Applications of Wheatstone Bridge The Wheatstone bridge circuit can be used to precisely measure resistance. However, the bridge is most commonly used in conjunction with transducers to measure physical quantities such as strain, temperature, and pressure. Transducers are devices that sense a change in a physical parameter and convert that change into an electrical quantity […]
Function of Encoder An encoder is a combinational logic circuit that accepts one or more inputs and generates a multibit binary output. Encoding is the process of converting any keyboard character or number as input to a coded output such as a binary or BCD form. Figure 1 shows a decimal-to-binary encoder. Its function is
In many situations, the raw output of the sensor may not be in a form suitable to be interfaced to a measurement device or an A/D convertor, and some form of signal conditioning is needed to be applied to the sensor output. These signal conditioning operations include filtering, amplification, or using a bridge circuit. In
There are a number of parameters that characterize sensors’ performance. The time-independent characteristics are called the static characteristics, while the time-dependent characteristics are called the dynamic characteristics. The static characteristics characterize the sensor output after it has settled due to changes in the physical quantity being measured. The dynamic characteristics describe the sensor characteristics from
Distinctive Thermocouple Noise Problems Thermocouple emfs are small. Fine temperature resolution requires substantial amplification. For quasi-static thermometry, modern noise suppression techniques available to designers of data loggers overcome ordinary coupled electrical noise to routinely achieve as small as 0.1 °C temperature resolution and long-term stability (much smaller than required by thermocouple tolerance). Thermocouple measurement of
Thermocouple Thermometry Practice Temperature Ranges Moderate and High Temperatures: Temperature and duration of exposure are unavoidable environmental variables in thermometry. Other environments can sometimes be controlled. Standard thermocouple tables extend only to the greatest temperature of recommended use for benign protected environments, short durations, and for wire materials of 3 mm or greater diameter. Reduced
Calibration of Thermocouples Thermocouple calibration is intended to improve accuracy. Conventional calibration might not. Calibration of a sample from a uniform set of as-delivered thermocouples to confirm conformity to standard tolerance is appropriate. However, despite individual calibration, the approximated standard scaling relation, rather than the actual calibration, usually is used in thermometry regardless of calibration
Active Tests of Thermocouple Manufacturers routinely apply quality control to their thermocouple products, yet users are responsible locally to assure that no occasional defect, error, or change has occurred in manufacture or installation. Several simple and routine test procedures are available to the user. Symptom and Occurrence of Inhomogeneity Thermoelectric inhomogeneity, though now widely misunderstood,
Thermocouple Junction Styles Junction designs vary widely for specialized application. Most junctions are very localized. Some, to average surface temperature along a line, have widely extended a junction between foil thermoelements. Measuring and reference junctions are conspicuous. However, the many incidental junctions are inconspicuous and may not be recognized yet, uncontrolled; their temperatures can significantly
Thermocouple Hardware Material Sources Thermoelectric alloys and thermoelements are manufactured by a very few specialized sources. These manufacture bare thermoelement bar stock, wire, and foil, and selectively pair thermoelements for thermocouples. Fewer sources fabricate the MIMS thermocouple materials that are incorporated by others into finished products. These producers of basic forms and very many other