pcdsdevices.pim.PPMPowerMeter

class pcdsdevices.pim.PPMPowerMeter(*args, **kwargs)

Analog measurement tool for beam energy as part of the PPM assembly.

When inserted into the beam, the raw_voltage signal value should increase proportional to the beam energy. The equivalent calibrated readings are dimensionless, which is a unitless number that represents the relative calibration of every power meter, and calibrated_mj, which is the real engineering unit of the beam power. These are calibrated using the other signals in the following way:

dimensionless = (raw_voltage + calib_offset) * calib_ratio calibrated_mj = dimensionless * calib_mj_ratio

Ophyd Device Components

Attribute	Class	Suffix	Docs	Kind	Notes
raw_voltage	PytmcSignal	:VOLT	Raw readback from the power meter.	normal
dimensionless	PytmcSignal	:CALIB	Calibrated dimensionless readback for cross-meter comparisons.	normal
calibrated_mj	PytmcSignal	:MJ	Calibrated absolute measurement of beam power in physics units.	normal
thermocouple	TwinCATThermocouple		Thermocouple on the power meter holder.	normal
calib_offset	PytmcSignal	:CALIB:OFFSET	Calibration parameter to offset raw voltage to zero for the calibrated quantities. Unique per power meter.	config
calib_ratio	PytmcSignal	:CALIB:RATIO	Calibration multiplier to convert to the dimensionless constant. Unique per power meter.	config
calib_mj_ratio	PytmcSignal	:CALIB:MJ_RATIO	Calibration multiplier to convert from the dimensionless constant to calibrated scientific quantity. Same for every power meter.	config
raw_voltage_buffer	PytmcSignal	:VOLT_BUFFER	Array of the last 1000 raw measurements. Polls faster than the EPICS updates.	omitted
dimensionless_buffer	PytmcSignal	:CALIB_BUFFER	Array of the last 1000 dimensionless measurements. Polls faster than the EPICS updates.	omitted
calibrated_mj_buffer	PytmcSignal	:MJ_BUFFER	Array of the last 1000 fully calibrated measurements. Polls faster than the EPICS updates.	omitted

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() → ophyd.device.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() → ophyd.device.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() → ophyd.device.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.

status() → str

Returns a str with the current pv values for the device.

stop(*, success=False)

Stop the Device and all (instantiated) subdevices

summary()

trigger() → ophyd.status.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