Temperature

Temperature

Temperature

Temperature measurement in today’s industrial environment encompasses a wide variety of needs and applications.

To meet this wide array of needs the process controls industry has developed a large number of sensors and devices to handle this demand.

Many methods have been developed for measuring temperature.

Temperature measurement can be classified into a few general categories:

  • Thermometers
  • Probes
  • Non-contact

Thermometers are the oldest of the group.

Thermometers

A thermometer is an instrument that measures temperature. It can measure the temperature of a solid such as food, a liquid such as water, or a gas such as air.

The three most common units of measurement for temperature are Celsius, Fahrenheit, and kelvin.

Bimetal Thermometer

Bimetallic thermometers are made up of bimetallic strips formed by joining two different metals having different thermal expansion coefficients.

Basically, bimetallic strip is a mechanical element which can sense temperature and transform it into a mechanical displacement.

This mechanical action from the bimetallic strip can be used to activate a switching mechanism for getting electronic output. Also it can be attached to the pointer of a measuring instrument or a position indicator.

Various techniques such as riveting, bolting, fastening can be used to bond two layers of diverse metals in a bimetallic strip.

How ever the most commonly used method is welding. Since two metals are employed to construct a bimetallic strip, hence the name.

Probes

Following the development of the thermometer, the next step in the evolution of temperature measurement was the development of the temperature probe. In 1826 an inventor named Becquerel used the first platinum-vs-palladium thermocouple.

Prior to this time all temperature measurement was done with liquid or gas filled thermometers. The invention of the thermocouple ushered in a whole new wave of development, culminating in what we know today as practical thermometry.

Read More  Head mount temperature transmitter KROHNE

This resistance element was the first in a series of devices that are not classified as probes or transducers. These fall into three general categories:

  • Resistance elements
  • Thermopiles
  • Semiconductor

Resistance elements

Resistance elements were the first probes that came into being. Early inventors understood the relationship between temperature and the resistance of different elements. This gave rise to a series of elements called thermistors.

Thermistors

The thermistor is a device that changes its electrical resistance with temperature. In particular materials with predictable values of change are most desirable. The original thermistors were made of loops of resistance wire, but the typical thermistor in use today is a sintered semiconductor material that is capable of large changes in resistance for a small change in temperature.

RTD

The Resistance Temperature Detector (RTD) technically includes thermistor devices, however the term ‘RTD’ has come to stand for the specialized pure metal detector rather than the more generic semiconductor resistance element. These pure metal devices are highly accurate and stable over long periods of time.

Here many kinds of temperature products from the best brands at the whole of the world.
All the temperature products have made from the best materials that fit with your process and varios of media.
So Saba Dejlah can help you to choose the best thermometer.

You can choose from WIKA,Ashcroft ,….and any brand that you want.

 

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