pcdsdevices.valve.VCN

class pcdsdevices.valve.VCN(prefix='', *, name, kind=None, read_attrs=None, configuration_attrs=None, parent=None, **kwargs)

VCN = Variable Controlled Needle valve

This is a valve that controls the amount of flow between two gas volumes, rather than cutting off or opening the flow entirely.

It corresponds to ST_VCN in the lcls-twincat-vacuum library.

Ophyd Device Components

Attribute	Class	Suffix	Docs	Kind	Notes
position_readback	EpicsSignalRO	:POS_RDBK_RBV	valve position readback	hinted
position_control	EpicsSignalWithRBV	:POS_REQ	requested positition to control the valve 0-100%	normal
upper_limit	EpicsSignalWithRBV	:Limit	max upper limit position to open the valve 0-100%	normal
interlock_ok	EpicsSignalRO	:ILK_OK_RBV	interlock ok status	normal
open_command	EpicsSignalWithRBV	:OPN_SW	Epics command to Open valve	normal
state	EpicsSignalWithRBV	:STATE	Valve state	hinted
pos_ao	EpicsSignalRO	:POS_AO_R_RBV		hinted

Methods

configure(d: Dict[str, Any]) → Tuple[Dict[str, Any], Dict[str, Any]]

Configure the device for something during a run

This default implementation allows the user to change any of the configuration_attrs. Subclasses might override this to perform additional input validation, cleanup, etc.

Parameters:

d (dict) – The configuration dictionary. To specify the order that the changes should be made, use an OrderedDict.

Returns:

• (old, new) tuple of dictionaries

• Where old and new are pre- and post-configure configuration states.

describe() → OrderedDictType[str, Dict[str, Any]]

Provide schema and meta-data for read().

This keys in the OrderedDict this method returns must match the keys in the OrderedDict return by read().

This provides schema related information, (ex shape, dtype), the source (ex PV name), and if available, units, limits, precision etc.

Returns:

data_keys (OrderedDict) – The keys must be strings and the values must be dict-like with the event_model.event_descriptor.data_key schema.

get(**kwargs)

Get the value of all components in the device

Keyword arguments are passed onto each signal.get(). Components beginning with an underscore will not be included.

read() → OrderedDictType[str, Dict[str, Any]]

Read data from the device.

This method is expected to be as instantaneous as possible, with any substantial acquisition time taken care of in trigger().

The OrderedDict returned by this method must have identical keys (in the same order) as the OrderedDict returned by describe().

By convention, the first key in the return is the ‘primary’ key and maybe used by heuristics in bluesky.

The values in the ordered dictionary must be dict (-likes) with the keys {'value', 'timestamp'}. The 'value' may have any type, the timestamp must be a float UNIX epoch timestamp in UTC.

Returns:

data (OrderedDict) – The keys must be strings and the values must be dict-like with the keys {'value', 'timestamp'}

read_configuration() → OrderedDictType[str, Dict[str, Any]]

Dictionary mapping names to value dicts with keys: value, timestamp

To control which fields are included, change the Component kinds on the device, or modify the configuration_attrs list.

stop(*, success=False)

Stop the Device and all (instantiated) subdevices

summary()

trigger() → StatusBase

Trigger the device and return status object.

This method is responsible for implementing ‘trigger’ or ‘acquire’ functionality of this device.

If there is an appreciable time between triggering the device and it being able to be read (via the read() method) then this method is also responsible for arranging that the StatusBase object returned by this method is notified when the device is ready to be read.

If there is no delay between triggering and being readable, then this method must return a StatusBase object which is already completed.

Returns:

status (StatusBase) – StatusBase object which will be marked as complete when the device is ready to be read.

Attributes

configuration_attrs

connected

hints

kind

subscriptions: ClassVar[FrozenSet[str]] = frozenset({'acq_done'})