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Embedding Temperature Information ADXL202's Outputs Harvey Weinbe
Top Searches for this datasheetAN-600 APPLICATION NOTE Embedding Temperature Information ADXL202's Outputs Harvey Weinberg INTRODUCTION Many cases exist where it's important know temperature ADXL202. Sometimes temperature information necessary control data logging requirements data loggers used monitor articles handled shipping) high precision tilt sensor applications (for temperature compensation zero drift accelerometer). Since converter required when using ADXL202's duty cycle outputs, preferable have some means acquiring temperature information digitally. This application note outlines simple method embedding temperature information from TMP36 voltage output temperature sensor duty cycle acceleration output ADXL202. converter required, additional necessary. BASIC PRINCIPLE OPERATION duty cycle output period proportional current flowing through RSET. voltage typically 1.25 recommended range RSET resistor (125 1.25 current Normally RSET connected between ground, noise free voltage source between 1.25 acceptable. Figure TMP36 voltage output temperature sensor connected RSET. TMP36 output voltage RSET 127k OUTPUT CASES SHOWN PERIOD 1355 PERIOD 1855 PERIOD 2915 XOUT YOUT TMP36 RSET MICROCONTROLLER ADXL202 RSET YFILT XFILT Figure Using Temperature Sensor Embed Temperature Information into Acceleration Duty Cycle Output ADXL202 most applications, period need measured every cycle (this discussed thoroughly "Using ADXL202 Duty Cycle Output" application note). Since temperature change normally speed phenomenon, this will affect accuracy temperature measurements. Measuring period times second should more than sufficient. subroutine used determine temperature from period must added user's firmware. Since change completely linear over temperature, subroutine's complexity will vary proportion temperature accuracy required. Table shows typical period versus temperature. Using simple calculation 0.75 (0.01 Volts where temperature Over range -40°C +70°C, output resulting current RSET 1.25 1.25 RSET RSET RSET Temperature 1735 Using resistor RSET, current over -40°C +70°C temperature range. where Temperature This technique will result temperature readings that accurate ±5.5°C over range -20°C +40°C. more accurate REV. Analog Devices, Inc., 2002 AN-600 temperature readings required, simple look-up table used. Alternatively, both initial constant (1735) divisor (26) modified higher accuracy over narrower temperature range. Table Temperature Circuit Figure Temp. (°C) 1250 1300 1355 1420 1490 1565 1650 1740 1855 1980 2110 2280 2450 2660 2915 3230 3620 Calculated Temp. -18.7 -16.7 -14.5 -12.1 -9.4 -6.5 -3.3 +0.2 +4.5 +9.5 +14.4 +27.5 +35.6 +45.5 +57.5 +72.5 example, consider shipping conditions recorder item that must kept 10°C 1°C. From Table that 10°C produces period 1855 Assuming that interested high accuracy over 15°C range, that period changes from 1980 15°C 1740 5°C. Therefore assume that change 1980 1740 15°C then modify temperature equation Temperature 1855 which will accurate ±0.2°C over 15°C range. REV. PRINTED U.S.A. E03045-0-7/02(0) Other recent searchesTSC80C31 - TSC80C31 TSC80C31 Datasheet RJ-6 - RJ-6 RJ-6 Datasheet NT5DS16M16CS - NT5DS16M16CS NT5DS16M16CS Datasheet NT5DS32M8CS - NT5DS32M8CS NT5DS32M8CS Datasheet NT5DS16M16CG - NT5DS16M16CG NT5DS16M16CG Datasheet CPT-18-8004 - CPT-18-8004 CPT-18-8004 Datasheet BAT40VC - BAT40VC BAT40VC Datasheet 2SJ381 - 2SJ381 2SJ381 Datasheet
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