Unit 1 Выучите слова и выражения:

measurement - параметр

thermocouple - термопара

resistance temperature device - элемент термосопротивления

infared thermometry - инфракрасная термометрия

thermistor - термистор

integrated circuit sensor - интегральная схема датчиков

radiation pyrometer - радиационный пирометр

circuitry - схема

coil - спираль

probe assembly - блок исследования

temperature range - интервал температур

Text 1A. Temperature Sensors for Use in Food Processing

One of important measurements in food processing is measurement of the amount of energy; that a body is projecting. Any food product that is not sold as fresh must be heated to a specifired temperature for a specifired time period to insure that any microorganisms that were present are destroyed. There are different types of temperature sensors. These include thermocouples, resistance temperature devices, infared thermometry, thermistors and integrated circuit sensors.

The need for a more practical temperature scale has led international standards organization to create the International Temperature Scale. It is based upon several basic temperature points. These points include melting, freezing points and triple points of very pure materials. All electronic temperature 'sensors are calibrated against the International Temperature Scale.

Resistance temperature devices work on the principle that the electrical resistance of conductive material increase proportionally to the temperature of the material.

Resistance temperature devices consist of a. coil of wire (usually platinum or nickel) wound, around a small ceramic bobbin. Each end of the coil is connected to low resistance copper wiring which is connected to a resistance copper wiring which is connected to an resistance temperature device input module.

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ctronic circuitry in

The electronic circuitry in the module converts the resistance across the sensing ;oil to a temperature based on data from the national standards.

The most basic temperature sensor is the thermocouple. A thermocouple is junction of two dissimilar metals. This junction creates a very low electro- magnetic field which increases in a linearly manner with respect to absolute temperature. This electro-magnetic field induces a very low current in the circuit. Thomas Seebeck discovered this effect in 182.1 and the voltage induced is known as the seebeck voltage. This voltage is read by a specialized thermocouple input module and converted to a standard temperature. Thermocouples are the most robust temperature sensor and it can be packaged in .i small profile sensor, which lessens the chance of sinking heat into the щоре d '"' issembly. Thermocouples also have a short reaction time due to their low mass. They are the most a small profile sensor, which lessens the chance of sinking heat into the probe assembly. Thermocouples also have a short reaction time due to their low mass. They are the most available temperature sensors.

Resistance temperature devices are generally more stable, accurate and sensitive than thermocouples, but cover a smaller temperature range and react to changes in temperature slower than thermocouples.

Infared thermometry is the measurement of temperature by analyzing the energy of a body is emitting in the infared spectrum. These measurements are taken with a radiation pyrometer. The pyrometer focuses on an object and measures the amount of radiation that the object is emitting at a specific frequency in the infared spectrum, typically at a wavelength of six microns.

Radiation pyrometers are expensive and very difficult to set up and calibrate, because they work on light emission.

Infared thermometry does offer several unique features. The object that is being measured is never touched.

When selecting an electronic temperature measurement device there are several items that should be taken into account. These include temperature range, accuracy, reaction time and cost.