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I used a normal room thermometer and place on top of the plug of a power adapter and I notice that the temperature display is hovering around 35 degree Celsius to 37 degree Celsius.

Is it safe? Should I replace the plug of the power adapter or should I change the power adapter or should I also change the electrical device that the power adapter is connecting to?

For your information:
The electrical device that was powered by the power adapter is 1.3A (DC 3.6V) while the power adapter is 2A (DC 3.5V)

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What's the room temperature in your area? The 35 C temperature looks very good to me. Some power supplies go up to 80 C when working fine. – AndrejaKo Jun 17 '12 at 12:28
As this is now it is purely a consumer electronics question because you are asking about the safe use of consumer electronics. We are about the design of electronics. – Kellenjb Jun 17 '12 at 16:41

closed as off topic by Kellenjb, Kortuk♦ Jun 17 '12 at 18:16

Questions on Electrical Engineering Stack Exchange are expected to relate to electronics design within the scope defined in the FAQ. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about closed questions here.

2 Answers

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37°C is only 99°F, which sounds safe enough for the outside. However, outside temperature isn't the best indicator of how safe something is. You want to make sure the inside temperature at heat source doesn't reach ignition of whatever material it is made of or is immediately around it.

As I already said in another answer to a very similar question of yours, check the device's rating and don't exceed it. Supposedly someone that actually knows what it inside and what the material's limits are has done the appropriate calculations and distilled the result down to a simple to follow current rating. Follow it, don't play games.

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Why did you measure the temperature? Because you felt it got hot? In that case the real temperature will most likely be higher than 36°C, which wouldn't feel hot at all. A room thermometer is designed to measure air temperature and is not fit for contact measurements. The thermal contact between enclosure and thermometer will be bad, so I think it won't give you a correct reading.

That being said, there's probably not a problem here. Older power adapters use linear regulators and those can dissipate some power and therefore become hot. Like Olin says, if you use the adapter within its specifications, you'll be safe. Then the raised temperature is accounted for in the design.

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