MAS Control Unit:

Air supply requirement:

1. Oil free,   particle  size < 0.01 micron  

2. Dew Point  < -30 ⁰C

3. Working Pressure  6 - 8 bar (87 - 114 psi)

4. Flow rate: 4 m³ /hr  (2.35 cu ft./min)

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Rotor: The sample is contained is a special tube which rotates at high speed. The diameter of the rotor will be determined by the probe diameter and it can currently be 4mm.

 Stator: The rotor is spun inside a specially designed housing called a stator located at the top of the probe. This housing remains static during the rotation. Pressure streams know as the Drive Pressure (DP) and Bearing Pressure (BP) are directed onto the rotor by means of the stator.

Two types of rotor material are normally used.

Silicon Nitride (grey in color)

Zirconia (white / yellow)

MAS Stator.

A Bearing pressure is used to levitate the rotor within the stator on a cushion of air. This enables practically frictionless rotation in that there is no physical contact between the rotor and the stator. The actual rotation is achieved by the application of the Drive pressure. Successful stable rotation can only be achieved with a combination of the correct Bearing and Drive pressure which is controlled by the pneumatic unit. A sudden loss of Bearing Pressure is the most dangerous scenario in terms of rotor and stator damage as the levitation would be suddenly removed and the rotor would crash against the stator while still spinning. For this reason a Sense of Bearing measurement is used to ensure that the Bearing pressure is sufficiently high at all times. The Bearing Sense pressure sensor is located at the base of the probe. If insufficient BP is detected (for example due to a leak in an air hose) then the DP, which effectively rotates the sample, will be immediately reduced.

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Last updated: February 05, 2003.