# Can I use my doorbell transformer to measure voltage for real power measurement? **URL:** \ **Category:** Hardware\ **Created:** [14 January 2024 23:41 UTC](https://community.openenergymonitor.org/t/can-i-use-my-doorbell-transformer-to-measure-voltage-for-real-power-measurement/25336 "2024-01-14T23:41:43Z")\ **Posts on this page:** 1\ **Showing post:** 63
**Author:** ![Robert.Wall](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/robert.wall/32/38246_2.png) [@Robert.Wall](https://community.openenergymonitor.org/u/Robert.Wall)\ **Post date:** [3 February 2024 19:11 UTC](https://community.openenergymonitor.org/t/can-i-use-my-doorbell-transformer-to-measure-voltage-for-real-power-measurement/25336/63 "2024-02-03T19:11:22Z")
As far as I can recall, I’ve never seen anything to measure THD here **using** OEM kit. And the reason is that generally, we can’t sample fast enough or store enough data (until we started using the -DB series processor). I’ve used either a Windoze PC Oscilloscope and laptop sound card or, since I got a real DSO, this to sample the waveforms and then move the data into a spreadsheet. There’s a link to it somewhere 🤔 [ZMPT101B, powerfactor and current shown - #52 by Robert.Wall](https://community.openenergymonitor.org/t/zmpt101b-powerfactor-and-current-shown/11939/52) but this only does the harmonics individually - though it’s trivial to sum them. This is how I measure transformer phase error. I haven’t got a feel for what the ESP32 can do, so I can’t offer a suggestion as to whether it’s doable or not. --- _[View the full topic](https://community.openenergymonitor.org/t/can-i-use-my-doorbell-transformer-to-measure-voltage-for-real-power-measurement/25336)._