Resistive temperature devices

Monitor temperature of material being dried by infrared, resistance temperature device, (RTD) etc. 

The DieMate manifold also functioned as the microreactor die heater since it had four driUed-through holes to accommodate %-inch-o.d. cartridge heaters where each provided 15 watt of power (60 W total). The holes are visible adjacent to the O-rings in Fig. 12.3. The temperature of the DieMate manifold was monitored using two 1 /16-inch-o.d. X 1-inch 100 O platinum Resistive Temperature Devices (RTDs). 

A flexible Kapton -coated heater is wrapped aroimd the clamshell and is powered using a 24 VDC input. The temperature of the clamshell is monitored using two 100 O platinum Resistive Temperature Devices (RTD s). Both the DieMate manifold and the clamshell heater are insulated using ceramic fiber strip obtained from a commercial source with a maximum temperature rating of 2300 F. 

Thermal measurements include heater power, and temperatures of rock, air, water, and at various other surfaces. Rock temperatures are measured by both resistance temperature devices (RTDs) and thermocouples. The RTDs are grouted in holes drilled into the rock to house them. Figure 2 shows the RTD holes in the DST. Thermocouples are attached to surfaces such as the drift wall, wing heaters, cable-trays etc. 

While temperature transmitters are checked and calibrated, sensors may not be checked directly. The operation of some, notably those on the outlets of the electrolyzers, cannot be verified by liquor circulation before startup. A common assumption is that thermocouples (T/Cs) and resistance temperature devices (RTDs) work correctly. If desired, they can be checked by a hot box, if one is available, or by immersion in a flask of hot water or other appropriate fluid. A hot box is a dry-heated temperature-controlled block with drilled holes to accept RTD or T/C sensors. No further calibration of the instrument is necessary after installation, and the DCS indication should be checked against a thermometer of known accuracy. 

Heat flux sensors to measure heat flow between the ground and the dispersing cloud were located on the desert surface at locations in the downwind arrays. Type K thermocouples were positioned on the downwind array towers to measure cloud temperature as it moved downwind. Multiple levels of thermocouples were located just upwind of the spill point, as well as four resistive temperature devices (RTD), one defined as Ihe absoluie temperature (0.5-m height) and three to provide delta temperature measurements relative to the absolute reading (1, 2, and 4 m). 

Many types of sensors and transducers have particular signal conditioning requirements. For example, thermocouples require cold-junction compensation for the thermoelectric voltages created where the thermocouple wires are connected to the data acquisition equipment. Resistive temperature devices (RTDs) require an accurate current excitation source to convert their small changes in electrical resistance into measurable changes in voltage. To avoid errors caused by the resistance in the lead wires, RTDs are often used in a 4-wire configuration. The 4-wire RTD measurement avoids lead resistance errors because two additional leads carry current to the RTD device, so that current does not flow in the sense, or... 

In the process industries often a thermocouple or resistive temperature device is used. However, submerging it directly into the gas or liquid could damage the device. Therefore often a thermowell, as shown in Fig. 31.12, is used for protection. 

RTD - Resistance temperature device a sensor that measures temperature by a change in resistance as a function of temperature. 

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