Enhancing openQCM Quartz Crystal Microbalance Frequency Stability and Power Consumption

Easy solution for enhancing the frequency stability and reducing the power consumption of openQCM the open source quartz crystal microbalance.

Pierce oscillator electronic circuit quartz crystal microbalance

Pierce oscillator circuit basic design  for quartz crystal microbalance.

We are performing the latest tests on openQCM and we have found an easy solution for enhancing the quartz crystal frequency stability and at the same time reducing the electric power consumption.

We are using a quartz crystal oscillator driver which incorporates an unbuffered inverter plus an inverter into a single device and it is optimized for crystal oscillator applications in a wide range of frequency. The openQCM electronics is designed to make use of the oscillator driver in a typical configuration also known as Pierce oscillator circuit.

The oscillator driver is optimized to work at 3.3 V supply voltage, ±24 mA output current. These working conditions ensure high frequency stability and low power consumption. Arduino Micro has a 3.3 V supply generated by the on-board regulator, maximum current draw is 50 mA. So the 3.3 V pin is well-suited to power the oscillator driver.

We have observed some frequency noise and overheat when powering the quartz oscillator driver via Arduino Micro 5V power pin. The Arduino board is powered by the USB connection, whose current is not regulated and depends on the power shared by the host PC. This is the main cause of quartz oscillator frequency noise. Instead the 3.3 V pin is regulated also when Arduino Micro is powered vis USB. Moreover the oscillator driver is powered at the right working conditions causing the minimum power consumption. This is the easiest solution showing great improvements of openQCM performances.