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COMET

Devices

Table of contents

Resources

VISA based instrument communication is handled by class Resource that is used as context manager to guarantee releasing of instrument connections.

# Create and open a bare resource
>>> with comet.Resource("GBIP::1::INSTR") as resource:
...     print(resource.query("*IDN?"))
...
'Keithley, Model 2410, ...'

Class Resource accepts VISA compatible arguments.

# Create a bare VISA resource
>>> resource = comet.Resource(
...   resource_name="GBIP::1::INSTR",
...   visa_library="@py",
...   read_termination="\n",
...   write_termination="\n"
... )

Drivers

Devices are instances inheriting from class Driver using a resource instance Resource for VISA communication with compliant instruments.

COMET comes with a set of various instrument drivers in module comet.driver.

# Create a device using a resource
>>> from comet.driver.keithley import K2410
>>> with comet.Resource("GBIP::1::INSTR") as res:
...     instr = K2410(res)
...     instr.source.voltage = 5.00
...     print(instr.source.voltage)
...
5.0

Registering

Registering resources brings following advantages:

  • Rssources can be accesses using the resources property by any class inheriting from class ResourceMixin.
  • Persistent resource settings can be edited using the main window’s preferences dialog.
  • Stored settings can be applied to registered devices using load_settings().
# Register a device instance
>>> app.resources.add("name", device)
# Access a registerd device
>>> app.resources.get("name")
<comet.Resource object at ...>

Load settings 

app.resources.add("smu", comet.Resource("GBIP::1::INSTR"))
app.resources.add("multi", comet.Resource("GBIP::2::INSTR"))
app.resources.load_settings() # overwrite above resources with persistent settings

Mixins

Inherit from class ResourceMixin to provide access to persistent application settings from within custom classes.

from comet.resource import ResourceMixin

class Custard(ResourceMixin):
    @property
    def spam(self):
        return self.resources.get("spam")

List of classes that inherit ResourceMixin: