Applying the AD590 GENERAL APPLICATIONS 10kQ2 OFFSET AD590 AD707 AD2040 GAIN SCALING 5MS T1-T2)(10mV^c OFFSET SCALING 10k2 Figure 10. Variable Scale Display Figure 12. Differential Measurements Figure 10 demonstrates the use of a low cost Digital Panel Meter for the display of temperature on either the Kelvin, desired temperature difference. For example, the inherent offset between the two devices can be trimmed in If V+ and Celsius or Fahrenheit scales. For Kelvin temperature Pins 9, 4 V- are radically different, then the difference in internal nd 2 are grounded; and for Fahrenheit temperature Pins 4 and dissipation will cause a differential internal temperature rise 2 are left open. This effect can be used to measure the ambient thermal The above configuration yields a 3 digit display with 1 C or 1 F resistance seen by the sensors in applications such as fluid level resolution, in addition to an absolute accuracy of #2. C over detectors or anemometry the-55C to+125C temperature range if a one-temperature calibration is performed on an AD590K, L, or M. +15V REFERENCE IRON ONSTANTAN AD590 AD590 SAD D590 AD580 JUNCTION CAD590 METER o十 RESISTORS ARE 1%, 50ppm/C Figure 13. Cold Junction Compensation Circuit for Type J Thermocouple Figure 13 is an example of a cold junction compensation circuit Figure 11. Series Parallel Connection for a Type J Thermocouple using the AD590 to monitor the reference junction temperature. This circuit replaces an ice-batI Connecting several AD590 units in series as shown in Figure 11 as the thermocouple reference for ambient temperatures allows the minimum of all the sensed temperatures to be between +15C and +35.C. The circuit is calibrated by indicated. In contrast, using the sensors in parallel yields the adjusting Rr for a proper meter reading with the measuring average of the sensed temperatures junction at a known reference temperature and the circuit near The circuit of Figure 12 demonstrates one method by which +25C. Using components with the TCs as specified in Figure differential temperature measurements can be made. Rl and r2 13, compensation accuracy will be within +0.5C for circuit an be used to trim the output of the op amp to indicate a temperatures between +15C and +35.C. Other thermocouple types can be accommodated with different resistor values. Note that the TCs of the voltage reference and the resistors are the primary contributors to error REV. BREV. B –7– GENERAL APPLICATIONS Figure 10. Variable Scale Display Figure 10 demonstrates the use of a low cost Digital Panel Meter for the display of temperature on either the Kelvin, Celsius or Fahrenheit scales. For Kelvin temperature Pins 9, 4 and 2 are grounded; and for Fahrenheit temperature Pins 4 and 2 are left open. The above configuration yields a 3 digit display with 1°C or 1°F resolution, in addition to an absolute accuracy of ±2.0°C over the –55°C to +125°C temperature range if a one-temperature calibration is performed on an AD590K, L, or M. Figure 11. Series & Parallel Connection Connecting several AD590 units in series as shown in Figure 11 allows the minimum of all the sensed temperatures to be indicated. In contrast, using the sensors in parallel yields the average of the sensed temperatures. The circuit of Figure 12 demonstrates one method by which differential temperature measurements can be made. R1 and R2 can be used to trim the output of the op amp to indicate a Figure 12. Differential Measurements desired temperature difference. For example, the inherent offset between the two devices can be trimmed in. If V+ and V– are radically different, then the difference in internal dissipation will cause a differential internal temperature rise. This effect can be used to measure the ambient thermal resistance seen by the sensors in applications such as fluid level detectors or anemometry. Figure 13. Cold Junction Compensation Circuit for Type J Thermocouple Figure 13 is an example of a cold junction compensation circuit for a Type J Thermocouple using the AD590 to monitor the reference junction temperature. This circuit replaces an ice-bath as the thermocouple reference for ambient temperatures between +15°C and +35°C. The circuit is calibrated by adjusting RT for a proper meter reading with the measuring junction at a known reference temperature and the circuit near +25°C. Using components with the TCs as specified in Figure 13, compensation accuracy will be within ±0.5°C for circuit temperatures between +15°C and +35°C. Other thermocouple types can be accommodated with different resistor values. Note that the TCs of the voltage reference and the resistors are the primary contributors to error. Applying the AD590