Sequencer

The sequencer is the heart of SweepMe!. Use it to create tree-like measurement sequences. Items can be placed by drag&drop from a list of all available Modules. There exists basic examples (Settings -> Load Example) that demonstrate the creation of measurement procedures.

Procedures

The sequencer presents a measurement in a tree-like hierarchy of modules. Each module can be understood as a for-loop over its sweep values. These sweep values can be seen as set values that have to be applied and reached to perform a measurement point. Whenever modules are nested into each other, it automatically means that nested for-loops are created. As for any tree, there exist branches. If you have a single branch, all items are nested into each other. This is the most simple and basic configuration you can realize. In this case, SweepMe! will perform variation across all combinations of set values of each module in the branch. Each combination can be seen as a measurement point for which all modules of the sequencer are asked for their measurment values. These measurement values are typically different from the set values. For example, a source measuring unit could have a set value of 5 Volt but the meausurement value might be 4.99 Volt.

The order of the modules directly infuences the measurement procedure: It makes a difference whether you want to measureme at all defined voltages for each temperature or if you want to measure at all defined temperatures for each voltage. In contrast, taking measurement values only slightly depends on the modules as all modules of a branch are read out at each measurement point.

If you put items on the same level of hierarchy (siblings), you will automatically create a second branch of the tree. Now, SweepMe! will run through the first branch, followed by the second branch. Only the modules of the current branch are used to apply the sweep values and readout the measurement values. Of course, these two branches might have some modules in common and these modules will take part at the measurement of both branches. Please see the example below:

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 hierachy of the sequencer tree, i.e. they will be swept consecutively.

The measurement will then have the following sequence:

1. SMU1 applies the first sweep value of the sweep.
2. SMU2 will run its full sweep and SMU1 and SMU2 are measured (while SMU3 is still off).
3. SMU2 is switched off and now SMU3 runs its full sweep and SMU1 and SMU2 are measured (while SMU1 is off).
4. SMU3 is switched off.
5. SMU1 applies the next sweep value of its sweep (or the measurement is finished, if no further values shall be swept).

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

Module categories

The invisible root module 'Time'

The sequencer has an invisible root item called 'Time' being part of any procedure. It measures the elapsed time and generates a time stamp. You will find it for example in your saved data as well as if you configure a widget such as Plot.

Basic modules

There are basic modules that are used in almost any type of measurement: Loop, Hold, or MakeFile. Have a look at the examples to understand their meaning. We also recommend to just play around with these modules to understand how they work and interact. For example, try to combine multiple Loop or MakeFile to see the sequence of the measurement and the generated data files.

Device modules

Some modules can be used to implement measurement equipment via a Device Class. These modules have field 'Device' that allows to select the Device Class.

SMU, Signal, Spectrometer, Scope, LCRmeter, LockIn, Monochromator

Add-on modules

SweepMe! can be extended into any direction to implement individual setups, devices and tasks. Contact us to discuss your specific needs.

Handling

Adding items

Items are added by drag&drop from the right sided list of all available Modules. Some modules generate a new tab, other modules have a hidden dialog. In both cases, the module can be configured, by double-clicking on it.

Moving items

Just drag&drop an item including all child items to a new position in the sequencer. If you like to insert the item between two other items at the same hierarchy, a thin black line must appear between the two items.

Removing items

You can remove an item from the sequencer by selecting it and pressing 'Del(ete)'. An alternativ would be to right-click on the item and click 'Delete selected item(s)'

Tree terminology

Root

The root of the sequencer is always an invisible module called "Time". It is part of any measurement and is part of any branch that you add to the sequencer. Thus, you will always have a timestamp in your measurement data.

Child

A child module is the module that is inserted to a certain module.

Parent

The parent module is the module into which a module is inserted in.

Leaf

A leaf of the sequencer is always a module that has no child items, i.e. no module is inserted to it.

Branches

Each module that is a leaf defines a new branch. A branch is therefore given by all modules that are between the invisible root module Time and the leaf module. Modules can be part of several branches simultaneously. Modules that are part in multiple branches perform the measurements that are defined in each branch. The number of leaf modules is always the number of branches.

Siblings

Modules that have exactly the same parent module are siblings. If you have siblings in your sequencer, you automatically have multiple branches.

Setting and reading values

All items have at least one Sweep 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 set values, e.g. a Source-Measure-Unit SMU typically has several values in order realize a current-voltage curve.

When reading out the sequencer, the Sweep values of each item are iterated, and for each Sweep 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 Sweep value and reading a Measurement value!

Setting a Sweep value: Whenever set values of an item are iterated, they are forwarded to their Modules to be applied. 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 Measurement 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 arrangement of the items in the current branch, all items are read out. The major difference is the order in which the devices are called, the order in which the data is saved into the file, and the order in which items appear in various combo boxes.

Settings

Procedures, as defined by modules in the sequencer, can be saved and restored via a setting.