Tinko Instrument (Suzhou) Co., Ltd.

Introduction to the basic knowledge of ten types of transmitters

Number of visits: Date:2018-09-05

I. integrated temperature transmitter

The integrated temperature transmitter is generally composed of a temperature probe (thermocouple or thermal resistance) and a two-wire solid state electronic unit. The temperature measuring probe is directly installed in the junction box in the form of solid module, thus forming an integrated transmitter. Integrated temperature transmitter is generally divided into two types: thermal resistance and thermocouple.

Thermal resistance temperature transmitter is composed of reference unit, R/V conversion unit, linear circuit, reverse connection protection, current limiting protection, V/I conversion unit, etc. After the thermal resistance signal of temperature measurement is converted and amplified, the nonlinear relationship between temperature and resistance is compensated by the linear circuit. After the V/I conversion circuit, a 4-20ma constant current signal with a linear relationship with the temperature under test is output.

Thermocouple temperature transmitter is generally composed of reference source, cold end compensation, amplification unit, linearization processing, V/I conversion, couple breaking processing, reverse connection protection, current limiting protection and other circuit units. It amplifies the thermoelectric potential generated by thermocouple through cold end compensation, eliminates the nonlinear error between thermoelectric potential and temperature by linear circuit, and finally converts the amplification into the output signal of 4-20ma current. In order to prevent the thermocouple measurement due to the couple broken wire and temperature control failure caused by accident, the transmitter is also equipped with a power failure protection circuit. When the thermocouple breaks the wire or the contact is bad, the transmitter will output the maximum value (28mA) to make the meter cut off the power.

The integrated temperature transmitter has the advantages of simple structure, saving lead, large output signal, strong anti-interference ability, good linearity, simple display instrument, anti-seismic and moisture-proof solid module, reverse connection protection and current-limiting protection, reliable operation and so on.

The output of the integrated temperature transmitter is 4~20mA; It can be used in conjunction with microcomputer system or other conventional instruments, or it can be made into explosion-proof or fireproof measuring instruments as required by users.

Pressure transmitter

Pressure transmitter, also known as stubble transmitter, is mainly composed of load cell sensor, module circuit, display meter head, case and process connector. It can be received gas, liquid and other pressure signals into the standard current and voltage signal, to supply indicator alarm, recorder, regulator and other secondary instruments for measurement, indication and process adjustment.

Principle of measurement of the pressure transmitter, flow pressure, and reference, respectively applied to the ends of the integrated silicon pressure sensor, the differential pressure make the silicon wafer deformation (displacement is very small, only microns), so that the silicon wafers made of semiconductor technology, full-motion hui stearns bridge in external driven by current source output is proportional to the pressure of the mV level of voltage signal, and sent to a high magnification and can cancel each other out temperature drift of a differential amplifier. After amplification, the signal is converted into the corresponding current signal through voltage and current conversion. After nonlinear correction, the standard current and voltage signal with a linear correspondence with the input pressure is finally generated.

Pressure transmitter can be divided into general pressure transmitter (0.001MPa ~ 20MP3) and differential pressure transmitter (0 ~ 30kPa) according to the pressure measurement range.

Iii. Liquid level transmitter

1. Floating ball type liquid level transmitter

The floating ball type liquid level transmitter is composed of magnetic floating ball, measuring pipe, signal unit, electronic unit, junction box and mounting parts.

Generally, the specific gravity of magnetic floating ball is less than 0.5, which can float above the liquid level and move up and down along the measuring pipe. The catheter is equipped with a measuring element, which can convert the measured WeChat ID into a resistance signal proportional to the changing resistance signal under external magnetic action, and convert the electronic unit into 4-20ma or other standard signal output. The transmitter is a module circuit with the advantages of acid resistance, moisture resistance, shock resistance, corrosion resistance, etc., the circuit contains constant current feedback circuit and internal protection circuit, which can make the maximum output current does not exceed 28mA, so as to protect the power supply reliability and secondary instrument is not damaged.

2. Floating simple liquid level transmitter

The buoy type liquid level transmitter changes the magnetic buoyancy ball into the buoy, it is according to Archimedes buoyancy principle design. Floating-type liquid level transmitter USES tiny metal membrane strain sensing technology to measure liquid level, boundary level or density. It can carry on the regular setting operation through the field key when working.

3. Static pressure or liquid level transmitter

The transmitter works on the principle of hydrostatic pressure measurement. It generally USES silicon pressure sensor to convert the pressure measured into electrical signals, after amplification circuit and compensation circuit, and finally output in 4~20mA or 0~10mA current mode.

Capacitance level transmitter

Capacitive level transmitter is suitable for industrial enterprises to measure and control the production process in the production process, mainly used as conductive and non-dielectric liquid level or granular solid level of long-distance continuous measurement and indication.

Capacitive liquid level transmitter is composed of capacitive sensor and electronic module circuit. It takes 2-wire system 4-20ma constant current output as the base type. After conversion, it can be output in three-wire or four-wire mode. Capacitance sensors consist of insulated electrodes and cylindrical metal containers containing measuring media. When the material level rises, the dielectric constant of non-conductive material is significantly lower than that of air, so the capacitance changes with the change of material height. The module electric furnace of transmitter is composed of reference source, pulse width modulation, conversion, constant discharge, feedback and current limiting units. The advantage of using pulse width modulation principle for measurement is low frequency, good stability, good linearity, no obvious temperature drift and so on.

Five, ultrasonic transmitter

Ultrasonic transmitter is divided into general ultrasonic transmitter (no head) and integrated ultrasonic transmitter two categories, integrated ultrasonic transmitter is more commonly used.

The integrated ultrasonic transducer is composed of two parts: the meter head (such as LCD display) and the probe. The transmitter that directly outputs 4 ~ 20mA signals is to assemble the miniaturized sensor (probe) and electronic circuit together, so as to make it smaller in size, lighter in weight and cheaper in price. Ultrasonic transmitter can be used for liquid level. The measurement of object level and flow measurement of open channel and open channel can be used to measure distance.

Antimony electrode acidity transmitter

Antimony electrode acidity transmitter is an industrial on-line analytical instrument integrating PH detection, automatic cleaning and electrical signal conversion. It is a PH measurement system composed of antimony electrode and reference electrode. In the acid solution under test, the potential difference between the metallic antimony surface and antimony trioxide is formed because antimony oxide layer is formed on the surface of antimony electrode. The magnitude of the potential difference depends on the concentration of antimony oxide, which corresponds to the moderate concentration of hydrogen ions in the acid solution under test. If antimony, antimony trioxide, and the moderation of aqueous solution are considered as 1, the electrode potential can be calculated by nernst formula.

The solid module circuit of antimony electrode acidity transmitter consists of two parts. For the safety of the field function, the power supply part USES 24V ac to supply power for the secondary instrument. In addition to providing the driving power for the cleaning motor, the power supply should be converted into the corresponding dc voltage through the current conversion unit for the use of the transformer circuit. The second part is to measure the transmitter circuit, which amplifies the reference signal from the sensor and PH PH signal and sends it to the slope adjustment and positioning adjustment circuit, so as to reduce the internal resistance of the signal and adjust it. After the amplification of PH signal and temperature compensated signal are superposed, the differential conversion circuit will be used to output the 4-20ma constant current signal corresponding to PH value to the secondary instrument to complete the display and control of PH value.

Seven, acid, alkali, salt concentration transmitter

Acid, alkali and salt concentration transmitters determine the concentration by measuring the conductivity of the solution. It can continuously detect the concentration of acid, alkali and salt in aqueous solution in the industrial process online. This transmitter is mainly used in boiler feed water treatment, chemical solution preparation and environmental protection and other industrial production processes.

The working principle of acid, alkali and salt concentration transmitter is: within a certain range, the concentration of acid and alkali solution is proportional to its conductivity. Therefore, as long as the conductivity of the solution is measured, the concentration of acid and base can be determined. If electrode polarization and distributed capacitance are ignored, the measured solution can be equivalent to a pure resistance when flowing into a dedicated conductivity cell. When there is constant voltage alternating current flowing, the output current has a linear relationship with the conductivity, and the conductivity is proportional to the concentration of acid and alkali in the solution. Therefore, as long as the current of the solution is measured, the concentration of acid, base and salt can be calculated.

Acid, alkali, salt concentration transmitter is mainly composed of conductivity pool, electronic module, display head and shell. Electronic module circuit is composed of excitation power supply, conductance pool, conductance amplifier, phase sensitive rectifier, demodulator, temperature compensation, overload protection and current conversion units.

Conductivity transmitter

It is a process instrument that indirectly measures ion concentration by measuring the conductivity value of solution (integrated transmitter), which can continuously measure the conductivity of aqueous solution in industrial process online.

Since electrolyte solutions are as good conductors of electricity as metallic conductors, there must be resistance when current flows through electrolyte solutions, and this is in accordance with ohm's law. But the resistance temperature characteristic of liquid is opposite to that of metal conductor and has negative temperature characteristic. To distinguish an electrolyte solution from a metallic conductor, the conductivity of the electrolyte solution is expressed as the conductivity (reciprocal of the resistance) or the conductivity (reciprocal of the resistivity). When two insulated electrodes form a conductance cell, a current loop is formed if the solution to be tested is placed between them and a constant voltage alternating current is applied. If the voltage size and electrode size are fixed, there is a functional relationship between loop current and conductivity. In this way, the conductivity of the solution under test can be measured by measuring the current flowing through the solution under test.

The structure and circuit of the conductivity transmitter are the same as that of the acid, alkali and salt concentration transmitter.

Nine, intelligent transmitter

Intelligent transmitter is composed of sensors and microprocessors (microcomputers) phase structure. It makes full use of the computing and storage capabilities of the microprocessor to process the sensor data, including the adjustment of the measurement signal (such as filtering, amplification, A/D conversion, etc.), data display, automatic correction and automatic compensation.

Microprocessor is the core of intelligent transmitter. It can not only calculate, store and process the measurement data, but also adjust the sensor through the feedback loop, so as to achieve the optimal data collection. Because the microprocessor has a variety of software and hardware functions, so it can complete the traditional transmitter difficult to complete the task. Therefore, the intelligent transmitter reduces the manufacturing difficulty of the sensor and improves the performance of the sensor in a large range. In addition, intelligent transmitter also has the following characteristics: with automatic compensation ability, the sensor can be automatically compensated by software for non-linear, temperature drift, time drift, and so on.

The sensor can be self-diagnosed and self-tested after power on to check whether all parts of the sensor are normal and make a judgment. Data processing is convenient and accurate. Data can be automatically processed according to internal procedures, such as statistical processing and removing abnormal values. With two-way communication function. The microprocessor can not only receive and process sensor data, but also feedback information to the sensor, so as to adjust and control the measurement process.

It can store and remember information, and can store sensor characteristic data, configuration information and compensation characteristics. With the digital quantity interface output function, the output digital signal can be easily connected with the computer or field bus.

Ten, thermal resistance partition transmitter

RTT2 thermal resistance isolation transmitter is mainly used in the control system to convert a group of thermal resistance signals in the field into two groups of 4-20ma standard current signals, and isolate the transmission to the control room of DCS and other system control equipment. It is widely used in distributed control system (DCS), monitoring and data acquisition system (SCADA), environmental monitoring system (EMCS), and so on. Input, output, power supply are isolated from each other.

Previous post:

Next post:

TypeInfo: Product information

Keywords for the information:

Tinko Instrument (Suzhou) Co., Ltd.
天天贵阳麻将官方网站 甘肃快三精准计划 十一运夺金助手彩乐乐 12121期体彩排列5 股票涨跌历史 内蒙古十一选五开奖结果查询一定牛 江苏十一选五走势图定牛 广东快乐十分出号分析 喜乐彩票合法吗 官方 山东十一运夺金推荐 万科a股票