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ELCouz
Joined: 18 Jul 2007
Posts: 427
Location: Montreal,Quebec
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| High temperature sensor to interface with PIC |
 Posted: Wed Aug 03, 2011 4:02 pm |
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Dear electronic masters  ,
Another advice request! yay!
I need to measure fluid temperature (engine oil to be precise) with a pic.
What sensor is capable doing -40C/-40F to +200C/392F and is the most easier to implement ?
NTC Thermistor and thermocouple look hard to do (calibration needed and complex formulas)...
If you have code example to show how it works that would be very nice! 
many thanks!
EDIT: i think digital thermometer are out of question most of them goes only to +125C/257F like the famous DS18B20
_________________
Regards,
Laurent
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Here's my first visual theme for the CCS C Compiler. Enjoy! |
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ezflyr
Joined: 25 Oct 2010
Posts: 1019
Location: Tewksbury, MA
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| Posted: Wed Aug 03, 2011 5:48 pm |
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Hi,
I just completed a project using the new Maxim MAX31855 thermocouple-to-digital converter IC. This IC utilizes an SPI-like interface, and is super easy to get working with a PIC and CCS C. A number of different parts are available, each optimized for a particular thermocouple type. The stated accuracy for the -200C to +700C range of the type 'K' part is +/- 2C. I used a commercial thermocouple calibrator to calibrate my device over a range of -50C to +125C, and obtained +/- 0.1C accuracy.
John |
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temtronic
Joined: 01 Jul 2010
Posts: 9241
Location: Greensville,Ontario
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| Posted: Wed Aug 03, 2011 6:13 pm |
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I'd go with the digital( DS18B20). Easy to physically connect, easy to interface, to read/program. Especially when run in parasitic mode (2 wires)
It is very, very unlikely that you'll get oil up to 400*F unless we're not talking about monitoring a normal car engine. They typically run around 210-220*F coolant temp, oil is always a bit lower. The -40 spec is a wee bit low too. Anyone running down there will have block heaters on 24/7 !
Do some trials and see what you get. Add a 'thermocouple well' into the system so that you can test various sensors easily. Report back with the max temperature readings when you're done, should be interesting. |
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bkamen
Joined: 07 Jan 2004
Posts: 1615
Location: Central Illinois, USA
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| Posted: Thu Aug 04, 2011 5:53 am |
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| ezflyr wrote: | Hi,
I just completed a project using the new Maxim MAX31855 thermocouple-to-digital converter IC. This IC utilizes an SPI-like interface, and is super easy to get working with a PIC and CCS C. A number of different parts are available, each optimized for a particular thermocouple type. The stated accuracy for the -200C to +700C range of the type 'K' part is +/- 2C. I used a commercial thermocouple calibrator to calibrate my device over a range of -50C to +125C, and obtained +/- 0.1C accuracy.
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Ooo, they have a new one like the MAX6675? I have to check that out.
(that always bothered me that the 6675 only went down to 0'C)
-Ben
EDIT: I see they're discontinuing the MAX6675.. this is a much nicer part. I wish they had this out a long time ago!
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D |
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ELCouz
Joined: 18 Jul 2007
Posts: 427
Location: Montreal,Quebec
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| Posted: Thu Aug 04, 2011 8:21 am |
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thanks for all your reply
| Quote: | | It is very, very unlikely that you'll get oil up to 400*F unless we're not talking about monitoring a normal car engine. They typically run around 210-220*F coolant temp, oil is always a bit lower. The -40 spec is a wee bit low too. Anyone running down there will have block heaters on 24/7 ! |
The engine is not water cooled , its a air-cooled engine head temperature can rise up to 380F (now start to overheat)
| Quote: | | The -40 spec is a wee bit low too. Anyone running down there will have block heaters on 24/7 ! |
We can get this low on outdoor temp during winter but normally its around -30C/-22F
| Quote: | | Maxim MAX31855 thermocouple-to-digital converter IC |
You calibrate the chip thru SPI or you adjust the outputting values from this chip inside the PIC?
Other question when we talk about K type.... every K type mean it passed a measuring standard ? Does all K type thermocouple behave the same or i need one that can do negative temperature too?
On wikipedia i fail to see K type as a potential negative temperature sensor (short term maybe??)
thanks again! 
_________________
Regards,
Laurent
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Here's my first visual theme for the CCS C Compiler. Enjoy! |
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ELCouz
Joined: 18 Jul 2007
Posts: 427
Location: Montreal,Quebec
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