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I have an idea for a project, which needs to be able to measure temperatures up to 260°C. The accuracy is not crucial (±5°C is fine) but it is important that it can measure lower temperatures too.

I initially thought of using a silicon diode such as the 1N4148 as forward voltage is proportional to temperature with a nice linear slope of -2.1mV/°C. The current will be <100µA.

However, it looks like these diodes cannot survive a temperature this high, although it is not specified exactly what failure might occur. Can I expect the silicon die to break down and not work properly at this temperature, even though the current is low? The environment will be 260°C for 3-10 minutes, so it looks like any soldering rating is irrelevant.

If this does not work, what other low cost options are there for measuring high temperatures?

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    \$\begingroup\$ Have you googled "thermocouple" yet? \$\endgroup\$ – The Photon Jan 21 '12 at 1:24
  • \$\begingroup\$ @The Photon I did consider thermocouple, but that would involve a thermocouple amplifier, which isn't necessarily cheap. Then again, it may be the only option. \$\endgroup\$ – Thomas O Jan 21 '12 at 9:52
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Forget the diode - for this temperature you would need either a thermocouple or an RTD.

You can get either type suitable for what you want to do for a few pounds, check on places like Farnell, Mouser, etc under temperature sensors.

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