Resistive Thermal Detectors RTDs

For most points requiring temperature monitoring, either thermocouples or resistive thermal detectors (RTD s) can be used. Each type of temperature transducer has its own advantages and disadvantages, and both should be considered when temperature is to be measured. Since there is considerable confusion in this area, a short discussion of the two types of transducers is necessaiy. 

Resistive Thermal Detectors (RTDs) RTDs determine temperature by measuring the change in resistance of an element due to temperature. Platinum is generally utilized in RTDs because it remains mechanically and electrically stable, resists contaminations, and can be highly refined. The useful range of platinum RTDs is... 

Figure 2.1 Thermal behavior of a thermistor [1] and a platinum resistance temperature detector (RTD) [2],...

Contact temperature sensors represent a class of temperature probes that are used to determine the temperature of a medium through the thermal equilibrium attained between the sensor and the medium when in contact. The change in the medium temperature is inferred from a corresponding variation in the sensor resistance or output voltage, which can be used to obtain the temperature difference via an a priori calibration of the sensor output with temperature. The commonly implemented contact temperature sensors include thermocouples, resistance temperature detectors (RTDs), and thermistors. 

Until recently, temperature measurements in microfluidic systems were limited to measures of bulk fluid temperature at the inlet and outlet of microfluidic sections or simply measurement of the substrate temperature. With regard to local temperature measurements, thermocouple probes provide highly accurate measures of fluid and/or substrate temperature with excellent temporal response. However, thermocouples can often be physically intrusive and generally suffer from poor spatial resolution since most probes have a characteristic size of several micrOTs or more. Alternatively, microfluidic devices can be fabricated with integrated microscale resistance temperature detectors (RTDs s) embedded in the substrate with spatial extents on the order of a few microns [13]. Micro-RTDs overcome the intrusiveness issues of thermocouples however, their fabrication can be quite complex and RTDs still suffer from poor spatial resolution which limits their ability to resolve local thermal... 

Temperature Heat and cold Resistance temperature detectors (RTDs), thermistors Heat Thermal devices Detection of body as well as environmental temperature... 

The value of P is on the order of 4000, so at room temperature (298 K), Or = -0.045 for thermistor and 0.0035 for 100-f2 platinum RTD. Compared with RTDs, NTC-type thermistors are advantageous in that the detector dimension can be made small, resistance value is higher (less affected by the resistances of the connecting leads), and it has higher temperature sensitivity and low thermal inertia of the sensor. Disadvantages of thermistors to RTDs include nonlinear characteristics and low measuring temperature range. 

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