Temperature sensing project - Page 1
Forum section: electronics / projects

author: pinank
author_rank: Newbie
timestamp: May 31, 2014, 05:24:35 am
content: I have project on sensing temperature of a liquid flowing through a tube of 15mm diameter. I searched for various thermostats for about that size but can't find any. Can anyone suggest me any method to sense temperatures for this project? Also I saw Dave Jones video on the teardown of 1200W rack power supply. They used a very small thermostat to sense the temperatures of full bridge rectifiers. Pls someone elaborate on it.Thank you for helpSent from my Nexus 4 using Tapatalk

author: David_AVD
author_rank: Super Contributor
timestamp: May 31, 2014, 06:01:49 am
content: What about a thermocouple as the sensor? Make sure you chose one suitable for liquid immersion.

author: pinank
author_rank: Newbie
timestamp: May 31, 2014, 07:05:40 am
content: Can u send me some link?Sent from my Nexus 4 using Tapatalk

author: branadic
author_rank: Super Contributor
timestamp: May 31, 2014, 07:46:24 am
content: Have a look on this AppNote, what you further need is an adaqute heater and a good thermal interface between the PT1000 elements and your fluid:www.etracker.de/lnkcnt.php?et=UKbtw3&url=http://www.acam.de/fileadmin/Download/pdf/TDC/English/AN024_en.pdf&lnkname=AN024_en

author: SeanB
author_rank: Super Contributor
timestamp: May 31, 2014, 12:35:20 pm
content: Basically a NTC thermistor in a metal case tied to the pipe, and covered with some Isotherm foam jacket so that it is not influenced by air temperature. Same as used on TXV in airconditioning where you need to sense the temperature of a liquid refrigerant in a pipe.

author: dannyf
author_rank: Super Contributor
timestamp: May 31, 2014, 03:09:26 pm
content: A diode would work as well, depending on your application.

author: CrabxCore
author_rank: Contributor
timestamp: May 31, 2014, 03:11:35 pm
content: What sort of temp range are you estimating?

author: David_AVD
author_rank: Super Contributor
timestamp: May 31, 2014, 10:00:03 pm
content: Quote from: pinank on May 31, 2014, 07:05:40 amHere you go.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 31, 2014, 10:29:18 pm
content: I've had great luck with a diode connected 2N3904 (connections sealed with hot glue and heat shrink) taped to the pipe with foil tape, then insulated with foam tape. To digitize the temperature readings, I use a TI TMP513. The readings are so accurate that in a HVAC application, the pressure measurements derived from it (look up PT chart to understand how that works) are more accurate than the pressure gauges often used for that task!

author: dannyf
author_rank: Super Contributor
timestamp: June 01, 2014, 02:07:02 am
content: Diodes have very consistent slope for the same process. But wild output voltage at a given temperature, even if the devices are produced from the same batch. Very difficult to use without calibration.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 01, 2014, 02:26:32 am
content: The TMP513 claims to have +-1C accuracy with no manual calibration needed. In my experience, that's about right. From my understanding, it checks the voltage drop over several currents and uses that to automatically compensate.