A hydraulic excavator is one of the most used machines in mining, construction and geotechnics. Monitoring its productivity can provide benefits such as savings in fuel consumption and maintenance, cost optimization of working parameters and a higher working efficiency. A measurement system for such a purpose can be complex and expensive, as it requires special equipment from the manufacturer and does not exist as an out of the box solution that would measure working parameters such as bucket trajectory, digging energy, digging force, etc. A measuring system was designed to monitor productivity and gather working parameters. It consists of three pressure transmitters for measuring cylinder pressures, three draw wire sensors for cylinder elongations, one inertial measurement unit for the measurement of swing angle and one logger unit for data acquisition and storage. The logger unit, equipped with an SD card module and 12-bit AD converter, is based on Atmega328 microcontroller, which allows for the usage of Arduino IDE and already developed libraries. The system was tested in a laboratory to determine its accuracy, resolution and usable sample rate. Cylinder pressure can be measured in the range of 0-500 bar with an excellent accuracy of 0.026 % FSO and 0.15 bar resolution. Cylinder elongation can be measured in the range 0-2300 mm with an accuracy of 0.087 % FSO and 0.58 mm resolution. Swing angle measurement accuracy is 1.2° per circle or 0.33 % FSO. The usable sample rate of the system is found to be 39 Hz-588 Hz, depending on the logger executing code.