# openQCM Wi2

> Source page: https://openqcm.com/about-openqcm-wi2
> Markdown version for AI agents and readers of plain text. Site guide: https://openqcm.com/llms.txt · Everything in one file: https://openqcm.com/llms-full.txt

_Benchtop · frequency QCM · USB-powered, wireless-ready_

openQCM Wi2 is the frequency QCM in its plainest form: a Pierce oscillator keeps the crystal ringing, a microcontroller counts its cycles for one second, and that count is the measurement. Small enough for one hand, simple enough for a classroom, open down to the last screw.

## Key figures

- 43 g: weight
- 66 × 50 × 26 mm: main dimensions
- 1 s: typical gate time
- ~50 µl: measurement chamber

## The principle: An oscillator, not a sweep.

A Pierce oscillator built on an SN74LVC1GX04 inverter locks onto the crystal's fundamental resonance and follows it on its own. The microcontroller counts the edges of that signal over a fixed gate, typically one second. What comes out is the resonance frequency, with the crystal temperature from an MCP9808 sensor pressed against it. Wi2 measures frequency only, at the fundamental: for dissipation and overtones, see Q-1 and NEXT.

## The sensor module: Pogo pins, a lever and a magnet.

The 14 mm wrapped-electrode crystal rests on two pogo pins, contact side down. A lever sets the O-ring pressure finely, and a small magnet keeps the temperature sensor against the crystal. The cell holds about 50 µl; its only wetted parts are the window (PMMA or PTFE) and an FKM (Viton) O-ring.

## Open hardware: Eight printed parts and one board.

The case is eight SLS-printed nylon PA2200 parts and a CNC-cut window; the main board is a two-layer 59.9 × 36.8 mm PCB with a Teensy microcontroller. The 45-page assembly manual goes through every step, from cutting the O-ring that cradles the crystal to the final leak test.

## Connectivity: USB today, wireless when you want it.

Power and data travel on one micro-USB cable at 5 V. Expansion headers on the board take a Wi-Fi module or a PCB of your own: Wi2 is wireless-ready rather than wireless out of the box. The software tells devices apart by their port, so several Wi2 can run on one computer, a whole bench of them in a teaching lab.

## Validation: What every unit has to pass.

Each assembled unit is tested with a 10 MHz AT-cut crystal, at least 30 minutes in air and 35 minutes in static deionized water, in a 20–30 °C room. Acceptance: frequency standard deviation ≤ 1.0 Hz in air and ≤ 1.5 Hz in liquid, crystal temperature stable within ±0.1 °C, equilibrium in about 10 minutes in air and 20 in liquid.

## Specifications

### Sensor

- **Crystals:** 5 and 10 MHz, 14 mm, wrapped electrode (single-side contact)
- **Chamber:** ~50 µl
- **Wetted parts:** PMMA or PTFE window, FKM (Viton) O-ring

### Measurement

- **Quantity:** Frequency, at the fundamental
- **Method:** Pierce oscillator (SN74LVC1GX04) and hardware frequency counter
- **Gate:** Typically 1 s
- **Temperature:** MCP9808 against the crystal, ±0.25 °C typical
- **Dissipation:** No (see Q-1 and NEXT)

### Build

- **Case:** Nylon PA2200, SLS-printed
- **Dimensions:** 66 × 50 × 26 mm
- **Weight:** 43 g
- **Power:** USB, 5 V
- **Wireless:** Expansion header for a Wi-Fi module or custom PCB

### Software

- **Licence:** Open source
- **Data:** Frequency and temperature in real time, saved to text files
- **Systems:** Windows, macOS, Linux

## Related pages

- [Design](https://openqcm.com/openqcm-wi2-design/)
- [Electronics](https://openqcm.com/openqcm-wi2-electronics/)
- [Software](https://openqcm.com/openqcm-wi2-software/)
- [Tech specs](https://openqcm.com/openqcm-wi2-tech-specs/)
- [Gallery](https://openqcm.com/openqcm-wi2-gallery/)

## Downloads

### Software

- [Executable for Windows](https://openqcm.com/downloads/wi2/software/openqcm-wi2-software-2.1-windows.zip) (ZIP)
- [Software user manual](https://openqcm.com/downloads/wi2/software/openqcm-wi2-software-2.1-user-manual.pdf) (PDF)

### Firmware

- [Teensy 4.0 firmware](https://openqcm.com/downloads/wi2/software/openqcm-wi2-firmware-1.2-teensy4.zip) (ZIP)

### Docs

- [User manual](https://openqcm.com/downloads/wi2/openqcm-wi2-user-manual.pdf) (PDF)

## Buy or ask

- Store: https://store.openqcm.com/
- Contact: https://openqcm.com/contacts/

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openQCM by Novaetech S.r.l., Pompeii, Italy · Buy: https://store.openqcm.com/ · Contact: info@openqcm.com · https://openqcm.com/contacts/