Loop powered digital-to-analog converter (DAC) the AD5700, The circuit also includes the AD5421, a 16-bit, 4 mA to 20 mA, The circuit uses the AD7124-4, an ultralow power, precisionĢ4-bit, Σ-Δ analog-to-digital converter (ADC), which includesĪll the features needed for temperature and pressure systems. Transmission of process variables, which are necessary inĪpplications such as temperature and pressure control. The HART interface allowsįeatures such as remote calibration, fault interrogation, and Keyed (FSK) signal is modulated on top of the standard 4 mA to 20 mA analog current signal. HART is a digital 2-way communication in which a 1 mA peak-to-peak frequency shift The instrument communicates via aĤ mA to 20 mA analog output and a highway addressable Such as temperature (Pt100, Pt1000, and thermocouple) or bridge pressure sensors. The circuit shown in Figure 1 is an isolated smart industrial field instrument that interfaces to many types of analog sensors Because RTDs have an accuracy of better than 0.1☌ and repeatability, they are slowly replacing thermocouples in industrial applications below 600☌. A PT100 sensor is also relatively immune to electrical noise and therefore well suited for temperature measurement in industrial environments, especially around motors, generators, and other high voltage equipment. Most standard PT100 sensors comply with the DIN IEC Class B standard. Not only does it provide good accuracy, it also provides excellent stability and repeatability. The PT100 is one of the most popular and accurate RTD sensors. Platinum is a noble metal and has the most stable resistance-temperature relationship over the largest temperature range and is therefore more common than copper or nickel RTDs. They have been used for many years to measure temperature in laboratory and industrial processes, and have developed a reputation for accuracy, repeatability, and stability. RTDs contain a resistor that changes resistance value as its temperature changes. temperature relationship and an operating temperature range of –200☌ to +850☌. Made from either platinum, copper, or nickel, RTDs have a repeatable resistance vs. An RTD, or resistance temperature detector, is a sensor used to measure temperature.
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