# Instrumentation: DS18B20 and K-type probes, hall sensor, encoder disc, dial-indicator stems

> What are DS18B20 waterproof probe and K-type thermocouple probe dimensions?

- Category: Stirling engines › Generators & instruments
- Kind: Hardware
- Basis: Common probe sizes: DS18B20 stainless sleeve Ø6 × 50 (some Ø6 × 30), K-type sheathed probes Ø3 / Ø4.8 (3/16 in), bead thermocouples 0.3–1 mm wire; dial indicators Ø8 mm (metric) / Ø9.53 (3/8 in) stems; TO-92 hall sensors
- Page: https://xemstudio.com/objects/instrument-mounts/ · JSON: https://xemstudio.com/api/geometry?object=instrument-mounts · Plain text: https://xemstudio.com/objects/instrument-mounts/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

## Notes

- DS18B20 waterproof: Ø6 × 50 mm stainless sleeve, 1 m cable, −55 to 125 °C (so the cold side only). K-type: bare bead (0.3–1 mm wire) to 1000 °C for the hot end; sheathed Ø3 × 100 or Ø4.8 × 100 with a mini-K plug; MAX6675/MAX31855 boards read them. Mount probes in a split clamp (Ø + 0.15, M3 pinch) and leave 10 mm of sheath in the gas path.
- RPM: TO-92 hall sensor (A3144 digital, SS49E analogue) in the printed mount 1–2 mm from a passing magnet; or the Ø60 slotted encoder disc through an IR slot sensor (TCST2103, 3 mm gap): 30 slots → 30 pulses/rev.
- Dial indicator stems: Ø8 mm (metric) or Ø9.53 (3/8 in, US); the clamps here hold them for measuring displacer travel and flywheel runout. Stroke of a Stirling displacer: measure at the rod with the engine turned by hand.
- LES: hot-end K-type under the ferrule clamp, DS18B20 on the cold spool, hall sensor at the flywheel rim, dial indicator on the displacer rod during commissioning.

## Sizes

| sensor | size_mm | range | mount |
|---|---|---|---|
| DS18B20 probe | Ø6 × 50 | −55–125 °C | clamp Ø6.15 |
| K-type sheathed | Ø3 or Ø4.8 × 100 | to 1100 °C | clamp Ø3.15 / Ø4.95 |
| K-type bead | 0.3–1 mm wire | to 1000 °C | mica washer |
| hall A3144 / SS49E | TO-92 4.2 × 1.6 × 5 | — | printed mount |
| IR slot sensor TCST2103 | 3.1 mm gap | — | encoder disc Ø60 |
| dial indicator | Ø8 / Ø9.53 stem | 10 mm travel | clamp Ø8.15 / Ø9.7 |

## 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 (7 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/instrument-mounts/index.json

- probe-clamp-ds18b20-6mm: [STEP](https://xemstudio.com/files/hardware/instrument-mounts/probe-clamp-ds18b20-6mm.step) · [STL](https://xemstudio.com/files/hardware/instrument-mounts/probe-clamp-ds18b20-6mm.stl) — split clamp for a Ø6.0 probe/stem (ds18b20 6mm), M3 pinch
- probe-clamp-k-type-3mm: [STEP](https://xemstudio.com/files/hardware/instrument-mounts/probe-clamp-k-type-3mm.step) · [STL](https://xemstudio.com/files/hardware/instrument-mounts/probe-clamp-k-type-3mm.stl) — split clamp for a Ø3.0 probe/stem (k type 3mm), M3 pinch
- probe-clamp-k-type-4-8mm: [STEP](https://xemstudio.com/files/hardware/instrument-mounts/probe-clamp-k-type-4-8mm.step) · [STL](https://xemstudio.com/files/hardware/instrument-mounts/probe-clamp-k-type-4-8mm.stl) — split clamp for a Ø4.8 probe/stem (k type 4 8mm), M3 pinch
- probe-clamp-dial-indicator-8mm: [STEP](https://xemstudio.com/files/hardware/instrument-mounts/probe-clamp-dial-indicator-8mm.step) · [STL](https://xemstudio.com/files/hardware/instrument-mounts/probe-clamp-dial-indicator-8mm.stl) — split clamp for a Ø8.0 probe/stem (dial indicator 8mm), M3 pinch
- probe-clamp-dial-indicator-3-8in: [STEP](https://xemstudio.com/files/hardware/instrument-mounts/probe-clamp-dial-indicator-3-8in.step) · [STL](https://xemstudio.com/files/hardware/instrument-mounts/probe-clamp-dial-indicator-3-8in.stl) — split clamp for a Ø9.53 probe/stem (dial indicator 3 8in), M3 pinch
- 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) — TO-92 hall sensor mount (A3144 / SS49E), M3 foot
- encoder-disc-30-slots-60mm: [STEP](https://xemstudio.com/files/hardware/instrument-mounts/encoder-disc-30-slots-60mm.step) · [STL](https://xemstudio.com/files/hardware/instrument-mounts/encoder-disc-30-slots-60mm.stl) — optical encoder disc Ø60 × 1.5, 30 slots, Ø5.2 bore (for an IR slot sensor)

## Questions

**What are the dimensions of a DS18B20 waterproof probe?**

Ø6 mm stainless sleeve, 50 mm long (a 30 mm version exists), with a 1 m cable; it reads to 125 °C, so it belongs on the cold side.

**What diameter are K-type thermocouple probes?**

Sheathed probes are Ø3 mm or Ø4.8 mm (3/16 in) by 100–150 mm; bare-bead types are just 0.3–1 mm wire and go anywhere up to 1000 °C.

**How do I measure the RPM of a Stirling engine?**

A hall sensor 1–2 mm from a magnet on the flywheel (one pulse per magnet), or a slotted disc through an IR slot sensor; count pulses per second × 60 / pulses per rev.

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