---
title: "Sensing"
url: "https://nearfieldnotes.com/families/sensing/"
site: "Near Field Notes"
---

# Sensing

Notes for when a current or voltage reads wrong.

## Notes

- [Shunt taps](https://nearfieldnotes.com/notes/shunt-taps/): Where do you tap a 0.5 mΩ shunt? At the middle of the pads’ inner edges. With 10 A through the 0.5 mΩ shunt moteus-x1 uses, sense traces there read 10.1 A. Vias 2 mm out on the copper read 14.1 A.
- [Sense position](https://nearfieldnotes.com/notes/sense-position/): Low side, high side or in line: where should a motor drive sense current? Low side, unless the motor needs every volt or a phase shorted to ground must trip the drive. Its amp sits at ground and costs least, but moteus-c1’s amp needs the bottom FET on for 3 µs of each 30 kHz cycle. That caps the motor at 43.7 V of 48 V at best, and moteus-c1’s firmware stops at 39.4 V. In line gives all 48 V and high side catches the short, each with an amp that rides 48 V.

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Source: https://nearfieldnotes.com/families/sensing/