Sequencer

The sequencer is a SweepMe! tool to create your own sequence of measurements. Items can be placed by drag&drop from a list of all available items/measurements and deleted by selecting them folowed by pressing 'Del(ete)' on the keyboard. Each item represents either a measurement communicating with an external device or a certain internal procedure doing some operation like MakeFile, or PlotData.

The sequencer presents all measurements in a tree like hierarchy. The more they are shifted to the right side, the lower the level of hierarchy. The structure of the tree allows for serial and parallel arrangement of the items. Thus, very complex measurement scenarios can be created.

Serial arrangement: Items only have either one parent item of higher hierarchy, one child item of lower hierarchy, or both.

Parallel arrangement: Multiple items are placed at the same level of hierarchy.

In general, a full measurement sequence can be represented by various serial arrangements and parallel arrangements. Whenever a parallel arrangement is created, the tree gets new branches which are individually processed. For simple measurements, we recommend to avoid parallel arrangements and solely create serial arrangements

Example

Visualization of the traversing of the sequencer which has a device with two consecutive children.

Let's consider a sequencer arrangement with three SMUs where SMU 1 has two direct subelements, SMU 2 and SMU 3. SMU 2 and SMU 3 shall be at the same depth of the sequencer tree, i.e. they will be swept consecutively.

The measurement will then have the following sequence:

1. SMU 1 applies the first value of the sweep
2. SMU 2 will run its full sweep, while SMU 3 is still off
3. SMU 2 is switched off and now SMU 3 runs its full sweep
4. SMU 3 is switched off
5. SMU 1 applies the next value of its sweep (or the measurement is finished, if no further values shall be swept)
6. Repeat the process starting with 2.

This measurement process is shown schematically in the animation on the right.

Setting and reading

All items have at least one set value which will be used to indicate their presence in the tree, and to make them participating in the read out of the sequence. Some items, however, have multiple values, e.g. a Source-Measure-Unit SMU typically has several values in order realize a current-voltage curve.

When reading out the sequence, represented by the tree, the values of each item are iterated, and for each value of one item, the prior procedure is again done for the children items which are below in the hierarchy of the tree.

There is a crucial difference between setting a value and reading a value!

Setting a value: Whenever values of an item are iterated, they are forwarded to their Measurement Classes. As a consequence, the sequence of items, has a crucial impact on the measurement procedure, i.e. in which order parameters are applied to your devices.

Reading a value: Whenever the end of a branch of the tree is reached, reading of the device parameters is started. Standardized SweepMe! functions are called in order to apply, measure, and call the parameters of all items of the current branch of the tree. Thus, independent of the exact serial arrangement in the current branch, all items are read out. The major difference is the order in which the device are called, the order in which the data is saved into the file, and the order in which items appear in various combo boxes.

If only one item has multiple values and a purely serial arrangement is used, the position of each item, except of MakeFile and PlotData, can nicely be used to adjust the order of setting and reading parameters.