GTC 1.5.1

The GUM Tree Calculator for Python

The GUM Tree Calculator is a Python package for processing data with measurement uncertainty.

Python objects, called uncertain numbers, are used to encapsulate information about measured quantities. Calculations of derived quantities that involve uncertain numbers will propagate this information automatically. So, data processing results are always accompanied by uncertainties.

GTC follows international guidelines on the evaluation of measurement data and measurement uncertainty (the so-called GUM). It has been developed for use in the context of metrology, test and calibration work.

Example: an electrical circuit

Suppose the DC electrical current flowing in a circuit and the voltage across a circuit element have both been measured.

The values obtained were 0.1 V, for the voltage, and 15 mA for the current. These values have the associated standard uncertainties 0.001 V and 0.5 mA, respectively.

Uncertain numbers for voltage and current can be defined using the function ureal()

>>> V = ureal(0.1,1E-3)
>>> I = ureal(15E-3,0.5E-3)

The resistance of the circuit element can then be calculated directly using Ohm’s law

>>> R = V/I
>>> print(R)
6.67(23)

The uncertain number R represents the resistance of the circuit element. The value 6.67 ohm is an estimate (or approximation) of the actual resistance. The standard uncertainty associated with this value, is 0.23 ohm.

Installation

GTC is available as a PyPI package. It can be installed using pip

pip install gtc

Dependencies

• Python 2.7, 3.5+

• scipy

Documentation

The documentation for GTC can be found here.