Thermocouple emf reference functions
Project description
Python module containing calibration data and lookup functions for standard thermocouples of types B, C, D, E, G, J, K, M, N, P, R, S, T, and some less standard types too.
Usage and examples
Below, the first computation shows that the type K thermocouple emf at 42 °C, with reference junction at 0 °C, is 1.694 mV (compare to NIST table); the second calculation shows how passing in an array applies the function for each element, in the style of numpy:
>>> from thermocouples_reference import thermocouples >>> typeK = thermocouples['K'] >>> typeK <Type K thermocouple reference (270.0 to 1372.0 degC)> >>> typeK.emf_mVC(42, Tref=0) 1.6938477049901346 >>> typeK.emf_mVC([3.14159, 42, 54], Tref=0) array([0.12369326, 1.6938477 , 2.18822176])
An inverse lookup function is provided that you can use to get a temperature out of a measured voltage, including cold junction compensation effects. If we put our type K thermocouple into a piece of spam and we read 1.1 mV, using our voltmeter at room temperature (23 °C), then the spam is at 50 °C. [1]
>>> typeK.inverse_CmV(1.1, Tref=23.0) 49.907928030075773 >>> typeK.emf_mVC(49.907928030075773, Tref=23.0) # check result 1.1000000000000001
The functions are called emf_mVC and inverse_CmV just to remind you about the units of voltage and temperature. Other temperature units are supported as well:
Temperature unit 
EMF lookup 
Inverse lookup 

degrees Celsius 
.emf_mVC 
.inverse_CmV 
degrees Fahrenheit 
.emf_mVF 
.inverse_FmV 
kelvins 
.emf_mVK 
.inverse_KmV 
degrees Rankine 
.emf_mVR 
.inverse_RmV 
You can also compute derivatives of the emf function. These are functional derivatives, not finite differences. The Seebeck coefficients of chromel and alumel differ by 42.00 μV/°C, at 687 °C:
>>> typeK.emf_mVC(687,derivative=1) 0.041998175982382979
Data sources
Readers may be familiar with thermocouple lookup tables (example table). Such tables are computed from standard reference functions, generally piecewise polynomials. [2] This module contains the source polynomials directly, and so in principle it is more accurate than any lookup table. Lookup tables also often also include approximate polynomials for temperature lookup based on a given compensated emf value. Such inverse polynomials are not included in this module; rather, the inverse lookup is based on numerically searching for a solution on the exact emf function.
For any thermocouple object, information about calibration and source is available in the repr() of the .func attribute:
>>> typeK.func <piecewise polynomial+gaussian, domain 270.0 to 1372.0 in degC, output in mV; ITS90 calibrated, from NIST SRD 60, type K>
The data sources are:
Types B, E, J, K, N, R, S, T use coefficients from NIST’s website, and are calibrations to the ITS90 scale. [3]
Types G, M, P, and nonlettered types Au/Pt, Au/Pd, AuFe 0.07, IrRh 40/0, PtMo 5/0.1, PtRh 40/20 use coefficients from ASTM E 175100 and are calibrations to ITS90.
Types C, D [4] use coefficients found from a publication of OMEGA Engineering Inc., and are calibrations to IPTS68 scale. [5]
Graphs of functions (if you don’t see anything, see low temperature types here, intermediate temperature types here, and high temperature types here):
Requirements
numpy
scipy (optional, only needed for inverse lookup)
python2 or python3 languages
Installation
Recommended installation is via pip. First, install pip. Then:
pip install thermocouples_reference user
(Remove the user option if you are superuser and want to install systemwide.)
Disclaimer
This module is provided for educational purposes. For any realworld process, I strongly recommend that you check the output of this module against a known good standard.
I make no warranties as to the accuracy of this module, and shall not be liable for any damage that may result from errors or omissions.
Project details
Release history Release notifications  RSS feed
Download files
Download the file for your platform. If you're not sure which to choose, learn more about installing packages.
Source Distribution
Hashes for thermocouples_reference0.20.tar.gz
Algorithm  Hash digest  

SHA256  94dd18ce6d44e92fffafbb0caf4ed2452efbc31a763850ff439929717f0f4f84 

MD5  9c2dbe3ba24834811a936d451f254a7a 

BLAKE2b256  f9384baa55697a347878f540ac1189e70ae40f8878dc400d526232c6ab779d6a 