Abstract

The calibration points for sensors must be selected carefully. This study uses accuracy and precision as the criteria to evaluate the required numbers of calibration points required. Two types of electric relative humidity (RH) sensors were used to illustrate the method and the standard RH environments were maintained using different saturated salt solutions. The best calibration equation is determined according to the t-value for the highest-order parameter and using the residual plots. Then, the estimated standard errors for the regression equation are used to determine the accuracy of the sensors. The combined uncertainties from the calibration equations for different calibration points for the different saturated salt solutions were then used to evaluate the precision of the sensors. The accuracy of the calibration equations is 0.8% RH for a resistive humidity sensor using 7 calibration points and 0.7% RH for a capacitance humidity sensor using 5 calibration points. The precision is less than 1.0% RH for a resistive sensor and less than 0.9% RH for a capacitive sensor. The method that this study proposed for the selection of calibration points can be applied to other sensors.

Highlights

  • The performance of sensors is key for modern industries

  • Tests on a single regression coefficient and the residual plots are used to determine the suitability of a calibration equation for relative humidity (RH) sensors that are calibrated using different saturated salt solutions

  • Two types of electric RH sensors were used to illustrate the method for the specification of the optimum number of calibration points

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Summary

Introduction

The performance of sensors is key for modern industries. Accuracy and precision are the most important characteristics. Modern regression has been used as an important role to express the quantitative relationship between independent and response variables for tests on a single regression coefficient [6,7,8,9] This technique used to address calibration equations and the standard deviations of these calibration equations served as the criteria to determine their accuracy [10,11]. Humidity sensors that were calibrated using different saturated salt solutions were tested to illustrate the technique for the specification of optimal measurement points [18,19]. This study determined the effect of the number and type of salt solutions on the calibration equations for two types of humidity sensors. The accuracy and precision were determined in order to verify the method for the choice of the optimal calibration points for sensor calibration

Saturated Salt Solutions
Calibration of Sensors
Establish and Validate the Calibration Equation
Tests on a Single Regression Coefficient
The Estimated Standard Error of Regression
Residual Plots
Measurement Uncertainty for Humidity Sensors
THT-B121
HMP 140A Capacitive Humidity Sensor
HMP 140A CapacitivebHumidity
Evaluation of Accuracy
The Measurement Uncertainty for the Two Humidity Sensors
The of the the Two
Discussion
Conclusions
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