Solar water heater temp sensors? Buy where?

If you are designing the circuit there's nothing cheaper than diodes:

Tape them to the pipe under the insulation. The TO-220 package makes better thermal contact.

Transistor base-emitter junctions work fine too.

jsw

Try the auto parts store. They have thermistor based sensors in a good brass screw in package. I use the one with a 1/8" thread (Jeep) in a

1/2" bushing so you have enough meat for threads to mount a spade connector for the common lead. They can be very accurate if you use a whetstone bridge feeding an op amp (LM324) with a pot on the matching leg and a couple 10k resistors for the other legs

There are I2C and similar digital output sensors that are quite cheap.

You can make use of the car coolant temperature sensor and connect it to your controller.... no need to redesign the wheel ....

Can you suggest an appropriate one? Asking the counter clerk to help engineer a project isn't always very productive. =BFAlguien habla Ingl=E9s?

jsw

I use this one on my spa controller The plot I got for the Omix-ADA # 476801 (replaces 3177594) the numbers on the box

750 ohm @ 62f 468 @ 83f 403 @ 90f 342 @ 98f 324 @ 100f

There may be some variation between units but this should get you in the ball park.

I suspect most automotive units are roughly the same. This one said it was for a Jeep and I was using one for a Ford before but the threads were 1/2" requiring a trick to hook up the ground. (I used a ground rod clamp but it was ugly)

delphi packard eletric system PART NUMBER 12146312

Thanks

If I drove up in my 20 year old pickup and asked for a Buick Park Avenue part they might mistake me for a mechanic and give me a discount.

jsw