# openQCM Q-1 · Electronics

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_openQCM Q-1 · sheet 04 · Electronics_

The openQCM Q-1 electronics is mainly comprised of a network analyzer, which passively interrogates the quartz sensor by sweeping the frequency around its resonance.

## The signal path

AD9851 DDS (steps the drive frequency around the chosen harmonic) → Quartz crystal (in the sensor module, on two pogo pins) → AD8302 (gain and phase across the crystal) → Teensy (ADC with 13-bit effective resolution over 3.3 V) → USB (curves to the Python software)

## Measure the crystal, nothing else.

The actuation signal is generated via the AD9851 DDS/DAC frequency synthesizer, and the resulting output is detected by the AD8302 gain-and-phase detector — quantifying both the gain across the quartz crystal and the phase difference between actuation and output signals.

Analyzing the gain curve characterises the sensor through concurrent measurement of resonance frequency and quality factor. A significant advantage of this approach is its ability to assess quartz parameters independently, mitigating interference from external circuitry.

![The openQCM Q-1 network analyser shield](https://openqcm.com/wp-content/uploads/2023/05/Quartz-Crystal-Microbalance-openQCM-Q-1-Shield-Photo.png)

## The boards

- **Main board:** 2 layers, 82.9 × 60.2 mm, FR-4 TG150, 1.6 mm, 1 oz copper, ENIG
- **Key parts:** AD9851 DDS, AD8302 gain/phase, AD5252 digital potentiometer, LM7301 op-amp, two LP2985 regulators (5 V and 3.3 V), precision clock oscillator
- **Parts count:** 72 components on the main board
- **RF connectors:** 2 SMA (optional)
- **Proximity board:** 31 × 29 mm, MCP9808 (±0.25 °C), two pogo pins, status LED, USB 3.0 connector to the main unit
- **Schematics:** Open source

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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/