SenTec has been focusing on the development and manufacture of type s thermocouple armored platinum-rhodium thermocouple transmitter for many years. The company mainly produces platinum-rhodium S-type thermocouples, wear-resistant high-temperature resistant thermocouples, and S-type platinum-rhodium high temperature probes, which are widely used in metallurgy, petroleum, chemical industry, cement, electric power, machinery and laboratories and other fields.
Introduction of type s thermocouple transmitter
A thermocouple transmitter is an instrument that converts a temperature variable into a transmittable, standardized output signal. Mainly used for the measurement and control of industrial process temperature parameters.
A transmitter with a sensor usually consists of two parts: a sensor and a signal converter. Sensors are mainly thermocouples or thermal resistances; signal converters are mainly composed of measurement units, signal processing and conversion units (since industrial thermal resistances and thermocouple scales are standardized, signal converters are also called as independent products. Transmitter), some transmitters add display unit, and some also have fieldbus function. Principle of thermocouple temperature transmitter.
If the transmitter is composed of two sensors used to measure the temperature difference, there is a given continuous function relationship between the output signal and the temperature difference. It is called a temperature thermocouple transmitter.
There is a given continuous function relationship (usually a linear function) between the output signal of the transmitter and the temperature variable. The output signal of the early production transmitter has a linear function relationship with the resistance value (or voltage value) of the temperature sensor.
The standardized output signals are mainly DC signals of 0mA~10mA and 4mA~20mA (or 1V~5V). Other standardized output signals with special provisions are not excluded.
Thermocouple transmitter can be divided into two-wire and four-wire system according to the power supply wiring mode. Transmitter has electric unit combination instrument series (DDZ-Ⅱ type, DDZ-Ⅲ type and DDZ-S type) and miniaturized modular type, multi-functional intelligent type. The former do not have sensors, and the latter two types of transmitters can be easily combined with thermocouples or thermal resistances to form transmitters with sensors.
Material requirements for type s thermocouple protection tube
Thermocouple is a commonly used temperature measuring instrument, which has important applications in many fields. Thermocouples need protection tubes in the production process, so what are the material requirements for thermocouple protection tubes?
The material used to make the thermocouple protection tube should generally meet the following requirements:
1. It should have sufficient mechanical strength, bending resistance, compression resistance, and not easy to damage;
2. Good thermal conductivity and small heat capacity, in order to reduce the inertia of thermocouple temperature measurement, so that the temperature difference inside and outside the protection tube is not too large;
3. It has good air tightness to prevent the measured medium from penetrating into the tube to corrode or damage the hot electrode, resulting in errors or economic losses;
4. The physical and chemical properties are stable, and in the long-term use process, especially in the case of high temperature, it will not react with the measured medium to produce gases that are harmful to the thermode;
5. When measuring corrosive media such as acid, alkali, salt, etc., the material selected for the protection tube should be able to resist the corrosion of harmful media; select the corresponding material for different test environments;
Working principle and model selection of platinum-rhodium type s thermocouple
The long-term maximum operating temperature of platinum-rhodium type s thermocouples is 1300 °C, and the short-term maximum operating temperature is 1600 °C.
The platinum-rhodium type s thermocouple has the advantages of the highest accuracy, the best stability, wide temperature measurement range and long service life among the thermocouple series. Good performance, suitable for oxidizing and inert atmospheres, due to the excellent comprehensive performance of platinum-rhodium type s thermocouples, the type s thermocouples that meet the international temperature scale have long been used as an interpolation instrument for international temperature scales, although regulations will not be used in the future.
It is used as an internal inspection instrument for the international temperature scale, but the International Temperature Advisory Committee (CCT) believes that the platinum-rhodium type s thermocouple can still be used to approximate the international temperature scale. , The sensitivity is low, the mechanical strength is reduced at high temperature, it is very sensitive to pollution, and the precious metal materials are expensive, so the one-time investment is large.
The working principle of the platinum-rhodium s-type thermocouple is that when the platinum-rhodium S-type thermocouple is composed of two conductors with different components connected at both ends into a loop, when the temperature of the two junctions is different, a thermal current will be generated in the loop.
If there is a temperature difference between the working end and the reference end of the platinum-rhodium S-type thermocouple, the display instrument will indicate the temperature value corresponding to the thermoelectric potential generated by the platinum-rhodium S-type thermocouple. Selection of platinum-rhodium type s thermocouple: it is recommended to use single platinum-rhodium thermocouple (platinum-rhodium 10-platinum) when the measured temperature is normally 1000~1300℃, and double platinum-rhodium thermocouple is recommended when the measured temperature is normally 1200~1600℃ Coupled (platinum rhodium 30-platinum rhodium 6), so that the service life of platinum rhodium S-type thermocouple can be guaranteed within the temperature range used.
The difference between type s armored platinum-rhodium thermocouple and fabricated platinum-rhodium thermocouple
S-type armored platinum-rhodium thermocouple and S-type fabricated platinum-rhodium thermocouple are used to measure temperature in use, but S-type armored platinum-rhodium thermocouple and S-type fabricated platinum-rhodium thermocouple are used in actual operation. There are also differences in the process.
The S-type armored platinum-rhodium thermocouple can be bent arbitrarily during use and the measurement temperature range is comparable to that of the S-type assembled platinum-rhodium thermocouple. The overall performance of the S-type armored platinum-rhodium thermocouple is better than that of ordinary thermocouples. And the performance is stable. Armoring is more suitable for some special occasions, such as temperature measurement in some occasions, which needs to be bent and the pipeline is narrow. Ordinary thermocouples cannot meet this requirement.
The type s assembled platinum-rhodium thermocouple cannot be bent during use. It is usually made of 16 mm or other diameter corundum ceramics as a protective cover, with corundum core as insulation protection, and then a junction box is installed. It is suitable for large-area temperature measurement occasions. It has the advantages of shock resistance, pressure resistance, burning resistance, high temperature resistance, long service life, and diversified installation methods. If it is damaged during use, it can be replaced without stopping, which greatly reduces production costs.
S-type armored platinum-rhodium thermocouple and S-type assembled platinum-rhodium thermocouple have their own advantages. Users can make reasonable choices according to their needs, which is convenient to reduce costs and improve production efficiency.
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