# Hall sensor mount for TO-92S (A3144 / SS49E)

> How do I mount a hall sensor to measure RPM?

- Category: Stirling engines › Generators & instruments
- Kind: Hardware
- Basis: Block sized to the A3144 UA / SS49E TO-92S body (4.09 × 1.52 mm), M3 foot hole at ISO 273 clearance (Ø3.4)
- Page: https://xemstudio.com/objects/hall-sensor-mount/ · JSON: https://xemstudio.com/api/geometry?object=hall-sensor-mount · Plain text: https://xemstudio.com/objects/hall-sensor-mount/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

**Exact dimensions.** Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part.

## Notes

- The mount is a 14 × 10 × 20 mm block with a 4.09 × 1.52 × 10 mm deep slot in the top face for a TO-92S (UA) hall sensor body, exact.
- The slot sits 1.24 mm behind one 14 mm face, so the sensor's face is that close to the passing magnet side.
- A Ø3.4 hole (M3 clearance) runs through the 10 mm thickness, 5 mm above the base, for the screw that holds it.
- One magnet passing gives one pulse: rpm = pulses per second × 60 / magnets per revolution; on the 12-pole axial-flux rotor that is pulses × 60 / 12.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| sensor slot | 4.09 × 1.52 | A3144 UA / SS49E TO-92S body | press | hall-sensor-mount-* |
| foot hole | Ø3.4 | M3 screw clearance | designed | hall-sensor-mount-* |

## Sizes

| feature | size_mm |
|---|---|
| block | 14 × 10 × 20 |
| sensor slot | 4.09 × 1.52 × 10 deep |
| slot to face | 1.24 |
| foot hole | Ø3.4 (M3) |

## Where the files are

- Wikipedia: [Thermocouple](https://en.wikipedia.org/wiki/Thermocouple) — web — CC BY-SA 4.0 (text)
- Wikipedia: [Hall effect sensor](https://en.wikipedia.org/wiki/Hall_effect_sensor) — web — CC BY-SA 4.0 (text)
- Wikipedia: [Dial indicator](https://en.wikipedia.org/wiki/Dial_indicator) — web — CC BY-SA 4.0 (text)
- Analog Devices: [DS18B20 datasheet](https://www.analog.com/en/products/ds18b20.html) — PDF — Manufacturer datasheet
- Long Earth Society: [Engine and rig builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/hall-sensor-mount/index.json

- hall-sensor-mount-to92: [STEP](https://xemstudio.com/files/hardware/instrument-mounts/hall-sensor-mount-to92.step) · [STL](https://xemstudio.com/files/hardware/instrument-mounts/hall-sensor-mount-to92.stl) — hall sensor mount (A3144 UA / SS49E TO-92S): 4.09 × 1.52 body slot, Ø3.4 (M3 clearance) foot hole

## How it fits

### Goes in or on
- [Axial-flux rotor plates: Ø90 with 12 magnets (Ø8 bore), Ø70 with 8 magnets (Ø5 bore)](https://xemstudio.com/objects/axial-flux-rotor/): faces a rotor magnet: 12 pulses per revolution

### Connects to
- [Neodymium disc magnets, common sizes](https://xemstudio.com/objects/neodymium-disc-magnets/): sensor face 1–2 mm from a passing magnet

### Alternatives
- [Optical encoder disc Ø60, 30 slots, Ø5 bore](https://xemstudio.com/objects/encoder-disc/): optical pickup through an IR slot sensor

## Questions

**What size is a TO-92S hall sensor body?**

4.09 × 1.52 mm (A3144 UA package, SS49E); the slot is drawn at exactly that.

**How do I measure Stirling engine RPM with a hall sensor?**

Put the sensor 1–2 mm from a magnet on the flywheel or rotor; rpm = pulses per second × 60 / magnets per revolution.

## Fits with

- [Axial-flux rotor plates: Ø90 with 12 magnets (Ø8 bore), Ø70 with 8 magnets (Ø5 bore)](https://xemstudio.com/objects/axial-flux-rotor/)
- [Optical encoder disc Ø60, 30 slots, Ø5 bore](https://xemstudio.com/objects/encoder-disc/)
- [Neodymium disc magnets, common sizes](https://xemstudio.com/objects/neodymium-disc-magnets/)
- [Split probe clamps for Ø3, Ø4.8, Ø6 probes and Ø8 / Ø9.53 dial-indicator stems](https://xemstudio.com/objects/probe-clamps/)
- [Crank discs for a Ø5 shaft, 10 to 30 mm stroke](https://xemstudio.com/objects/crank-discs-5mm-bore/)