en:calibration

# Differences

This shows you the differences between two versions of the page.

 — en:calibration [2018/01/29 10:12] (current) 2014/04/18 18:41 admin created 2014/04/18 18:41 admin created Line 1: Line 1: + ===== Calibration ===== + ==== Two point calibration ==== + For this way of calibration there must be a linear response of measuring tool on change of meassured variable and two samples with known value of measured variable (eg. ion concentration). + + Thats all we need. Because linear characteristic is a line in two dimensional space (plane). And the line in 2-D space can be described definitely by two points (calibration samples). And position of point in 2-D is defined by two coordinates. The first coordinate is a response of measuring tool and the second one is value of measured variable. ​ + + Measuring tool need to know the equation of this line for correct meassuring. It is: + + **y=ax+b** + + In this case **y** is the value of measured variable and **x** is meassuring tool response **a** and **b** are constants which we need to assign. + We have got this two equations for two unknown:​\\ ​ + - **y<​sub>​1​=ax<​sub>​1​+b**\\ + - **y<​sub>​2​=ax<​sub>​2​+b**\\ + Now it's up to our decision, how do we solve the equation. + + Example:\\ + We want to calibrate our EC metr. + At first we need two samples with known conductivity (eg. EC(1)=2, EC(2)=6)\\ + From equations 1 and 2 we express **a** by subtracting them\\ + **a=(y<​sub>​1​-y<​sub>​2​)/​(x<​sub>​1​-x<​sub>​2​)**\\ + y<​sub>​1,​y<​sub>​2​ are concentrations of our samples(2,​6)\\ + Now we need to know the response of meassurig tool to our samples. We get 65 for EC=2 and 256 for EC=6\\ + We substitute into our equations:​\\ + a=(6-2)/​(256-65)≅0,​0209\\ + and we get **a**, which is slope of the line. Sustituting **a** into one of equations we get exact position of the line. \\ + b=y-a*x=6-256*0,​0209=0,​6496\\ + So the equation for our meassuring tool is:\\ + EC=0,​0209*meassuring tool response+0,​6496\\ + {{wiki:​kalibrace.png}} +
en/calibration.txt · Last modified: 2018/01/29 10:12 (external edit)

### Page Tools 