# Remote Low-Cost Differential Isolated Probe for Voltage Measurements
## 1 Introduction  
Measurement with voltage probes for the continuous monitoring and measurement of network nodes is important in today's power system, as it helps to detect potential faults, improving system maintenance and performance. The need for such metering systems will increase day by day, as the current trend is to establish smart grids, where renewable energies are gaining importance. In addition, the emergence of new electrical loads such as electric vehicles and various energy storage devices (batteries with solar panels) is a novelty for electricity distribution systems that can have an impact on the system. To have a smart grid, it is necessary to monitor the grid voltage, and given the changes in the loads of the current electricity system, thecontinuous monitoring of this voltage is necessary. The correct management of these measures requires cyber-physical systems (CPS) made up of computer systems for data processing, communication networks, and sensors that allow interaction with the physical world and the virtual or computer world [1]. This work encompasses two lines of the state of the art: the development of voltage probes with galvanic isolation and the development of Internet of Things (IoT) measurement systems in the field of energy and the measurement of electrical network magnitudes. For this reason, this study is carried out from both aspects. Probes for measuring high voltages can be classified as high-voltage differential probes (non-isolated), and isolated high-voltage probes, which in turn can be analogue or digital probes. Traditionally, high voltages are measured with differential probes without galvanic isolation, such as the probes used for the comparison of the results in this work (Chauvin Arnoux DP25, Barcelona, Spain and a Tektronix P5205, Madrid, Spain). This gives the probes the ability to measure high differential voltages with high bandwidths, between tens and hundreds of megahertz. In the classification of analogue isolated high-voltage probes, two types can be distinguished according to the location of the isolation: those using a non-intrusive sensor/measuring coupling system [1; 2] and those using an intrusive one [3; 4], that connect a circuit to the system and then use a coupling method, either optical, capacitive, inductive, or through the power supply, to achieve the isolation. In [1], the authors present a non-intrusive probe for the non-contact measurement of voltages of 10 kV and a bandwidth of 4.5 MHz, based on the electric field coupling principle using the dual-pin-type probe method. Also based on non-intrusive capacitive coupling, the development of a probe for voltage measurements up to 1000 V, for the direct proportional measurement of the true RMS value containing a 50-60 Hz waveform with a cut-off frequency of 6 kHz, is presented in [2]. These systems [1; 2] are coupling systems designed to clamp the cable to be measured, making them difficult to use when the cables are thin, as the development of mechanical coupling becomes more complex. Other proposals develop solutions based on optical isolation, achieving measurement ranges down to 2 kV with bandwidths from DC to 5 MHz [3], aiming at detecting fast voltage changes. These types of probes require a LED driver and a photodetector as a receiver, which transforms the input voltage into a light signal and the information in the form of lux, back to a voltage value. On the other hand, the high-bandwidth isolated voltage probe presented in [4] is intended for the measurement of source gate voltages of floating transistors in bridge rectifier and inverter configurations. Its input voltage range is \(\pm\)75 V and it has a bandwidth of 130 MHz. Isolation is achieved either by using floating power supplies isolated from each other or through the use of a battery-powered system. The data are acquired with an 8-bit ADC and sent via Bluetooth to a device that displays them graphically. An FPGA interfaces between the ADC and the Bluetooth module.