PIC + type K - Electronic Circuits Projects Diagrams Free

trexter711 · 15th September 2007, 11:44 AM

Hello everyone. I'm just wondering if I can use a type K thernocoupler direct with any PIC.

Thanks

**Nigel Goodwin** · 15th September 2007, 11:48 AM

Almost certainly not, you need to amplify the output a LOT to make it large enough.

aljamri · 15th September 2007, 01:15 PM

sinc k-type has a range of (-200 °C to +1200 °C) as per: http://www.picotech.com/applications/thermocouple.htm
l
you may use PT-100 if its range is suitable ( -200°C to +850°C ) see :
http://www.maxim-ic.com/appnotes.cfm/an_pk/3450.

Sceadwian · 16th September 2007, 02:08 AM

If you want quick and dirty, a simple opamp to amplify the signal will work enough to give a PIC's ADC something to work with. But you better be a damn good programmer and signal analyst to make any degee of precision from it.

trexter711 · 16th September 2007, 07:41 AM

Thank you for your fast reply. I read somewhere (I don't recall...) that there's a pic that can handle type k thermocouple. I searched on "www.microchip.com" but nothing there about this subject. Anyone knows about it?

Eclipsed · 16th September 2007, 08:51 AM

The MAX6675 is probably the easiest/most accurate way of using a K type with a microcontroller.

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3149

mvs sarma · 16th September 2007, 01:58 PM

Quote:

Originally Posted by trexter711

Hello everyone. I'm just wondering if I can use a type K thernocoupler direct with any PIC.

Thanks

i an posting a PIC design document of temp sensors. on page 10 you find k-type thermocouple.

aljamri · 16th September 2007, 03:15 PM

Quote:

Originally Posted by mvs sarma

i an posting a PIC design document of temp sensors. on page 10 you find k-type thermocouple.

Thats a great document, whats the adress to get simillar document for another sensors.

Thanks

mvs sarma · 16th September 2007, 07:39 PM

It is downloaded from www.microchip.com directly

Oznog · 17th September 2007, 03:55 AM

There are ADCs like the LTC2418 that handle thermocouples fine.

A normal op-amp won't work well no matter how good a programmer you are!
The problem is offset, thermocouple inputs are so small that common opamp offsets might make hundred of degrees F of error.

Second thing here- is this thermocouple grounded? It's ok to do that, not only we can bolt both wires to a grounded cylinder head, in fact a thermocouple can even measure a temp on a grounded hot plate by bonding one wire at one point and the other wire at a different point! But this means one voltage is slightly above ground, the other slightly below, so we need to be able to measure slightly below ground AND we need to be differential.

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15th September 2007, 11:44 AM	(permalink)
trexter711	PIC + type K Hello everyone. I'm just wondering if I can use a type K thernocoupler direct with any PIC. Thanks

15th September 2007, 11:48 AM	(permalink)
Nigel Goodwin	Almost certainly not, you need to amplify the output a LOT to make it large enough. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

15th September 2007, 01:15 PM	(permalink)
aljamri	sinc k-type has a range of (-200 °C to +1200 °C) as per: http://www.picotech.com/applications/thermocouple.htm l you may use PT-100 if its range is suitable ( -200°C to +850°C ) see : http://www.maxim-ic.com/appnotes.cfm/an_pk/3450. __________________ Its what your friend in Your mind, what you in your friends mind

16th September 2007, 02:08 AM	(permalink)
Sceadwian	If you want quick and dirty, a simple opamp to amplify the signal will work enough to give a PIC's ADC something to work with. But you better be a damn good programmer and signal analyst to make any degee of precision from it. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

16th September 2007, 07:41 AM	(permalink)
trexter711	Thank you for your fast reply. I read somewhere (I don't recall...) that there's a pic that can handle type k thermocouple. I searched on "www.microchip.com" but nothing there about this subject. Anyone knows about it?

16th September 2007, 08:51 AM	(permalink)
Eclipsed	The MAX6675 is probably the easiest/most accurate way of using a K type with a microcontroller. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3149

16th September 2007, 07:39 PM	(permalink)
mvs sarma	It is downloaded from www.microchip.com directly __________________ Regards, Sarma.

17th September 2007, 03:55 AM	(permalink)
Oznog	There are ADCs like the LTC2418 that handle thermocouples fine. A normal op-amp won't work well no matter how good a programmer you are! The problem is offset, thermocouple inputs are so small that common opamp offsets might make hundred of degrees F of error. Second thing here- is this thermocouple grounded? It's ok to do that, not only we can bolt both wires to a grounded cylinder head, in fact a thermocouple can even measure a temp on a grounded hot plate by bonding one wire at one point and the other wire at a different point! But this means one voltage is slightly above ground, the other slightly below, so we need to be able to measure slightly below ground AND we need to be differential. __________________ I thought what I'd do was I'd pretend I was one of those deaf-mutes.