Question

The calibration of a pressure sensor with a range of 0-16 bar is checked by applying known inputs to it in steps of 2 bar. The following measurements were obtained.

Known input pressure (bar)	0	2	4	6	8	10	12	14	16
Output reading (V)	0.00	0.55	1.25	1.70	2.35	3.15	3.65	4.05	4.85

1. Draw a graph by plotting the data points on a graph paper and draw a best-fit straight line through the data points.                                                       [8 marks]

2. Use the above graph to calculate:

1. The measurement sensitivity of the pressure sensor.                  [2 marks]

2. The maximum non-linearity apparent in the measurements as a percentage of the full-scale deflection.                                       [6 marks]

Answer 1

MATLAB CODE:

x = 0:2:16; % known input pressures
y = [0.00 0.55 1.25 1.70 2.35 3.15 3.65 4.05 4.85]; % output values
plot(x,y,'bo','MarkerSize',6);
[p,S] = polyfit(x,y,1); % best fit line
[y_fit,delta] = polyval(p,x,S); % error estimates
hold on
plot(x,y_fit,'r-');
grid;
legend('Actual data','Line of best fit');
clc;
fprintf('The sensitivity is %f ',p(1));
fprintf('The maximum error is %f percent ',delta(1)*100/4.85);

OUTPUT:

The sensitivity is 0.301250 The maximum error is 2.365051 percent