spec

Software for Diffraction

4.5. - Freezing Angles



For the "omega-fixed" , "phi-fixed" , "zone" , "azimuth-fixed" , "alpha-fixed" and "beta-fixed" modes you may freeze the value of the associated angle (or angles), so when calculating motor positions corresponding to an arbitrary (H,K,L) using calcA (within br, for example), the angle (or angles) will be reset to the frozen value before the calculation no matter what the current position of the diffractometer.

The macro freeze waits until all motors have stopped moving, then sets a variable (g_frz) indicating frozen mode is on and saves the current position of the frozen angle in another variable. Usage might be:
1.FOURC> setmode 1
Now using Omega-Fixed mode. 2.FOURC> freeze 5
Sun Jan 28 12:16:23 1990. Freezing Omega at 5. 3.FOURC>

If the value to freeze for the current mode is not given as an argument to the macro, the current value of the related angle or parameter is used to set the frozen value. In zone mode, both the χ and φ values need to be given as arguments.

The macro unfreeze sets g_frz to zero. Subsequent angle calculations will use whatever the current value of the associated constrained angle or angles for the current mode.