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Pocket: Using the LM335 Temperature Sensor
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Temperature  sensor  LM335  usage
8 weeks ago by arnoldn
How to Build a LM335 Temperature Sensor Circuit
In this project, we will demonstrate how to build temperature sensor circuit using a LM335 sensor. As a temperature sensor, the circuit will read the temperature of the surrounding environment and relay this temperature to us back in degrees Kelvin. The difference between an LM335 and LM34 and LM35 temperature sensors is the LM335 sensor gives out the temperature in degrees Kelvin, while the LM35 sensor gives out the temperature in degrees Celsius and the LM34 sensor gives out the temperature in degrees Fahrenheit. All 3 are calibrated different to output the millivolt voltage reading in proportional to these different units of measurement. The LM335 sensor outputs 10mV/°K. So if the LM335 is giving an output reading of 2.943 (which is 2943mV), then this is equivalent to a temperature of 294.3° Kelvin. All you have to do is take the output reading and divide it by 10 in order to get the temperature output reading. This output reading of 294.3° kelvin is equivalent to 70°F and 21.11°C.
lm335az  lm335  maker  diy  temperature  arduino  sensors
december 2014 by dlkinney
Interfacing LM335 to XBee ADC Pin - Electrical Engineering Stack Exchange
Set the potentiometer so that at 25°C you have 2.982V at the output. If you don't need the calibration just leave out the potentiometer. Your reading will be less precise. Uncalibrated error is for the LM335 typically 2K @25°C, maximum 9K(!) over the full range (table on page 2), so that you might prefer to calibrate it after all. The value of R1 must be chosen in function of the power supply; on the first page you can read that it needs between 400μA and 5mA. Suppose the maximum temperature you want to measure is 30°C (that's 303.15K). The output will then be 3.03V. The current through the potentiometer will be 3.03V10kΩ=303μA. You have a 3.3V power supply, then R1=3.3V−3.03V400μA+303μA=384Ω maximum. Being good designers :-) we now check if the current isn't going to be too high at the lowest temperature. Suppose we want to measure temperatures as low as 0°C, that's 273K, giving VOUT=2.73V. The resistor current will then be IR1=3.3V−2.73V384Ω=1.5mA, subtract the 273μA through the potentiometer, and we have 1.2mA through the LM335, way below the allowable 5mA, so that's OK. R1 has to be smaller than 384Ω if you want to measure higher temperatures. With a 3.3V supply your theoretically maximum measurable is 330K, or 57°C. In practice somewhat less, because you will always need some voltage over the resistor. The resistor value will be so low, however, that at lower temperatures you almost certainly will exceed the allowable 5mA. Connect VREF to VCC. National has also a sensor giving you the temperature directly in °C (LM35) and I thought this would be a solution for measuring higher temperatures (at 57°C it will only output 570mV, so you'd have enough headroom), but that needs at least 4V, so that wouldn't help us.
temperature  lm335  lm335az  maker  sensors  arduino  diy
december 2014 by dlkinney

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