# Remote Low-Cost Differential Isolated Probe for Voltage Measurements
## 5 Conclusions  
An IoE isolated voltage probe for the remote monitoring of mains voltage quality according to EN 50160 has been successfully designed, implemented, and validated by performing a complete set of performance tests. The performance of the hardware part has been tested under different operating conditions (Section 3.1), comparing the results with different commercial probes under the same operating conditions, such as Chauvin Arnoux DP25 and Tektronix P5205. The results obtained show that for voltage measurements up to 600 V within the necessary bandwidth for the verification of the European standard EN 50160, the proposed design meets the established requirements. Being isolated and differential, the proposed probe provides protection to the digitising and communications system, unlike the high-voltage differential probes Chauvin Arnoux DP25 and Tektronix P5205 which lack isolation.  
Once the isolation and conditioning circuit was validated, the probe was provided with an acquisition and communication system providing it with features for its application in the Internet of Energy. For the validation, a Wi-Fi-based IoE network was deployed with a MQTT protocol with single-point and multipoint measurements, allowing to verify the performance in both situations. The results are presented in Section 3.2.  
After performing the measurements and the transmission through the communication protocol, the harmonic analysis of the acquired signals was carried out, comparing the remote measurements with the maximum theoretical harmonic values established in the European standard EN 50160, for which the FFT of both signals was performed. This shows that the developed probes allow the detection and localisation of disturbances at different points in a line or generation system.  
A low-cost isolated probe was developed with analogue galvanic isolation of the capacitive type, which is suitable for use in IoT and IoE applications without the need for device supervision and allows continuous and remote monitoring as it has connectivity through the MQTT protocol. It should be noted that the MQTT protocol is free to use and there are open-source implementations that do not increase the cost of the system; what really jeopardizes the cost is the hardware needed to operate with it. In this sense, the selection of all probe components was carefully carried out, taking into account the low-cost requirement, both in the instrumentation part with the IA with galvanic isolation, and in the communication devices, the Arduino Nano used for the publisher, as well as the Raspberry Pi used for the broker. The Pubsub library used on the Arduino is published under an MIT license, while the Paho library used on the PC and the Mosquito broker software are licensed under Eclipse Public License 1.0 and Eclipse Distribution License 1.0 (BSD), and are free to use.  
Project conceptualization, D.A.-C., F.J.P.-C., D.E., B.C. and N.M.; software development, D.A.-C. and D.E.; design test and validation D.A.-C. and F.J.P.-C.; paper writing. D.A.-C.; paper reviewing F.J.P.-C., D.E., B.C. and N.M.; funding acquisition, B.C. and N.M. All authors have read and agreed to the published version of the manuscript.  
This work has been supported through grants PID2019-106570 RB-I00 (AEI/10.13039/501100 011033), PID2022-138785 OB-I00 (MCIN/ AEI/10.13039/501100011033/FEDER, UE), and the Government of Aragon PhD grant BOA20201210014.  
**Institutional Review Board Statement:** Not applicable.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Authors** & **Microcontroller** & **RF Technology** & **Gateway** \\ \hline
[28] & Arduino Pro Micro & IEEE 802.15.4 & Custom XBee Pro + WIZnet POE Ethernet \\ \hline
[29] & Arduino Uno & – & – \\ \hline
[30] & Arduino MKR WAN & LoRa & LoRa Gateway \\ \hline This work & Arduino Nano 33 IoT & Wi-Fi & Raspberry Pi \\ \hline \end{tabular}
\end{table}
Table 4: Proposed probe elements vs. other proposed IoT energy monitoring systems.