Radiation pyrometer

Subject: instrument and process control

1. Government Engineering College, Bharuch. Sub:-Instrumentation & Process Control Topic:-Radiation Pyrometer Sem :5 th Prepared by

2. Radiation Pyrometer Pyrometer:- A pyrometer is a device that is used for the temperature measurement o f an object. The device actually tracks and measures the amount of heat that is radiated from an object. The thermal heat radiates from the object to the optical system present inside the pyrometer. The optical system makes the thermal radiation into a better focus and passes it to the detector. In an optical pyrometer, a brightness comparison is made to measure the temperature.

3. The device compares the brightness produced by the radiation of the object whose temperature is to be measured, For an object, its light intensity always depends on the temperature of the object. After adjusting the temperature, the current passing through it is measured using a multimeter, as its value will be proportional to the temperature of the source when calibrated. Pyrometry is a technique for measuring temperature without physical contact. It depends upon the relationship between the temperature of hot body and electronic magnetic radiation emitted by the body.

4. Types of Pyrometer The following are some of the most commonly and widely used pyrometer: Optical pyrometer Radiation pyrometer Digital pyrometer Infrared pyrometer

5. Radiation pyrometer   Working construction:- The radiation pyrometer has an optical system, including a lens, a mirror and an adjustable eye piece. The heat energy emitted from the hot body is passed on to the optical lens, which collects it and is focused on to the detector with the help of the mirror and eye piece arrangement.

6. The detector may either be a thermistor or photomultiplier tubes. Though the latter is known for faster detection of fast moving objects, the former may be used for small scale applications. Thus, the heat energy is converted to its corresponding electrical signal by the detector and is sent to the output temperature display device.

7. Advantages:- Easy to operate High output . Moderate cost . It is simple in design and construction. Ability to measure high temp. It has Fast speed o response. It has no physical contact with target of measurement . Disadvantages:- Emissivity errors are introduced It is relatively expensive. The radiation pyrometer is complex in nature. External radiation may affect the measurement. Emissivity of target material affecting measurement. It has non linear scale. Errors due to the absorption of radiation by carbon dioxide, water or other apparently transparent gases.

8. Application:- They are used for temperatures above the practical operating range of thermocouples. They can be used in the environments which contaminate or limit the life of thermocouple. Used for moving targets. They are used for measurement of average temperature of large surface areas. They are used for the targets which would be damaged by contact with primary elements like thermocouples and resistance thermometers.

9. Limitations of Radiation Pyrometer Availability of optical materials limit on the wavelengths that can be measured. The surface of the hot object should be clean It should not be oxidized. Scale formation does not allow to measure radiation accurately. Emissivity correction is required. Chane in emissivity with temp need to consideration.

10. Thank you…