**1. Introduction**

A temperature sensor is an electronic device that measures the temperature of its environment and converts the input data into electronic data to record, monitor or communicate temperature changes. A temperature sensor is an electronic device that monitors the temperature of its surroundings and turns the input data into electronic data. Temperature sensors come in a wide variety of forms [1].

Temperature sensors are electrical/electronic physical sensing device which transforms an input signal from a specific environment into an equivalent output signal [2].

According to the amount of general literature on the topic, thermocouples are the most often employed type of temperature measuring in industry. Its widespread acceptance, reasonable accuracy over a wide measurement range, and relatively inexpensive sensors all contribute to its appeal. Narrower measuring ranges can handle

accuracy closer to 0.1 degrees Celsius, whereas accuracy over wide ranges is comfortably between 0.5 and 2 degrees Celsius [3].

As long as the Seebeck coefficients of material A and material B for the two materials are known, these thermoelectric devices use the Seebeck effect in dissimilar metal wires linked at the thermoelectric junction representing T1 to determine a temperature gradient down the wire [4]. The temperature can be gauged at the terminus connections T0 by measuring the net electromotive force between T0 and T1 within the wires, which is voltage of the order of microvolts. Cold junctions are frequently utilised in the form of a fixed physical temperature or electronically mimicked via cold junction compensation because a temperature gradient must be constructed to produce a net voltage output signal (CJC).

Due to the non-linear temperature-resistance connection of thermistors, which are composed of semiconductor materials, calibration is even more crucial [5]. Although routine calibration is required to prevent the impacts of sensor drift, the use of semiconductor materials allows them to deliver a far better level of sensitivity [6] than other sensor types.

According to Schweiger's 2007 argument, if the right sensors are chosen and calibrated properly, a quick multichannel precision thermometer might compete with Precision Thermometers using thermistors [7]. Deviations of less than 30 mK were seen in tests conducted in the temperature range of 50 to 10 C. Improvements have been made in spatial resolution of surface temperature measurement compared to standard soldered type K thermocouple using an electrochemically etched microtip [8]. Thin film thermocouples can also be deposited onto a surface and have been used to measure heat generated in the friction between sliding surfaces [9]. Non-linearity

**Figure 1.** *Temperature-Sensing illustration [12–14].*

**Figure 2.** *Temperature sensor [15].*

of sensors can be an issue, although one study showed it to be possible to correct for this using a neural network approach in type K thermocouples [10].

Industrial thermocouple measurements can be further enhanced by improving high-temperature alloys and more intelligent electronics [11].

**Figure 1** shows an illustration of temperature-sensing using human hands as a sensor and its digital equivalent, while **Figure 2** shows a temperature sensor formed by joining two different materials. There are many different types, sizes and shapes of temperature sensors. In general, temperature sensors can be categorised into two groups: contact sensors and non-contact sensors [15].
