How,Choose,The,Correct,Tempera technology How to Choose The Correct Temperature Sensor?

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These showregular changes of the physical nature of the main body. Temperature sensor isa core part of the temperature measuring instruments, which is a wide variety.By measuring method it can be divided into two major categories: contact andnon-contact. According to characteristics of the sensor materials and electroniccomponents, sensor are divided into two types of RTD andthermocouple. If you want to make reliable temperature measurements, you needfor your application to select the correct temperature sensor. Thermocouple,thermistor, platinum resistance (RTD) and the temperature is the most commonlyused IC temperature sensor in the testThermocoupleThermocouple is the most commonly used sensor in the temperature measurement.Its main advantage is a wide temperature range and adapt to the atmosphericenvironment, and strong, low price, without power, especially the cheapest.Thermocouple connected at one end by the two different metal lines form, whenheated at one end of the thermocouple, thermocouple circuit potentialdifference there. Potential difference measurements can be used to calculatethe temperature.However, the nonlinear relationship between voltage and temperature is shown asbelow. And because of this, the need for the reference temperature (Tref) forthe second measurement, and the use of test equipment software and / orhardware within the instrument handle voltage - temperature changes, to finallyget the thermocouple temperature (Tx). Agilent34970A and 34980A dataacquisition system equipped with an internal measure of computing power.In short, the thermocouple is the simplest and most common temperaturesensors, but the thermocouple is not suitable for precision applications.ThermistorThermistor is a semiconductor material; most of them arenegative temperature coefficient, i.e. resistance decreases with increasingtemperature. Temperature changes will cause a large resistance to change, so itis the most sensitive temperature sensor. But poor linearity of the thermistor,and a great relationship with the production process. Manufacturers to notstandardized thermistor curves.Thermistor is very small; the response to temperature change is also fast. Butneed to use the thermistor current source, the small size also makes itextremely sensitive to the self-heating errors.Thermal resistance measurement in the two lines is the absolute temperature andbetter accuracy, but it is expensive even than the heat can be measured is lessthan the thermocouple temperature range. A common thermistor resistance at 25 to 5k©, per 1  temperature change caused by changes in the resistance 200©.Note 10© lead resistance caused only a negligible error of 0.05 . It is idealfor fast and sensitive measurement of current temperature control applications.Small size for applications requiring a space is beneficial, but must be takento avoid self-heating errors.Measurement TechniquesThermistor is small is an advantage, it can quickly stabilize and will notcause heat load. But also it not enough strong, high current will causeself-heating. As the thermistor is a resistive device, any current source willbe in on it because of power caused by heat. Power equal to the square of thecurrent and the resistance of the product. Therefore, to use a small currentsource. If the thermistor is exposed to heat, will result in permanent damage.Platinum Resistance Temperature SensorSimilar to the thermistor, platinum resistance temperature detector (RTD) ismade of heat-sensitive platinum resistance. When the voltage is calculated bymeasuring the RTD temperature, digital multimeter measuring current source witha known source of the current generated by voltage. The voltage of two lead(Vlead) plus the voltage drop on the voltage on the RTD (Vtemp). For example,commonly used RTD resistance of 100©, per 1  produced only 0.385© resistancechanges. 10© per lead if there is resistance, it will result in 26  formeasurement error, which is unacceptable. It should be 4-wire Ohm RTDmeasurement.RTD is the most accurate and stable temperature sensor, and its linearity overthe thermocouple and thermistor. But also the slowest and most expensive RTDtemperature sensor. Therefore, the most suitable for precision RTD strictrequirements, speed and price is not a key application.Temperature ICTemperature integrated circuit (IC) is a digital temperature sensor, it has avery linear voltage / current - temperature relationship. Some even haverepresentatives of the temperature sensor IC, and the microprocessor can beread directly form the digital output.Two temperature Ics have the following temperature relationship:1. Voltage IC: 10 mV / K.2. Current IC: 1¼A / K.The output temperature IC output is very linear voltage / . Voltage isactually produced / Kelvin, so when the room temperature 1  output of about3V. Temperature IC requires external power supply. Temperature of IC is usuallyembedded in the circuit and not used for detection.Temperature IC drawback is the limited range of temperature, there arealso the same self-heating is not strong and needs external power supplyproblems. In short, the IC provides temperature that is proportional to thetemperature readings readable way. It is cheap, but also by the configurationand the speed limit.Measurement Techniques:• Temperature IC bulky, so it changes slowly, and may result in heat load.• Take the temperature IC to the close room temperature occasion; this is itsmost popular applications. Although the range is limited, but can also measurethe temperature of 150 .We have discussed the various types of commonly used temperature sensors theadvantages and disadvantages. If you understand the necessary balance for yourapplication carefully select the right sensor, you can avoid commonshortcomings and reliable temperature measurement Article Sourcehttp://www.hqew.net/events/news-article/269.html