# A Cyber-Physical Approach for Residential Energy Management: Current State and Future Directions
## 4 Data Acquisition
### Metering Devices
Smart plugs were also highlighted in [97] as one of the leading technologies for data acquisition. The appearance of a smart plug is an important aspect regarding the acceptability by users. It must be small, compact, and compatible with traditional plugs. Besides this, it should not add more complexity when it comes to installation and use. The design of commercially available smart plugs is possible when it largely satisfies the question of aesthetic appeal and form factor. Therefore, an ideal smart plug will be a smart combination of various technologies that have been routinely used independently until now [96]. With respect to healthcare applications, a recent approach in [17] aimed to design and develop an IoT end-to-end solution based on CT sensors to recognize electric appliances that could operate in real-time, considering low-cost hardware. Other approaches such as [98; 99] presented a solution based on wearable sensors, such as accelerometers and smart devices, and in the case of [100], the authors used a camera to record the video and a processor that performed the task of recognition. A different solution is illustrated in [101], in which the authors designed a distributed platform to monitor patient's movements and the status during rehabilitation exercises. This information could be processed and analyzed remotely by the doctor appointed to the patient. To summarize the above discussion, Table 3 lists devices commonly used for Data Acquisition in HEMS. The \"Type\" and \"Category\" columns refer to the nature of the device. If the device is classified as a sensor, then it changes a physical parameter to an electrical output. Otherwise, the actuator is a device that converts an electrical signal to a physical output [102]. The category describes the kind of measurement that can be expected using such devices. It could be either ambient (temperature, humidity, occupation, etc.) or electrical (to obtain power measurements). In addition, the last column of Table 3 shows some of the main manufacturers and sellers in the market up to date. This list is independent from the \"References\", meaning that the authors of previous papers could have used one device from these sellers or not. \begin{table}
\begin{tabular}{c c c c} \hline
**Device** & **Type** & **Category** & **References** & **Manufactures** \\ \hline Temperature sensor & Sensor & Ambient & [76; 78; 103; 104; 105] & NCD, Ecobee, Sensibo, Google Nest \\ Humidity sensor & Sensor & Ambient & [76; 95; 103; 106] & NCD, Aeotec, Aqara, Govee \\ Air quality sensor & Sensor & Ambient & [76; 107] & Airthings, Eve, Awair, Bosch \\ Water sensor & Sensor & Ambient & [76; 108], Dataport & Govee, Zircon, Fibaron, Moen \\ Occupancy sensor & Sensor & Ambient & [76; 104] & Ecolink, Zooz, Fibaron, Apple, \\ Door sensor & Sensor & Ambient & [76; 80; 109] & Eve, Wyze, Geeni, Samsung \\ Current transformer (CT) & Sensor & Electrical & [17; 19; 43; 52; 110; 111] & IoTaWatt, EmonLib, Schneider Electric, CrocSee \\ Smart Socket & Actuator & Electrical & [43; 46; 76; 112; 113; 114; 115] & YinQin, WeMo, TP-Link, Gosund \\ \hline \end{tabular}
\end{table} 
Table 3: Commonly used consumer-side metering devices for data acquisition in HEMS.