Hello Adafruit Representative,
I am using the serial thermocouple code (below) offered by Adafruit with sensor MAX31855 and K-type thermocouple.
------------------------------------------------------------------------
This is an example for the Adafruit Thermocouple Sensor w/MAX31855K
Designed specifically to work with the Adafruit Thermocouple Sensor
----> https://www.adafruit.com/products/269
------------------------------------------------------------------------
As I run the code, the output is displayed as:
Internal Temp = 25.56
C = 25.25
Internal Temp = 25.56
C = 25.25
Internal Temp = 25.56
C = 25.25
Internal Temp = 25.56
C = 25.25
Internal Temp = 25.56
C = 25.00
Internal Temp = 25.56
C = 29.50
My question:
1) Why are two temperatures being displayed? Is there an internal temperature sensor located in the board? I am using Leonardo board (ID: 849) and Data Logging Shield (ID: 1141).
Please kindly respond at your convenience.
Warm regards, Savard
internal temp output reading?
Moderators: adafruit_support_bill, adafruit
Please be positive and constructive with your questions and comments.
- adafruit_support_bill
- Posts: 88087
- Joined: Sat Feb 07, 2009 10:11 am
Re: internal temp output reading?
Yes. There is an internal temperature sensor in the thermocouple amplifier. The thermocouple signal is proportional to the temperature differential over the length of the thermocouple. In order to know the temperature at the tip, you need to know the temperature at the other end.
- flosk8
- Posts: 4
- Joined: Sun Sep 28, 2014 12:37 pm
Re: internal temp output reading?
I have currently a temperature of 7.00 for the thermocouple and an inner temperature of 22.00.
So how can I calculate the temperature at the thermocouple tip?
Thanx
So how can I calculate the temperature at the thermocouple tip?
Thanx
- adafruit_support_bill
- Posts: 88087
- Joined: Sat Feb 07, 2009 10:11 am
Re: internal temp output reading?
If the MAX31855 says 7.00, then that is the tip temperature. The MAX31855 chip takes the internal temperature into account to generate that number.
- flosk8
- Posts: 4
- Joined: Sun Sep 28, 2014 12:37 pm
Re: internal temp output reading?
How can that be? I have a temperature of around 22 C. And the thermocouple tells me it's 7.
- adafruit_support_bill
- Posts: 88087
- Joined: Sat Feb 07, 2009 10:11 am
Re: internal temp output reading?
Are you using a K-type thermocouple?
If you hold the tip of the thermocouple between your fingers, does the temperature increase?
Post photos showing your soldering and connections to the board.
If you hold the tip of the thermocouple between your fingers, does the temperature increase?
Post photos showing your soldering and connections to the board.
- flosk8
- Posts: 4
- Joined: Sun Sep 28, 2014 12:37 pm
Re: internal temp output reading?
Mhhhh it seems not to be the soldering.
I have a two channel MAX31855 with two thermocoules one is showing the right temperature of about 20 and the other one only 7. It has to be the thermocouple and not the MAX31855 . Because when I change the ports its still the one that shows only 7.
I wonder whats going on here because they are both K Type with green and white pins.
Any Idea?
I have a two channel MAX31855 with two thermocoules one is showing the right temperature of about 20 and the other one only 7. It has to be the thermocouple and not the MAX31855 . Because when I change the ports its still the one that shows only 7.
I wonder whats going on here because they are both K Type with green and white pins.
Any Idea?
- adafruit_support_bill
- Posts: 88087
- Joined: Sat Feb 07, 2009 10:11 am
Re: internal temp output reading?
It could just be a mismarked probe. The color code for K-type in this country is -red/+yellow. But we have seen some samples where the colors are reversed.
- flosk8
- Posts: 4
- Joined: Sun Sep 28, 2014 12:37 pm
Re: internal temp output reading?
Nope I definetly poled them right. Green=+ White=-
Because its increasing temperature when i hold it in my hand.
But still its about 13 degrees to less.
Can it be that a thermocouple is buggy? This one has a two meter cable, can that be the problem? The 2 port MAX31855 is for 3,3V.
I also have the problem that even if the temperature remains the same I get changes up to +/- one degree when I read every second. What could that be?
Because its increasing temperature when i hold it in my hand.
But still its about 13 degrees to less.
Can it be that a thermocouple is buggy? This one has a two meter cable, can that be the problem? The 2 port MAX31855 is for 3,3V.
I also have the problem that even if the temperature remains the same I get changes up to +/- one degree when I read every second. What could that be?
- adafruit_support_bill
- Posts: 88087
- Joined: Sat Feb 07, 2009 10:11 am
Re: internal temp output reading?
Probably either a mis-marked (i.e. not a K-type) or improperly constructed thermocouple.
If it is not a K-type extension cable, that can definitely be a problem.This one has a two meter cable, can that be the problem?
That shouldn't make any difference. The thermocouple voltages are in the microvolt range.The 2 port MAX31855 is for 3,3V.
That could be just noise. Since the amplifiers need to be very sensitive to work with microvolt-level signals, they are also prone to picking up noise. It is common to take the average of several readings to minimize the noise.I also have the problem that even if the temperature remains the same I get changes up to +/- one degree when I read every second. What could that be?
Please be positive and constructive with your questions and comments.