A Calibration Report for Wireless Sensor-Based Weatherboards

Muthoni Masinde,Antoine Bagula

doi:10.3390/jsan4010030

Abstract

Sub-Saharan Africa contains the highest number of people affected by droughts. Although this can easily be mitigated through the provision of timely, reliable and relevant weather forecasts, the sparse network of weather stations in most of these countries makes this difficult. Rapid development in wireless sensor networks has resulted in weatherboards capable of capturing weather parameters at the micro-level. Although these weatherboards offer a viable solution to Africa’s drought, the acceptability of such data by meteorologists is only possible if these sensors are calibrated and their field readiness scientifically evaluated. This is the contribution of this paper; we present results of a calibration exercise that was carried out to: (1) measure and correct lag, random and systematic errors; (2) determine if Perspex was an ideal material for building sensor boards’ enclosures; and (3) identify sensor boards’ battery charging and depletion rates. The result is a calibration report detailing actual error and uncertainty values for atmospheric pressure, humidity and temperature sensors, as well as the recharge and discharge curves of the batteries. The results further ruled out the use of Perspex for enclosing the sensor boards. These experiments pave the way for the design and implementation of a sensor-based weather monitoring system (SenseWeather) that was piloted in two regions in Kenya.

Highlights

According to the World Disasters Report of 2013, Africa contained 56% of the droughts that occurred between 2003 and 2012; they affected 26% of her population
What change or bias will there be in the data if it replaces a different sensor measuring the same weather element(s)?. This was achieved by assessing the following factors: (1) The sensors boards’ lag errors; these result from: delay statements used for stabilizing power supply after waking up the sensor boards; the process of storing the readings in secure digital (SD) cards; print and println statements; and general packet radio service (GPRS) commands; (2) The effects of enclosing the sensor boards in a Perspex enclosure; (3) The sensors boards’ battery discharge and recharge curves; this would enable one to know the frequency with which the deployed sensors’ batteries needed to be recharged/replaced
The weather instruments operated at the Observatory Unit of the Kenya Meteorological Department (KMD) were used for the calibration experiments described in this paper

Summary

Introduction

According to the World Disasters Report of 2013, Africa contained 56% of the droughts that occurred between 2003 and 2012; they affected 26% of her population. The uniqueness of the problem in SSA is the inadequacy and ineffectiveness of the region’s preparedness for these disasters [2,3] This is partly attributed to the fact that the meteorological institutions (the National Meteorological Services (NMSs)) charged with weather forecasting rely on weather stations that are thousands of kilometers apart [4,5]. The weather instruments operated at the Observatory Unit of the Kenya Meteorological Department (KMD) were used for the calibration experiments described in this paper. KMD is both a national (Kenya) and regional (the Horn of Africa) center for drought forecasting and other related activities, and as such, the Department is equipped with an array of weather monitoring equipment. The Unit has an automatic weather station (AWS) from which weather parameters are automatically relayed to their computer systems

Objectives

Results

Conclusion