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Temperature sensor to put into water

koudelad

Hello,

 

I would like to ask for recommendation of a temperature sensor to put into water. I have two household (amateur) applications in mind, one for drinkable and one for non-drinkable water. Temperature range is between ca. -10 and +120 centigrade, precision needed ca. +/- 1 centigrade. Something with a one or two meter cable would be perfect.

 

I was thinking about some DIY variant, but I am afraid of adding unnecessary thermal capacity to the sensor and shifting the original scale off. Last time I used LM75A LM335, just the non professional solder joints shifted the measured value to ca. -4 centigrade.

 

Thank you,

David

 

EDIT: I meant analog output LM335.

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  • I've always stayed away from using analogue sensors.

    One reason is the scale is not always linear ... well at least in the product I fixed with them in.

     

    I tend to always head to the DS18B20 with it's waterproof connection.

    Terry has them on sale at the moment.

    Waterproof DS18B20 stainless steel encapsulated temperature sensor 1M Cable

     

    Your +120 C will be difficult without containing the pressure as said.

    You can use a gland nut to tighten around the body, and I've seen the unprotected version (with a good blob of thermal transfer paste) fitted into a probe which was sealed.

     

    The thermal mass is not going to be an issue as you're measuring water, and unless you're trying to detect temperatures in small flows, it will follow the water temperature with very little lag.

     

    Mark

  • in reply to mcb1

    Thank You, Mark.

     

    You are both right. For now it's enough if the sensor and it's case withstand 100 C maximum - this will be used at home.

     

    I also had one application in mind where I would measure an engine coolant temperature, but I could also try to measure higher temperatures from the "dry side". I will postpone this until I have more time.

     

    David

  • in reply to koudelad

    There is a high temp version of the DS18B20.

  • in reply to koudelad

    where I would measure an engine coolant temperature

    I've done one of these and I used an "off the shelf" sensor and mapped the temperature spots I was interested in.

     

    Here is the closest I get to cooking.

    imageimage

     

    I did it this way because trying to seal the sensor would be a problem and with the engine bay temperatures, plastic (gland nuts) wasn't going to stand a chance.

     

     

    If I was going to repeat it, I'd consider inserting a pipe into the radiator hose and weld a sealed tube into the water flow, thereby creating a watertight and pressure tight interface.

     

     

    You can also buy these (this was from Australia). it is intended to provide a threaded fitting.

    image

    Mark

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  • in reply to koudelad

    where I would measure an engine coolant temperature

    I've done one of these and I used an "off the shelf" sensor and mapped the temperature spots I was interested in.

     

    Here is the closest I get to cooking.

    imageimage

     

    I did it this way because trying to seal the sensor would be a problem and with the engine bay temperatures, plastic (gland nuts) wasn't going to stand a chance.

     

     

    If I was going to repeat it, I'd consider inserting a pipe into the radiator hose and weld a sealed tube into the water flow, thereby creating a watertight and pressure tight interface.

     

     

    You can also buy these (this was from Australia). it is intended to provide a threaded fitting.

    image

    Mark

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