The best temperature sensor for water...

[Jin Jia G8]

I am a student who start doing NI project about water heater..

which sensor will be suitable for hot water, I gotta try that out.

thanks

[RavensFan]

What kind of hardware do you have to read the sensor?

Thermocouple, thermistor, and RTD are 3 of the most common.  Thermocouples require special signal conditioning to read the millivolt signals they output.  They also need a temperature measurement (usually a thermistor) to account for voltages generated at the cold junction but that can also be compensated in calculations if you assume a temperature such as room temperature. 

Thermistors and RTD's require a means to measure a resistance.  This means signal conditioning such as a Wheatstone bridge to convert resistance to a voltage measurement, but this is also often in the millvolt or fraction of a volt range.

[Henrik_Volkers]

Questions :

Needed temperature range: 0°C-100°C, or under pressure up to 400°C??

Needed resolution and accuracy?

How fast is the temperature change, and how fast must the sensor be? 

TCs could be very fast, RTD range from fast to quite slow, NTC are like RTD . Mostly a function of sensor construction

Water is a good thermal conductor and one of the mediums with the highest thermal capacity, so maybe the step response of the sensor doesn't matter 😉

 Mechanical ,

waterproof ?? 

Stiffness? (flowing water?)

size?? Small coffee maker heater or 1000l tank => small sensor needed? 

Shielded sensor or completely floating? I have seen direct (electrical) 3 phase water heaters, the current is flowing through the water to heat it, bad idea to use a grounded sensor 😉 

Budget?? (Answered: student => 0 😉  )

You see, the answer to the best sensor needs the best question(s) (including the most specific requirements).

You can have it: QUICK, CHEAP and GOOD

Pick two