How to measure the power consumed by a temperature sensor theoretically?

The datasheets mention the supply voltage range and output current. So, to calculate the power supply current will be used in P=VI. The supply current is not mentioned in the datasheets. What is the way to calculate this value?

The supply current will depend on the resistance.

  • The datasheets mention a number of thermal resistance value. Is there any relation between these resistance values?
  • and will this information help in finding out the power consumed?
  • If the temperature sensor is being used for continuous monitoring, does the power consumption vary?
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    \$\begingroup\$ you'll have to tell us what kind of sensor you're talking about. There's many ways of building a temperature sensor! (In fact, an old EE saying goes: every component is a temperature sensor, some just also happen to fulfill other purposes, because basically everything in electronics varies with temperature to some extent) \$\endgroup\$ – Marcus Müller Dec 9 '18 at 11:02
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    \$\begingroup\$ So, since your sensor seems to be a relatively complex device, it certainly has a type number or even a datasheet. Without that, we can't help you. \$\endgroup\$ – Marcus Müller Dec 9 '18 at 11:05
  • \$\begingroup\$ Power consumption depends on the temperature.. LOL \$\endgroup\$ – Linkyyy Dec 9 '18 at 11:37
  • \$\begingroup\$ @MarcusMüller Thank you. I am using LM35 which is analog type. \$\endgroup\$ – Megh Dec 9 '18 at 12:36
  • \$\begingroup\$ @Linkyyy what's so funny? \$\endgroup\$ – Marcus Müller Dec 9 '18 at 14:02

If the sensor is digital one you should have in the datasheet a "Conversion Time vs Temperature" graph. In the datasheet also you can see the current consumption in shutdown mode (0.5 - 1 uA) and active mode (10 - 12 uA). Depending on how often you measure the temperature you can compute the power consumption.

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  • \$\begingroup\$ Thank you. I am using analog type LM35. \$\endgroup\$ – Megh Dec 9 '18 at 12:34
  • \$\begingroup\$ @Megh this answers your question, doesn't it? 10-12 µA · supply voltage. So, accept this answer? \$\endgroup\$ – Marcus Müller Dec 9 '18 at 14:02
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    \$\begingroup\$ IIf you have a LM35 then the quiescent current has a higher magnitude (at 5V, 25 degrees Celsius around 50 - 55 uA). To clarify this : quiescent current is the current that LM35 draws on its own. The output current depends on your load, in datasheet is listed only the maximum load current (10 mA). So the power consumption is (55 uA + IL ) * supply voltage. \$\endgroup\$ – pantarhei Dec 9 '18 at 14:23
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    \$\begingroup\$ Also depends on the environment temperature. 55uA is the quiescent current for 25 degrees C. If the temperature varies from 25 up to 125 then you should consider that the quiescent current at 125 is around 100 uA. \$\endgroup\$ – pantarhei Dec 9 '18 at 14:29
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    \$\begingroup\$ @Megh you have to check in the datasheet A/D Converter characteristics. \$\endgroup\$ – pantarhei Dec 9 '18 at 14:33

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