## 3 Development of Thermal Condition Monitoring System
### ZigBee and Wireless Sensor Networks Characteristics  
Progression in the development of the WSNs monitoring system to improve the performance of thermal conditions reduce the cost of thermal conditions monitoring scheme compared to the traditional wired-sensor network [21; 63]. The ZigBee WSNs technology standards are of low-cost and self-coordinating [56]. It has excellent performance and seeks to overcome the economic aspect of industrial communication concerning capital and operational expenditures. The ZigBee WSNs sensor nodes can easily be added or removed from the local WSNs and the installation and maintenance costs are meagre. Additionally, it can be designed and configured at ease to operate directly from any terminal point with no restrictions or constraints for cable's region. ZigBee WSNs has reliable security configuration; different levels of data access can be assured and may not be compromised [56]. It allows possible local and remote signal feedbacks to be managed, employing suitable security actuation and data measurement transfers. The components of the ZigBee WSNs consist of three essential elements, namely the sensor nodes, radio communication with the router through star architecture or connected in a gateway mesh network that acts as an interface between WSNs, and the application platform [21; 61; 77; 81; 82]. In the industrial application, WSNs gateway acts as the data sink for the sensor nodes and connect to the application platform through connections of LAN or GSM.  
Ideally, the technology works globally on 2.4 GHz as unlicensed spread spectrum ISM band, however there are other ISM bands which ZigBee is compatible with [58; 60; 61]. ZigBee data rate characteristics range between 10 kbit/s and 250 kbit/s on the 2.4 GHz band with a line of sight from 80 m to 1.5 km depending on the application configuration. The usual standard transmission line of sight range for most home applications has been about 100 m [58; 60]. Additionally, advancement in the ZigBee technology proposes various schemes to improve data rate and signal sensitivity with an increase in the line of sight ranges [52; 58; 60; 83; 84]. ZigBee has additional functioning characteristics regarding security, which determines the ability of the communication link to transmit or receive a signal with improved reliability against any form of interference. The ZigBee WSNs guarantee sensors node switching of wireless communication capabilities, which are compliant with ZigBee IEEE standard 802.15.4 and involves more sensors integration in the network where applicable. Sensors node do not communicate with each other directly, but through the network routers or the configuration of the on-board mesh switching, constituting the self-organized WSNs. Routers are always designed to be on and should always have active power sources [21; 54; 55; 56; 77]. Table 2, presents the features of ZigBee device being used in this paper.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**ZigBee Technology (XBee-Pro ZigBee (S2C))** \\ \hline
**Overview:** Higher Signal Strength, Less Power Consumption and Longer Range. \\ \hline \hline \multicolumn{2}{c}{**Characteristics**} \\ \hline Frequency & 2.4 GHz \\ Data rate & RF-250 kbps: Serial:1 Mbps \\ Maximum power transmit & 63 mW (18 dBm) \\ Max. current consumption (Transmitting) & 120 mA \\ Maximum receiver sensitivity & \(-\)101 dBm \\ Max. current consumption (Receiving) & 45 mA \\ Max. current consumption (sleep) & \(<\)1 uA \\ Maximum line of sight range & 3.2 km \\ Supply voltage & 2.7–3.6 VDC \\ Operating temperature & \(-\)40\(-\)\(+\)85 \({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table}
Table 2: ZigBee Technology Characteristics.