openQCM Holder · Vacuum-compatible QCM holderThe board is the housing.
openQCM Holder has no case. Three layers of FR-4, the glass-epoxy of circuit boards, are at once the structure, the crystal seat and the wiring. Under 5 grams and 4 mm thin, with no plastic housing, it carries a QCM crystal from the open bench into a vacuum chamber.
- weight
- < 5g
- thickness
- 4mm
- without the plug
- 25 × 18.6mm
- crystals, 14 mm
- 1–10MHz
Electronics as structure.
Three FR-4 layers clamp a 14 mm wrapped-electrode crystal (1 to 10 MHz) and carry its contacts, an MCP9808 temperature sensor on I²C (−40 to +125 °C) and a Pierce oscillator whose output is a TTL signal at the crystal's resonance frequency. Building the holder from circuit board removes the plastic housing, and with it a source of mechanical play.
A plug, or seven gold pads.
The USB version plugs into your own acquisition electronics through a USB 3.0 connector with its own pinout. The pad version is made for soldering: seven gold pads take the wires of a vacuum feedthrough, so only the holder sits inside the chamber.
Never plug the USB version into a computer. The connector is a USB 3.0 plug, but its pins carry the crystal, the oscillator output and the I²C bus, not USB: a standard port can damage the holder.
| Pin | Signal | Use |
|---|---|---|
| 1 | SDA | I²C data, temperature sensor |
| 2 | QCM OUT | Crystal |
| 3 | QCM IN | Crystal |
| 4 | NC | Not connected |
| 5 | SIG OUTPUT | Oscillator output |
| 6 | GND | Ground |
| 7 | V+ | Supply |
| 8 | GND | Ground |
| 9 | SCL | I²C clock, temperature sensor |
| Pad | Signal | Use |
|---|---|---|
| 1 | GND | Ground |
| 2 | QCM IN | Crystal (SENS−) |
| 3 | SCL | I²C clock, temperature sensor |
| 4 | SIG OUTPUT | Oscillator output |
| 5 | SDA | I²C data, temperature sensor |
| 6 | QCM OUT | Crystal (SENS+) |
| 7 | V+ | Supply |
Same signals, different order: on the plug the crystal is on pins 2–3, on the pads on 2 and 6. Check twice before you solder.
What the manual says, and what it does not.
All-FR-4 construction makes the holder suitable for atmospheric and vacuum environments. The manual gives no pressure range, outgassing figure or bake-out temperature: check them for your process, and keep the rest of the electronics outside the chamber.
- 01Custom setups on the bench
- 02OEM integration in your instrument
- 03Vacuum chambers, through a feedthrough
- 04Educational kits
The data sheet.
From the official manual. Where two documents disagree, the figure is left out until it is confirmed.
Sensor
- Crystal
- Single, 1–10 MHz, 14 mm, wrapped electrode
- Electronics
- Pierce oscillator, TTL output
- Quantity
- Frequency
- Temperature
- MCP9808 on I²C, −40 to +125 °C
Mechanics
- Material
- FR-4, three PCB layers
- Size
- 25 × 18.6 × 4 mm; 40.2 mm long with the plug
- Weight
- < 5 g
Electrical
- Connection
- USB 3.0 plug (custom pinout) or gold solder pads
- Supply
- 3.3–5 V
- Current
- Max 80 mA at 5 V
Put a QCM in the chamber.
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