Friday, February 5, 2010

Temperature, Radiation Measurement Devices & Methods

The first question is what the definition of temperature is. Temperature is a feeling of warmth or coldness of an item which can recognize by touching that item. In fact, “temperature is a measure of the average kinetic energy of the particles in a sample of matter, expressed in units of degrees on a standard scale.” Temperature units are in Fahrenheit or centigrade degrees. Since temperature is a standard measurement, the amount of particles in an object does not change the temperature range and also temperature does not depend on the size of the object. For instance, the temperature in a glass of boiling water is exactly same as the temperature of the huge tank of boiling water and it doesn’t matter that big tank carry more water molecules inside.

The particles and molecules in the objects never travel at the similar speed. Indeed there is a variety of energy in the middle of the molecules which cause the movement. Like in glass of liquid like water molecules are moving in the accidental way with different range of speed and the pace of the molecules depend on the temperature on the liquid. It means with higher temperature molecules move faster and with lower they move slower.

Temperature needs to get measure in different circumstances and
there are plenty of equipments and sensors outside for measuring it. First common and practical device to measure temperature is thermometer. Thermometer work really simple and has two main elements, the temperature sensor and some numbers to converting the material change into a value.

Most frequently used temperature sensor is thermocouple. The thermocouple made from two different metals which are attached jointly at the end of one side. They touch each other and the contact point produces a small exclusive voltage as a function of temperature. This voltage is measured and read by a thermocouple thermometer. Thermocouples are accessible in diverse “metals combinations or calibrations. The four important calibrations of the thermocouples are J, K, T and E. Each calibration has a special temperature variety and environment.” Although the thermocouples are sort of
temperature sensor which generally use for measurement and control they be capable to use to convert heat into electric forces. In the direction of choosing the right thermocouples for our project we need to consider different aspect of it. Since thermocouples measure in large temperature ranges and can be quite rough they are usually getting used in manufacturing. So we need to consider the temperature range, think about the chemical resistance of the thermocouple or covered material, consider abrasion and vibration resistance and at the end check our installation supplies.

One of the disadvantages of thermocouple is life time of the machine. Since in thermocouples, thermo elements are usually worked in the high temperatures the lifetime of the system will decrease. One of the electronic devices which can convert thermal energy to electrical energy is thermopile. Thermopile is a collected of thermocouples most regularly in series connection but in some special cases in parallel.

1 comment:

Mike Carter said...

Thanks so much for sharing this. I am going to be using temperature measurement devices for the first time at my upcoming lab. We haven't done anything like it yet so I'm really looking forward to doing it.