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( File format: PDF, 251 Kbytes )
Precision Fahrenheit Temperature Sensor
National Semiconductor

Description
The LM34 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Fahrenheit temperature. The LM34 thus has an advantage over linear temperature sensors calibrated in degrees Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Fahrenheit scaling. The LM34 does not require any external calibration or trimming to provide typical accuracies of ?F at room temperature and 1?F over a full -50 to +300F temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM34's low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with single power supplies or with plus and minus supplies. As it draws only 75 ?A from its supply, it has very low self-heating, less than 0.2F in still air. The LM34 is rated to operate over a -50 to +300F temperature range, while the LM34C is rated for a -40 to +230F range (0F with improved accuracy). The LM34 series is available packaged in hermetic TO-46 transistor packages, while the LM34C, LM34CA and LM34D are also available in the plastic TO-92 transistor package. The LM34D is also available in an 8-lead surface mount small outline package. The LM34 is a complement to the LM35 (Centigrade) temperature sensor.
Features

???Calibrated directly in degrees Fahrenheit
???Linear +10.0 mV/F scale factor
???1.0F accuracy guaranteed (at +77F)
???Rated for full -50 to +300F range
???Suitable for remote applications
???Low cost due to wafer-level trimming
???Operates from 5 to 30 volts
???Less than 90 ?A current drain
???Low self-heating, 0.18F in still air
???Nonlinearity only 0.5F typical
???Low-impedance output, 0.4Ohm for 1 mA load




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