Temperature sensing technologies

Is there a "safe" way of talking to the one-wire devices over long lengths of wire? E.g., could I put one on the end of 30 feet of "cable" and expect it to operate reliably?

I've only seen them used in relatively benign situations...

That was the initial "integrated" sensor that I had considered. The LM134 that piglet and Jim have mentioned seems like it should be a step up (in terms of "amount of signal").

I'm concerned that you've had failures from (nearby?) lightning strikes, though. Are the cables entirely indoors? Or, are you running them out to the back porch ("outdoor temperature sensor"), etc.

I'd eventually like to calibrate one of sensors for monitoring outdoor temperature ("local weather station") and your experience has me worried about durability...

ISTR Jan P. or someone else in europe claiming to have instrumented their house with 1-wire sensors several years back.

They only require two conductors for connection, so, use a balanced pair and keep the sensors isolated from local grounds.

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OK, ALL the sensors that failed were on my furnace. We have a hydronic system, so there are pipes with hot water that spread out to 3 zones. I monitored the temp of those pipes by strapping the TO-18 sensor to the pipe. When the failures happened, I put a piece of Bergquist TO-220 thermal pad under the sensor, and no more failures. So, it was a loop of two conductors developing a serious voltage. We are near the top of a ridge, and occasionally get some very close strikes. We've even had an ethernet port blown out, which is surprising as they have pretty good galvanic isolation. I built my own burglar/fire alarm system, and it got seriously fried. So, as long as the metal case of the TO-18 package is not electrically connected to something, the sensors seem to be robust.

Jon

But, that's just coincidence (not significant in the diagnosis; they could just as easily have been on the municipal water main or an HVAC duct (if you had those)?

"replacement"

But, isn't the heating system effectively grounded? E.g., we had hot-water heat growing up. There was copper (or the cast iron water jacket of the furnace) connecting every point to earth, eventually.

Or, do you think you see enough of a ground bounce from those strikes to have caused the problem? Whereas the (isolated by your power supply) replacement sensors had a tad bit more of a surge suppressor between them and the true ground?

I am actually surprised that more ethernet ports -- even in relatively benign environments -- aren't fried in the normal course of use. I've inserted a "buffer" between each port and the switch (think of it as a one port firewall with EXTRA galvanic isolation and lightning protection) in anticipation of these sorts of problems (as well as an added defense against hostile actors -- wouldn't want your security system to be compromised by some guy with a hand-held Tesla coil!).

[I have drops exposed on the front and back porches, inside the garage, at IP security cameras, on the roof, etc.]

But, the *wires* feeding it ARE connected to "something". You're just hoping

*THAT* is more immune from the strikes (?) I.e., if you'd grounded your electronics to the water pipe, would you expect a similar immunity? or vulnerability?

Or use a current loop.

32 expected Wednesday AM. Which means we'll be kissing 28 (point at which the trees/fruit get uncomfortable) -- but I'm sure it will only be for a fraction of an hour (local heating plus a good soaking of the soil -- even after tonight's rain -- should help with convective warming)

Four "Kelvin" connections... send in a current, measure a voltage. You can even do the delta Vbe vs current to get a rough calibration. I like the to-220 pack that has a built in hole for the mounting screw. Diodes are everywhere!

George H.

W1209 uses 10K NTC thermistor as a sensor. The board seem use STM8S003 MCU, which has 10-bit ADC.

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                              Waldek Hebisch