Voltage divider with calibration V2 - for measuring Geiger counter high voltage

I recently got a new multimeter that has a slightly higher burden than the meter I was previously using. This meant that the original voltage divider I made wouldn't calibrate to my new meter. The solution was to increase the resistance of R2 in the divider.

On the v1 divider R2 was made up of a 1MΩ and a 100KΩ trimmer pot in series. To increase the R2 in the v2 divider I added a couple of 100KΩ resistors in series with the 100KΩ trimmer pot. R2 became 1MΩ + 100KΩ + 100KΩ + 100KΩ (pot) all in series. I added two jumpers alongside the two new 100KΩ resistors so I can put them in circuit or remove them from circuit to suit a wide range of multimeters. I figure I should be able to use a meter with an internal resistance as low as 5, or 6MΩ.

I have had it on the cards for some time to make a new voltage divider that was multifunctional and could cover various ranges, so I took this opportunity to do so. Instead of just having one R1 (1GΩ in the v1) I decided to include three R1's. A 10MΩ, 100MΩ and 1GΩ. I added a small header and I can select any one of the three resistors by moving a jumper. This enables me to use this as a 10:1, 100:1 and 1000:1.

The resistors I used are rated for in excess of 7000V, however due to the construction and placement of components and the board used, the chances for creepage are high at high voltages. I wouldn't normally use this past 1000V, though I may push it on occasion. It's not a product, just a homebrew tool that makes certain jobs much easier, and accurate.

The construction is about as simple as the pictures show. I did run solid core wire for all traces on the PCB bottom and soldered to every via on their way. It helps a little to keep resistances as low as possible, but probably not needed with this. When handling the unit, plugging in, unplugging etc, I kept bending the long thin resistors in towards the middle of the board. I added some hot glue to keep them tight in place. Nothing to do with insulation or anything, just to support the resistors.

I write this about a month after knocking this up and I have used it a lot. It works very well and I can calibrate to every meter I have used it with so far, even an old AVO 8 MK5. There is one thing I have not done with this so far, and that is use the 10:1 or 100:1 ranges. I seem to find the 1000:1 range just fits for everything so far, so did I need to include the lower two ranges? Time will tell, but so far, no need for them. I have a Swiss army knife of voltage dividers, yet just use the same blade over and over.

And of course, now I have two 1000:1 voltage dividers. The v1 I leave set to my old Siemens meter, and the v2 I have calibrated to me new meter. I shouldn't struggle measuring high(ish) voltages in the future! 😊