Frequently asked questions

Design and Hardware

About design and hardware specifications for working with openQCM

1 – Which is the diameter of the inlet – outlet holes of the window cell?

The openQCM window cell has two holes for tubing connection in application with liquids. If you look closely at openQCM cell window, you can see that the holes are slightly different. One of them is larger than the other. The dimensions of the of the inlet and outlet holes are the following:


  • Inlet dimensions – larger hole
    ID = 0.9 mm
    OD = 1.8 mm
  • Outlet dimensions – smaller hole
    ID = 0.6 mm
    OD = 1.6 mm


The precision machining is mainly due to the CNC milling machine that we used for making the window cell.

openQCM window cell inlet - outlet holes for applications with liquids

openQCM window cell inlet – outlet holes


2 – Which is the best kind of tubing for application with liquids ?

We generally use Tygon® 2375-C high-purity tubing, manufacturer Saint-Gobain part number AJK00002. You can find the tubing technical specifications here

The tubing feautures chemical resistance, clarity and flexibility. They are also unaffected by acids, bases, ketons, slats and alcohols

3 – Which is the best outer and inner diameter of tubing ?

You should use tubing whose outer diameter is OD = 3.2 mm and internal diameter is ID = 1.6 mm.

If you are using openQCM with a peristaltic pump we suggest to use a smaller tube for the one in the peristaltic pump, for example Tygon tubung ID = 0.51 mm. Actually you can reduce the frequency fluctuations by reducing the tube diameter in the peristaltic pump.

4 – Can I use openQCM with a peristaltic pump ?

Yes of course you can ! openQCM is very effective in application with flowing liquids.
You can use the peristaltic liquid  pump designed by Adafruit  product id:1150. It works quite fine with openQCM. You should use an external power supply at 12VDC and connect inlet – outlet tubing for flowing the sample into the openQCM measurement chamber.

5 – What is the material of the 3D printed openQCM case ?

The openQCM 3D printed case is made in Polyamide strong and flexible plastic. This material is very adaptable, it is dishwasher safe and heatproof to 80℃ / 176℉ degrees. You can find the material datasheet here and design guidelines here

6 – What is the thermal properties of the openQCM hardware case ?

The openQCM hardware case is 3D-printed using Polyamide material. It is heatproof to 80°C and higher temperatures may significantly change material properties. The case material datasheet is available at this link


The window cell is made in Poly(methyl methacrylate) PMMA, Plexiglas trade name. The melting point is about 150° C, also you need to pay attention to the coefficient of thermal expansion which is roughly αV = (5–10)×10−5 K−1


The couple of O-rings in the measurement chamber is made in Silicone temperature range -60 to +200°C RS Stock No.527-9790 Brand RS Mfr. Part No.BS011 SIL70 The O-ring datasheet is available at this link


About openQCM shield and Arduino electronics technical specifications

1 – What is the temperature range of the Arduino and openQCM shield ?

It is recommended to use the Arduino board and the openQCM shield in the working temperature range -40°C to 85° C

Where does the thermistor measure the temperature exactly ?

The thermistor actually measures the temperature inside the openQCM device. In fact the thermistor is embedded in the openQCM shield inside the hardware case, between the arduino micro and quartz crystal sensor. It is important to monitoring the temperature because the quartz sensor frequency depends on the variations in temperature.

You can read more about using a thermistor with Arduino to measure the temperature on the openQCM blog

Frequency behaviour

1- Why my frequency baseline are drifiting sometime?

Commonly, in a well set system the drifts are negligible.

In any way, the drift can occur for a number of different reasons.
The most common cause is due to temperature variations. For this reason openQCM mounts a temperature sensor, by which it is possible to verify in real time experimental thermal conditions .



General questions about openQCM the open hardware Quartz Crystal Microbalance

1 – Is openQCM to all effects an high quality scientific instrument?

Absolutely yes! Despite openQCM is a low-cost device its accuracy and stability is fully comparable with most common scientific devices today present in the market.

openQCM is designed by a research team with years of experience in the mass sensors development. As matter of fact, openQCM team collaborate at calibration of QCMs onboard the ESA-ROSETTA space mission and developed a lot of scientific qcm and MEMS devices for space, biology, electrochemistry applications, etc.

2 – Can I use openQCM in air or vacuum?

openQCM is a Quartz Crystal Microbalance whose design was conceived for use in air, in liquid and in vacuum. If you want to use the device in gaseous environment it is sufficient to remove the magnetic sealing chamber. So you will be able to use openQCM without further modification.

3 – Can I use openQCM for educational purposes?

The high affordable cost and its  easy of use makes openQCM the best choice for educational purposes. For degree student or for every level of school, this Quartz Crystal Microbalance device will increase the learning experience.


About how to install arduino driver and openQCM software.

1 – The Arduino COM port is not recongnized. What should I do ?

You should update the Arduino driver. You can download the Arduino driver at this link Unzip the folder and install the drivers.


Windows 8 OS driver digitally signed known issue
Sometimes Arduino is not recognized by Windows 8, because the driver is not digitally signed. In this case you should follow this tutorial

2 – I can’t upload the Arduino firmware. What should I do ?

Firstly you should verify that the Arduino driver is correctly installed on your computer.
If the Arduino driver is ok, in order to upload the openQCM arduino skecth you should add the external library FreqCount developed by Paul  Stoffregen. Download the FreqCount library at this link and follow the Arduino guide Installing Additional Arduino Libraries in order to install the library.

3 – Is openQCM software cross-platform ?

Yes it is. openQCM application software runs on the most common operating system Windows, Mac and Linux.  For more info please follow the installation guide