fsc2: 6.22 Goniometer Functions

6.22 Goniometer Functions

A single module for a computer controlled goniometer exists:

er218: Bruker ER218 PG1, needs a a Meilhaus card with DIO capabilities and a bit of one-built electronics

To use the module in an experiment put its name into the DEVICES section of the EDL script. Please note that the name of the module for the DIO device (Meilhaus DIO subsystem) must be listed before this module.

List of goniometer functions:

`goniometer_name()'
`goniometer_angle()'
`goniometer_increment_angle()'
`goniometer_backslash_correction()'
`goniometer_reset()'
`goniometer_set_zero_angle()'

Descriptions of goniometer functions:

`goniometer_name()'

Returns a string with the name of the goniometer being used.

`goniometer_angle()'

This function allows to either query the angle the goniometer is at or to move it to a new angle. If called without an argument the function returns the angle (in degrees) it is at the moment. If called with an (floating point) argument this is taken to be the new angle (in degrees) to move the goniometer to. The new angle must a multiple of 0.125 degree, otherwise the nearest angle to the specified value is used. The function return value is the new angle the goniometer is set to.

Please note: Setting a new angle may take some time and the operation cannot be stopped until the goniometer has arrived at its new position.

This function can only be used in the EXPERIMENT section.

`goniometer_increment_angle()'

The function expects a single argument, which is taken as the angle (in degres) by which the goniometer is to be rotated. Both positive (for clockwise) and negative (for counterclockwise rotation) values are allowed, but they must be multiples of 0.125 degrees (or the argument is adapted to the nearest possible increment angle). The function return value is the new angle the goniometer is set to.

Please note: Changing the angle may take some time and the operation cannot be stopped until the goniometer has arrived at its new position.

This function can only be used in the EXPERIMENT section.

`goniometer_backslash_correction()'

The goniometer has some mechanical backslash which reduces the the absolute angular accuracy to about 0.5 degree. To increase this acurracy backslash correction can be switched on - in this case when the goniometer is moved counterclockwise it will move to some angle a bit below the angle requested by the functions goniometer_angle() or goniometer_increment_angle() and only then in a clockwise direction to the requested angle.

If called with an argument of 1 or the string "ON" backslash correction is switched on, while when called with an argument of 0 or the string "OFF" it's switched off again. Switching backslash correction one may introduce a down and up rotation of the goniometer.

Please note: Switching backslash correction on may lead to somewhat longer times required to go to a new angular position.

`goniometer_reset()'

This function can be called to move the goniometer to built-in zero position. After a call of this function (which doesn't expect any arguments) angles used as arguments or returned by the function goniometer_angle() are relative to this zero position. Please note that calling this function requires at least 72 s and that it can't be stopped once the command has been issued.

This function can only be used in the EXPERIMENT section.

`goniometer_set_zero_amgle()'

This function, taking no arguments, allows to set a new zeqro position of the goniometer, i.e. angles used as arguments or returned by the function goniometer_angle() later on are relative to this new zero position.

This function can only be used in the EXPERIMENT section.

This document was generated by Jens Thoms Toerring on September 6, 2017 using texi2html 1.82.