Excess rotor vibration decreases production quality and causes unscheduled maintenance breaks in the manufacturing industry utilizing rotating machinery in production. Measuring and monitoring the rotor vibration levels in production conditions provides added value through decreased maintenance costs and quality variations. E.g., paper and metal manufacturing are fields where the rotor running accuracy affects directly to the quality of the final product. In few production machines, critical components are equipped with a modern wired condition monitoring system to acquire vibration signals from the bearing housings during operation. However, upgrading a running production machine with this kind of system is expensive and requires a maintenance brake. In the present study, a low-cost MEMS accelerometer sensor and wireless data transmitter were attached to a bearing housing of a large rotor. Measurement series was conducted to determine the subcritical vibration spectrum and the results were verified against a laboratory vibration measurement instrument. The vibration was measured during a rotor acceleration mimicking a production ramp-up.