1. What should I check if my MAS probe won’t spin up or seems to stall at low speeds? A video demonstrating MAS probe spinning is available via the link provided.
We’ll address the low-speed stalling issue first.
Sometimes a rotor may appear to “stick” at a low spinning speed. This is often caused by a resonance in the rotor, which can result from uneven sample distribution or another imbalance. Follow the video link provided to see how to overcome this resonance and continue bringing the rotor up to speed.
For other spinning problems:
Unbalanced samples. The most common cause is a poorly packed or unbalanced sample. Samples should be finely powdered to avoid dense lumps collecting asymmetrically along the inside wall of the rotor. Add the sample as evenly as possible, then spin the rotor slowly for a couple of minutes to allow the sample to “spin pack” before gradually increasing the speed.
Excessive turbine cap wear. Another fairly common issue, especially with probes that have been in use for some time, is excessive turbine cap wear. Turbine caps can wear from both spinning and handling during the loading process. Inspect the cap under a magnifying glass for signs of wear. If possible, compare it with a new cap.
Excessive rotor wear. Less commonly, excessive rotor wear may be the cause. This is usually the result of spinning an unbalanced sample for an extended period of time. In severe cases, rotor wear may also cause stator wear, and the probe may need to be returned to the factory for service.
If a empty rotor still does not spin properly with a new set of turbine caps, there may be a problem with the probe itself, and factory service may be required.
