Monitoring temperatures inside a solar thermal (hot water) collector?

I’m planning on building a DIY solar collector for domestic hot water, and I’d like to remote-monitor the temperatures inside it.

Do you think a emonTH with 4x encapsulated DS18B20 sensors would be suitable? I was thinking of taping a sensor to the incoming (cold) water pipe, outgoing (hot) water pipe, the aluminium heat spreader plate, and buried inside the insulation.

I don’t really know how hot the inside will get, but I think the sensors work up to +125C ? Is there an alternative sensor that can take even higher temps?

Also, is the standard emonTH case waterproof? I want to attach it to the outside of the solar collector so I can easily change batteries.

Many thanks

The emonTH case has ventilation slots for the internal temperature and humidity sensor to work, so definitely NOT waterproof. The sensors are indeed specified up to 125 °C, but with reduced accuracy.

Maxim don’t appear to offer a 1-wire sensor going higher than that, so for the non-water sensors, you might need to consider something like Pt100, but you’d need to develop an interface for it (see Building Blocks for an Arduino interface, and don’t be put off by the table - Pt100 sensors can go far higher than that suggests, about 600 °C). You might not need the multiplexer (depends on how many ‘high temperature’ points you need to measure) but battery life could be a problem unless you switch the power to the interface and only check temperatures occasionally (every few minutes).