2.2.2.1. DAQ Move

This module is to be used to control any Actuator hardware. An Actuator is, in a general sense, any parameter that one can control and may vary during an experiment. The default actuator is a Mock one (a kind of software based actuator displaying a position and accepting absolute or relative positioning).

2.2.2.1.1. Introduction

This module has a generic interface in the form of a dockable panel containing the interface for initialization, the manual control of the actuator position and a side tree like interface displaying all the settings. Fig. 2.6 shows the minimal interface of the module (in order to take minimal place in the Dashboard)

daq_move_gui_base

Fig. 2.6 Minimal DAQ_Move user interface

2.2.2.1.2. Hardware initialization

  • Actuator: list of available instrument plugins of the DAQ_Move type, see Fig. 2.7.

  • init: Initialize the hardware with the given settings (see Instrument Plugins for details on how to set hardware settings.)

  • quit: De-initialize the hardware and quit the module

daq_move_gui_base

Fig. 2.7 Menu list displaying the available instrument plugin of type DAQ_Move

2.2.2.1.3. Positioning

Once the hardware is initialized, the actuator’s value is displayed on the Current value display (bottom of Fig. 2.6) while the absolute value can be set using one of the top spinbox (respectively green or red) and apply it using respectively the green_arrow or red_arrow button. This double positioning allows to quickly define two values and switch between them.

2.2.2.1.4. Advanced positioning

More options can be displayed in order to precisely control the actuator by pressing the plus_button button. The user interface will then look like Fig. 2.8.

daq_move_gui_rel

Fig. 2.8 DAQ_Move user interface with finer controls

The two new displayed spinbox relate to Absolute positioning and Relative one.

  • home: the actuator will try to reach a home position (known position or physical switch limit)

  • abs: the actuator will try to reach the set absolute position

  • move_rel: the actuator will try to reach a relative position (+increment)

  • move_rel_m: the actuator will try to reach a relative position (-increment)

  • where: will update the current actuator’s value display

  • stop: stop the current motion (if possible)

2.2.2.1.5. Settings

The hardware and module settings can be displayed by pressing the settings button. The user interface will then look like Fig. 2.9.

daq_move_gui_settings

Fig. 2.9 Full DAQ_Move user interface with controls and settings

In the settings tree, there is two sections. The first relates to the Main settings of the actuator while the second relates to the hardware settings (the ones the hardware will need in order to initialize…). There is also specific settings explained below.

(not much there for the moment apart for the selected stage type and Controller ID that is related to multi-axes controller.

2.2.2.1.5.1. Main Settings

  • Actuator type: is recalling the instrument plugin class being selected

  • Actuator name: is the name as defined in the preset (otherwise it is defaulted to test)

  • Controller ID: is related to multi-axes controller (see Multiaxes controller)

  • Refresh value: is the timer duration when grabbing the actuator’s current value (see Configuration file).

2.2.2.1.5.2. Multiaxes controller

Sometimes one hardware controller can drive multiple actuators (for instance a XY translation stage). In the simplest use case, one should just initialize the instrument plugin and select (in the settings) which axis to use, see Fig. 2.10.

daq_move_gui_settings

Fig. 2.10 Selection of one of the axis this controller is able to drive.

Then the selected axis can be driven normally and you can switch at any time to another one.

It is more complex when you want to drive two or more of these multi-axes during a scan. Indeed, each one should be considered in the Dashboard as one actuator. But if no particular care is taken, the Dashboard will try to initialize the controller multiple times, but only one communication channel exists, for instance a COM port. The solution in PyMoDAQ is to identify one actuator (one axis) as Master and the other ones will be referred to as Slave. They will share the same controller address (and actual driver, wrapper, …) represented in the settings tree by the Controller ID entry. These settings will be activated within the instrument plugin class where one can define a unique identifier for each actuator (U or V for the conex in Fig. 2.9).

  • Controller ID: unique identifier of the controller driving the stage

  • is Multiaxes: boolean

  • Status: Master or Slave

  • Axis: identifier defined in the plugin script

These settings are really valid only when the module is used within the Dashboard framework that deals with multiple modules at the same time as configured in the Preset manager interface.

2.2.2.1.5.3. Bounds

if this section is activated (by clicking the Set Bounds entry) then the actuator positions will be software limited between min and max. This can be used to prevent the actuator to reach dangerous values for the experiment or anything else.

2.2.2.1.5.4. Scaling

If this section is activated (by clicking the Use scaling entry) then the set and displayed positions will be scaled as:

new_position=scaling*old_position+offset

This can be useful for instance when one deals with translation stage used to delay a laser pulse with respect to another. In that case it is easier to work with temporal units such as femtoseconds compared to mm or other native controller unit.

2.2.2.1.5.5. Other settings

  • epsilon: -very important feature- the actuator will try to reach the target position with a precision epsilon. So one could use it if one want to be sure the actuator really reached a given position before moving on. However if the set precision is too small, the actuator may never reached it and will issue a timeout

  • Timeout: maximum amount of time the module will wait for the actuator to reach the desired position.

2.2.2.1.6. Configuration file

A dedicated entry is present in the toml main configuration file for the DAQ_Move to tailor the module’s behaviour. The various field are written below together with their meaning

[actuator]
epsilon_default = 1
polling_interval_ms = 100
polling_timeout_s = 20  # s
refresh_timeout_ms = 500  # ms
siprefix = true
display_units = true

  • epsilon_default: default value for the actuator precision

  • polling_interval_ms: interval in millisecond for refreshing the actuator’s value

  • polling_timeout_s: Timeout in seconds during which the DAQ_Move tries to reach its target

  • refresh_timeout_ms: interval in millisecond for probing the actuator’s value in continuous mode

  • siprefix: tell if printing of current value use a SI prefix or not (µ, m, k, M…)

  • display_units: display units in the SpinBoxes