due to the measurement The conditions are different and affected by the ambient temperature and working pressure, the measurement results are less consistent.
If a fully intelligent differential pressure transmitter is used to replace the electric type III differential pressure transmitter in the above example, Correspondingly, e0=±0.0625%, e1+e2=±0.075%, e3+e4=±0.15% in the corresponding formula (1-1-4), and substituted into the formula (1-1-4), we get e=±0.18%, It is much smaller than the electric type III differential pressure transmitter e comprehensive = ±1.87%, which shows that the fully intelligent differential pressure transmitter has strong ability to compensate for temperature and pressure and withstand ambient temperature and working pressure. Instrument reproducibility can be used to describe the instrument's anti-interference ability.
Measurement reproducibility is usually estimated in terms of uncertainty. Uncertainty is the degree to which the measured value cannot be certain due to the existence of measurement errors. It can be expressed by variance or standard deviation (the positive square root of the variance).
All components of uncertainty are divided into two categories:
Category A: components determined using statistical methods
Category B: components determined using non-statistical methods
Suppose the variance of type A uncertainty is si2 (standard deviation is si), and the corresponding approximate variance assumed to exist for type B uncertainty is ui2 (standard deviation is (ui), then the synthetic uncertainty is:
(1-1-5)
4. Stability
Within specified working conditions, the ability of certain performance of an instrument to remain unchanged over time is called stability ( Degree). Instrument stability is a performance indicator that instrument engineers in chemical companies are very concerned about. Since the environment in which chemical companies use instruments is relatively harsh, the temperature and pressure of the medium being measured also changes relatively greatly. Therefore, the instrument is put into use in this environment. , the ability of some parts of the instrument to remain unchanged over time will decrease, and the stability of the instrument will decrease. There is no quantitative value to characterize the stability of the instrument. Chemical companies usually use zero drift of the instrument to measure the stability of the instrument. There is no drift in the zero position within one year of operation. On the contrary, the zero position of the instrument changes within less than 3 months of operation, indicating that the stability of the instrument is directly related to the scope of use of the instrument. Sometimes. Directly affecting chemical production, poor instrument stability often has a greater impact on chemical production. Poor instrument stability also requires heavy instrument maintenance, which is the last thing that instrument workers want.
5. Reliability
Instrument reliability is another important performance indicator pursued by instrument engineers in chemical companies. Reliability and instrument maintenance are inversely related to each other. High instrument reliability indicates instrument maintenance. On the other hand, the reliability of the instrument is poor, and the maintenance of the instrument is large. For chemical industry testing and process control instruments, most of them are installed on process pipelines, various towers, kettles, tanks, and vessels, and most of them are toxic in order to maintain the continuity of chemical production. , flammable and explosive environments. These harsh conditions add a lot of 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, chemical companies use detection and process control instruments to require less maintenance. The better, that is to say, the reliability of the instrument is required to be as high as possible.
With the upgrading of instruments, especially the introduction of microelectronic technology into the instrument manufacturing industry, the instrument manufacturers' reportability has been greatly improved. Performance indicators are also paying more and more attention. The reliability of the instrument is usually described by the mean time between failures (MTBF). The MTBF of a fully intelligent transmitter is about 10 times higher than that of a general non-intelligent instrument such as an electric III transmitter. It can As high as 100 to 390 years.
Market analysis:
The domestic market share of mid- and low-end electrical instrumentation products reaches 95%, and the domestic market share of high-end products is as high as that of mid- and low-end products. Foreign market share has increased significantly based on the current situation. The market development of my country's instrument industry is expected to increase in 2010. Among them, industrial automation instruments focus on the development of main control system devices and intelligent instruments based on fieldbus technology, as well as special and dedicated automation instruments. The product technology level has reached the advanced foreign level in the late 1990s, and sales in 2005 accounted for 30% of domestic instrument sales. Facing the market, we will comprehensively expand our service areas, promote the digitization, intelligence, and networking of instrument systems, and complete the transformation of automated instruments from analog technology to digital technology. By the end of the "Tenth Five-Year Plan", the number of digital instrument varieties will reach more than 60%.
The recruitment effect of the Electric Meter Talent Network is average