One Wire Control? Thermocouples
TJHJ
Posts: 243
So Ive been looking at the one wire object, and I have a few questions, I am assuming this is to be used with the DS 2760 maxim, chip for use with a thermocouple.
How does it know what type of Thermocouple you are using? Because I cant see anywhere in the code where it does the calc to return the value in Deg C. But I think it has to somewhere... And each type has a different Coefficient set to calculate the V to Deg C.
Is the returned value a byte number? Wouldn't it have to be a word for it to be the actual temp? Or does it not return the temp in Deg C, back to question 1, interrelated confusing. And a 1400 Deg range roughly at 8 bit resolution seems pretty poor to me.
Does it compensate for the cold junction or does the chip do that?
Is there a setup or reference someone can point me to that would allow me to run more than one sensor one chip?
*Question to above, Can I use a ADC say the 8034, 4 channel, It would let me put 4 probes on each chip, I need 10 all are Type K. Or is the range change to small? I feel the prop would not have to hard a time pulling off the calc to convert it to a temp, considering I am planning on having one prop only doing this? Maybe Im looking at this wrong. Help, Ideas, Links?
Thanks as always for all the help.
TJ
How does it know what type of Thermocouple you are using? Because I cant see anywhere in the code where it does the calc to return the value in Deg C. But I think it has to somewhere... And each type has a different Coefficient set to calculate the V to Deg C.
Is the returned value a byte number? Wouldn't it have to be a word for it to be the actual temp? Or does it not return the temp in Deg C, back to question 1, interrelated confusing. And a 1400 Deg range roughly at 8 bit resolution seems pretty poor to me.
Does it compensate for the cold junction or does the chip do that?
Is there a setup or reference someone can point me to that would allow me to run more than one sensor one chip?
*Question to above, Can I use a ADC say the 8034, 4 channel, It would let me put 4 probes on each chip, I need 10 all are Type K. Or is the range change to small? I feel the prop would not have to hard a time pulling off the calc to convert it to a temp, considering I am planning on having one prop only doing this? Maybe Im looking at this wrong. Help, Ideas, Links?
Thanks as always for all the help.
TJ
Comments
Funny you ask this question. I was searching the forums not to long ago myself trying to find ways to read the DS2760 using the propeller chip, as we got a DS2760 kit from Parallax to use as a soil probe for our QuadRover.
Anyways what code are you looking at? If its just the one wire object, you are correct that code is not set up to read the DS2760, it simply just gives you the ability to communicate with a one wire device.
When I searched the forums for how to interface to the DS2760 I found this posting.
http://forums.parallax.com/forums/default.aspx?f=25&m=185513&g=187262#m187262
I tried rePete's tc.spin and it seems to work ok. Though in the end for our project we decided not to use the DS2760 as the one wire code used up to many cogs. So we ended up using an "Analog devices AD595 thermocouple amp"(link below) which we then just connected to our MCP3208 ADC.
http://www.analog.com/en/prod/0,2877,AD595,00.html
Any ways hope this helps! If you have any more questions just ask, I have quite a bit of experience with thermocouples and other temperature sensors.
Jordan