High Voltage Probe with Voltage Devider

thingiverse

Starting with warnings: Dealing with high voltages is perilous. Therefore, use this design at your own risk only. Only utilize this design if you are qualified to assess risks by your professional expertise. This design is not suitable for high-voltage power grid applications because it is too short to provide sufficient safety distance. It is only suitable for high-impedance sources. Since I found no information about the isolation properties of PLA, I assume PLA is not suitable for insulation purposes. Consequently, it is not suitable for this project. Besides, the design provides a high creepage distance on its surface; however, FDM prints tend to have fine fissures that might compromise the insulation. Especially if the part is contaminated with conductive dirt. Resistors have distinct voltage ratings. The voltages they can withstand are limited by more than just power dissipation. They are commonly rated between 300 and 500V. That's why I'm using 30 resistors in series to achieve 10000V There may be additional considerations to take into account. Let us continue with known limitations. Limitations: As explained above, the practical usage is limited to 10000V non-power grid applications. The extremely high (100MOhm) input resistance makes it very susceptible to EMI (electromagnetic interference). The helical shape of the tunnel for the resistors may exacerbate this problem. Measuring DC is relatively reliable; however, AC is a significant concern. Grounding the probe helps somewhat. Usage: Inside the shaft is an helical tunnel to accommodate a long series of resistors. The simplest usage is to install a 90MOhm series resistor in conjunction with the 10MOhm (commonly) internal Resistor of voltmeter. This divides the readings by ten. An additional parallel Resistor can be installed to set other dividing factors. To minimize the influence of EMI, the configuration as voltage divider is preferable; however, you can leave the ground terminal floating to revert back to using it as a simple pre-resistor. To minimize EMI, route the ground wire from the subject to the ground terminal of the probe first and then to the common terminal of your voltmeter. Assembly: For installing the resistors inside the body of the shaft, feed a folded nylon string through the helical cavity. If this doesn't work, use a vacuum to suck a thread through. Solder the resistors in series and pull the string of resistors through by gently pushing from the other side. I found this surprisingly easy. Use shrinking tube to isolate the remaining resistors. Solder the first resistor to the tip. The tip can be made from 2mm diameter round stock. I used brass because it is easy to solder and not too sensitive to corrosion. Complete the internal wiring as shown in the pictures. Use wires with dielectric strength of at least 1000V. The ones I used are too skinny. The plugs I used are certified for 1000V. To improve isolation, fill the thread between the shaft and the handle with epoxy. Be extremely cautious when dealing with high voltages!