Select a Signal Kind¶

Prerequisites¶

• You are writing a custom ophyd device class for BEC.

1. Choose the signal purpose¶

For each signal, the Kind attribute decides how the signal is treated in runtime. Most of the time we can classify your device signals into three categories:

• Primary monitored readings, use Kind.hinted and Kind.normal
• Configuration values, use Kind.config
• Internal controls, use Kind.omitted

In the ophyd read interface, this maps to:

• read() includes Kind.hinted and Kind.normal.
• read_configuration() includes Kind.config.
• Kind.omitted is excluded from both.

2. Setup your device class¶

When defining your custom ophyd device, set the kind argument of each signal component to the appropriate Kind value based on its purpose. For example:

from ophyd import Component as Cpt, Device, Signal, Kind


class MyDetector(Device):
    # Primary scan value
    counts = Cpt(Signal, name="counts", kind=Kind.hinted)

    # Additional scan value
    elapsed_time = Cpt(Signal, name="elapsed_time", kind=Kind.normal)

    # Configuration metadata
    acquisition_time = Cpt(Signal, name="acquisition_time", kind=Kind.config)

    # Internal control signal
    acquire = Cpt(Signal, name="acquire", kind=Kind.omitted)

3. Verify the result¶

After loading your device:

• Check device.read() and confirm only scan signals appear.
• Check device.read_configuration() and confirm setup signals appear.

det = MyDetector(name="det")

det.read()
OrderedDict([('det_counts', {'value': 0.0, 'timestamp': 1775030964.884717}),
             ('det_elapsed_time',
              {'value': 0.0, 'timestamp': 1775030964.884744})])

det.read_configuration()
OrderedDict([('det_acquisition_time',
              {'value': 0.0, 'timestamp': 1775030964.8847628})])