temperature sensor for aquarium

[aliyesami]

i am looking to build a temperature sensor for my salt water aquarium where the temperature might change from 75 deg C to 90 deg C .
which sensor I can use in TO-93 package that can give me less than 1 deg accuracy ?
in aquariums even 1 or 2 deg change makes a lot of difference in coral growth an health so i need very accurate measurement of the water temperature.

thanks

 

[FvM]

I presume you mean 75 to 90 degree F rather than degree C?

 

[aliyesami]

yes sorry .. I meant deg F

 

[betwixt]

If you want analog voltages to represent the temperature, look at LM35, MCP9700/9701.
If you want two wire I2C serial readings, try TCN75. (needs more pins so not in TO-92)
For one-wire serial readings try DS18B20 or DS18S20.

Brian.

 

[aliyesami]

yes I need analog voltage and I looked at LM35 and other similar chips they all have accuracy of +-3 to +-4 degree C , what does that mean exactly and how will it effect me when I want to measure the water temp with accuracy of less than a degree ?

 

[FvM]

LM35 accuracy at 25 to 35 °C is considerably better, for higher accuracy requirements you'll either calibrate the sensor or use a sensor with better initial accuracy, e.g. Pt100.

 

[betwixt]

Agreed, there are two kinds of inaccuracy at play here, one is the linearity and the other is absolute reading. The linearity shouldn't be a problem, it is a measure of how much DIFFERENCE there is between the voltage returned for 1 degree change when near its cold limit and 1 degree near it's hot limit, as you are measuring over a small range it will be insignificant. The absolute measurement is the one that might be different from one sensor to the next but it's easy to trim out the error as it will be a constant.

Brian.