A3

The Angle of the Sample

System Name: SmplTheta

Type: Virtual

Brief Description

This device controls and maintains the angle of the sample by controlling the 
angle of rotation stage mounted on the kidney.  Whenever A3 is commanded to a new
destination it will keep the sample at the new destination angle even when the kidney 
is later rotated, by automatically counter-rotating.  

For alignment purposes a zero can be specified for A3 using standard methods for
setting zeros on devices (command: Device Set ...).  The zero specifies the angle
A3 is at when the kidney and rotation stage are both at 0.

There are a few cases where it is ambiguous what A3's the last commanded destination
is.  These are listed below with explanations:

    On startup:
        The angle of A3 is recorded when the system starts, this angle is considered
        this initial commanded destination for A3 and will be maintained automatically 
        when the kidney is moved.
    
    When baseSampleTheta is moved directly:
        After baseSampleTheta is moved, the final angle of A3 is recorded and
        from then on this new angle of A3 is considered the last commanded destination.
        
        This avoids the following potentially confusing situation:
        
        The user commands A3 to position 20.
        The user later moves basesampletheta directly resulting in A3's position 
        being at 15.
        Later still the user directly/indirectly moves the kidney, A3's position will
        stay at 15 rather than suddenly moving to 20.
        
    When A3 is stopped during a move:
        Once stopped the angle of A3 is recorded.  This angle is considered
        the last commanded destination and will be maintained from that point on.

        

Restrictions

Devices which cannot be moved simultaneously with this device:

Other Restrictions:

None

Interactions

Devices which affect this device:

Devices which are affected by this device:

Whenever A3 is moved:
    
    BaseSampleTheta is moved based on the follow formula:
    
    BaseSampleTheta = A3 - Kidney - (A3's zero)
    
    If in UB Matrix mode HKL is recalculated, other wise HKL is assigned the value N/A.