Python API Reference¶

The Python API for Linux allows users to communicate and control a Measurement Computing WebDAQ logger using the Python language.

The API provides structures and enumerations to manage connected devices, obtain information about device capabilities, and configure hardware settings. Subsystem methods provide full-functionality for each device type.

Device Discovery¶

The API provides a method that gets a list of available WebDAQ devices connected to the system.

get_daq_device_inventory(interface_type, number_of_devices=100)¶

Gets a list of DaqDeviceDescriptor objects that can be used as the DaqDevice class parameter to create DaqDevice objects.

Parameters:	interface_type (InterfaceType) – One or more of the `InterfaceType` attributes (suitable for bit-wise operations) specifying which physical interfaces (such as USB) to search for devices. number_of_devices (Optional[int]) – Optional parameter indicating the maximum number of devices to return in the list; the default is 100).
Returns:	A list of `DaqDeviceDescriptor` objects that describe each of the each of the devices found on the specified interface.
Return type:	list[DaqDeviceDescriptor]
Raises:	`ULException`

Device Management¶

The API provides a class to manage devices connected to the system:

DaqDevice

DaqDevice class¶

Provides access to available MCC WebDAQ devices for operation, configuration, and retrieving information.

Methods¶

class DaqDevice(daq_device_descriptor)¶

Creates a DaqDevice object based on the daq_device_descriptor (usually obtained using get_daq_device_inventory()). The DaqDevice object allows access to all of the classes, methods, and attributes for the associated MCC device.

Parameters:	daq_device_descriptor (DaqDeviceDescriptor) – The object that describes the DAQ device.
Raises:	`ULException`

Method	Description
`get_descriptor()`	Returns the DaqDeviceDescriptor for an existing `DaqDevice` object.
`connect()`	Establishes a connection to a physical DAQ device referenced by the `DaqDevice` object.
`is_connected()`	Gets the connection status of a DAQ device referenced by the `DaqDevice` object.
`disconnect()`	Disconnects from the DAQ device referenced by the `DaqDevice` object.
`get_ai_device()`	Gets the analog input subsystem object used to access the AI subsystem for the device referenced by the `DaqDevice` object.
`release()`	Removes the device referenced by the `DaqDevice` object from the Universal Library, and releases all resources associated with that device.

get_descriptor()¶

Returns the DaqDeviceDescriptor for an existing DaqDevice object.

Returns:	The object that describes the DAQ device.
Return type:	DaqDeviceDescriptor
Raises:	`ULException`

connect()¶

Establish a connection to a physical DAQ device referenced by the DaqDevice object.

Raises:	`ULException`

is_connected()¶

Gets the DAQ device connection status for the device referenced by the DaqDevice object.

Returns:	True if the DAQ device is connected, otherwise False.
Return type:	bool
Raises:	`ULException`

disconnect()¶

Disconnects from the DAQ device referenced by the DaqDevice object.

Raises:	`ULException`

get_ai_device()¶

Gets the analog input subsystem object used to access the AI subsystem for the device referenced by the DaqDevice object.

Returns:	The object used to access the AI subsystem.
Return type:	AiDevice

release()¶

Removes the device referenced by the DaqDevice object from the Universal Library, and releases all resources associated with that device.

Raises:	`ULException`

Analog Input Subsystem¶

The API provides classes to manage the AI subsystem on a device:

AiDevice

AiConfig

AiDevice class¶

Analog input subsystem of the UL DAQ Device.

Methods¶

class AiDevice¶

An instance of the AiDevice class is obtained by calling DaqDevice.get_ai_device().

Method	Description
`get_config()`	Gets the analog input configuration object for the device referenced by the `AiDevice` object.
`a_in_scan()`	Scans a range of A/D channels on the device referenced by the `AiDevice` object, and stores the samples.
`a_in_load_queue()`	Loads the A/D queue of the device referenced by the `AiDevice` object.
`get_scan_status()`	Gets the status, count, and index of an A/D scan operation on the device referenced by the `AiDevice` object.
`scan_stop()`	Stops the analog input scan operation currently running on the device referenced by the `AiDevice` object.

get_config()¶

Gets the analog input configuration object for the device referenced by the AiDevice object.

Returns:	An object used for setting and retrieving the configuration settings for the analog input subsystem of the UL DAQ Device.
Return type:	AiConfig

a_in_scan(low_channel, high_channel, input_mode, analog_range, samples_per_channel, rate, options, flags, data)¶

Scans a range of A/D channels on the device referenced by the AiDevice object, and stores the samples.

Parameters:	low_channel (int) – First A/D channel in the scan. high_channel (int) – Last A/D channel in the scan. input_mode (AiInputMode) – The input mode of the specified channels. analog_range (Range) – The range of the data being read. samples_per_channel (int) – the number of A/D samples to collect from each channel in the scan. rate (float) – A/D sample rate in samples per channel per second. options (ScanOption) – One or more of the attributes (suitable for bit-wise operations) specifying the optional conditions that will be applied to the scan, such as continuous or external clock. flags (AInScanFlag) – One or more of the attributes (suitable for bit-wise operations) specifying the conditioning applied to the data before it is returned. data (Array[float]) – The buffer to receive the data. Use `create_float_buffer` to create the buffer.
Returns:	The actual input scan rate of the scan.
Return type:	float
Raises:	`ULException`

a_in_load_queue(queue)¶

Loads the A/D queue of the device referenced by the AiDevice object.

Parameters:	queue (list[AiQueueElement]) – A list of AiQueueElement structs, each of which contains fields specifying the channel, range, and mode.
Raises:	`ULException`

get_scan_status()¶

Gets the status, count, and index of an A/D scan operation on the device referenced by the AiDevice object.

Returns:	A namedtuple containing the scan status, total sample count, and current buffer index for the analog input background operation.
Return type:	ScanStatusInfo
Raises:	`ULException`

scan_stop()¶

Stops the analog input scan operation currently running on the device referenced by the AiDevice object.

Raises:	`ULException`

AiConfig class¶

Provides information about the configuration of the analog input subsystem.

Methods¶

class AiConfig¶

Provides information about the configuration of the analog input subsystem.

Parameters:	handle – UL DAQ Device handle.

Method	Description
`set_chan_type()`	Configures the channel type for the specified A/D channel.
`get_chan_type()`	Gets the channel type for the specified A/D channel.
`set_chan_tc_type()`	Configures the thermocouple type for the specified A/D channel.
`get_chan_tc_type()`	Gets the thermocouple type for the specified A/D channel.
`set_chan_temp_unit()`	Configures the temperature unit for the specified A/D channel.
`get_chan_temp_unit()`	Gets the temperature unit for the specified A/D channel.
`set_auto_zero_mode()`	Configures the auto zero mode for the analog input subsystem.
`get_auto_zero_mode()`	Gets the auto zero mode of the analog input subsystem.
`set_adc_timing_mode()`	Configures the A/D converter timing mode for the analog input subsystem.
`get_adc_timing_mode()`	Gets the A/D converter timing mode of the analog input subsystem.
`set_chan_iepe_mode()`	Configures the IEPE mode for the specified A/D channel.
`get_chan_iepe_mode()`	Gets the IEPE mode of the specified A/D channel.
`set_chan_coupling_mode()`	Configures the coupling mode for the specified A/D channel.
`get_chan_coupling_mode()`	Gets the coupling mode of the specified A/D channel.
`set_chan_sensor_sensitivity()`	Configures the sensor sensitivity of the specified A/D channel.
`get_chan_sensor_sensitivity()`	Gets the sensor sensitivity of the specified A/D channel.
`set_chan_slope()`	Configures the slope multiplier for the specified A/D channel.
`get_chan_slope()`	Gets the slope multiplier of the specified A/D channel.
`set_chan_offset()`	Configures the offset value for the specified A/D channel.
`get_chan_offset()`	Gets the offset value of the specified A/D channel.
`get_cal_date()`	Gets the calibration date for the DAQ device.

set_chan_type(channel, chan_type)¶

Configures the channel type for the specified A/D channel.

Parameters:	channel (int) – The A/D channel number. chan_type (AiChanType) – The channel type to be set.
Raises:	`ULException`

get_chan_type(channel)¶

Gets the channel type for the specified A/D channel.

Parameters:	channel (int) – The A/D channel number.
Returns:	The channel type of the specified channel.
Return type:	AiChanType
Raises:	`ULException`

set_chan_tc_type(channel, tc_type)¶

Configures the thermocouple type for the specified A/D channel.

Parameters:	channel (int) – The A/D channel number whose thermocouple type is being set. tc_type (TcType) – The thermocouple type to set`
Raises:	`ULException`

get_chan_tc_type(channel)¶

Gets the thermocouple type for the specified A/D channel.

Parameters:	channel (int) – The A/D channel number whose thermocouple type is being determined.
Returns:	The thermocouple type of the specified channel.
Return type:	TcType
Raises:	`ULException`

set_chan_temp_unit(channel, temp_unit)¶

Configures the temperature unit for the specified A/D channel.

Parameters:	channel (int) – The A/D channel number whose temperature unit is being set. temp_unit (TempUnit) – The temperature unit to set.
Raises:	`ULException`

get_chan_temp_unit(channel)¶

Get the temperature unit for the specified A/D channel.

Parameters:	channel (int) – The A/D channel number whose temperature unit is being determined.
Returns:	The temperature unit of the specified channel.
Return type:	TempUnit
Raises:	`ULException`

set_auto_zero_mode(mode)¶

Configures the auto zero mode for the analog input subsystem.

Parameters:	mode (AutoZeroMode) – The auto zero mode to set.
Raises:	`ULException`

get_auto_zero_mode()¶

Gets the auto zero mode of the analog input subsystem.

Returns:	The auto zero mode.
Return type:	AutoZeroMode
Raises:	`ULException`

set_adc_timing_mode(mode)¶

Configures the A/D converter timing mode for the analog input subsystem.

Parameters:	mode (AdcTimingMode) – The A/D converter timing mode.
Raises:	`ULException`

get_adc_timing_mode()¶

Gets the A/D converter timing mode of the analog input subsystem.

Returns:	The A/D converter timing mode.
Return type:	AdcTimingMode
Raises:	`ULException`

set_chan_iepe_mode(channel, mode)¶

Configures the IEPE mode for the specified A/D channel.

Parameters:	channel (int) – The A/D channel number whose IEPE mode is being set. mode (IepeMode) – The IEPE mode to set.
Raises:	`ULException`

get_chan_iepe_mode(channel)¶

Gets the IEPE mode of the specified A/D channel.

Parameters:	channel (int) – The A/D channel number whose IEPE mode is being determined.
Returns:	The IEPE mode of the specified channel.
Return type:	IepeMode
Raises:	`ULException`

set_chan_coupling_mode(channel, mode)¶

Configures the coupling mode for the specified A/D channel.

Parameters:	channel (int) – The A/D channel number whose coupling mode is being set. mode (CouplingMode) – The coupling mode to set.
Raises:	`ULException`

get_chan_coupling_mode(channel)¶

Gets the coupling mode of the specified A/D channel.

Parameters:	channel (int) – The A/D channel number whose coupling mode is being determined.
Returns:	The coupling mode of the specified channel.
Return type:	CouplingMode
Raises:	`ULException`

set_chan_sensor_sensitivity(channel, sensitivity)¶

Configures the sensor sensitivity for the specified A/D channel.

Parameters:	channel (int) – The A/D channel number whose sensor sensitivity is being set. sensitivity (float) – The sensor sensitivity to set in V/unit.
Raises:	`ULException`

get_chan_sensor_sensitivity(channel)¶

Gets the sensor sensitivity for the specified A/D channel.

Parameters:	channel (int) – The A/D channel number whose sensor sensitivity is being determined.
Returns:	The sensor sensitivity of the specified channel.
Return type:	float
Raises:	`ULException`

set_chan_slope(channel, slope)¶

Configures the slope multiplier for the specified A/D channel.

Parameters:	channel (int) – The A/D channel number whose slope is being set. slope (float) – The slope multiplier value to set.
Raises:	`ULException`

get_chan_slope(channel)¶

Gets the slope multiplier of the specified A/D channel.

Parameters:	channel (int) – The A/D channel number whose slope is being determined.
Returns:	The slope multiplier of the specified A/D channel.
Return type:	float
Raises:	`ULException`

set_chan_offset(channel, offset)¶

Sets the offset value for the specified A/D channel.

Parameters:	channel (int) – The A/D channel number whose offset is being set. offset (float) – The offset value to set.
Raises:	`ULException`

get_chan_offset(channel)¶

Gets the offset value of the specified A/D channel.

Parameters:	channel (int) – The A/D channel number whose offset is being determined.
Returns:	The offset of the specified A/D channel.
Return type:	float
Raises:	`ULException`

get_cal_date()¶

Gets the calibration date for the DAQ device.

Returns:	An integer containing the calibration date for the DAQ device in UNIX Epoch time.
Return type:	int
Raises:	`ULException`

Global Methods¶

Buffer Management¶

Provides a method to allocate buffers for data storage:

Method Description

create_float_buffer() Creates a buffer for double precision floating point sample values.

create_float_buffer(number_of_channels, samples_per_channel)¶

Create a buffer for double precision floating point sample values.

Parameters:	number_of_channels (int) – Number of channels in the scan. samples_per_channel (int) – Number samples per channel to be stored in the buffer.
Returns:	An array of size number_of_channels * samples_per_channel
Return type:	Array[float]

ULException class¶

Exception for an error in the UL.

exception ULException(error_code)¶

Exception for an error in the UL.

Parameters:	error_code (ULError) – A ULError error code value.

error_code = None¶: The ULError error code value.

error_message = None¶: The error message

Constants¶

AiChanType

AiInputMode

AInScanFlag

InterfaceType

Range

ScanOption

ScanStatus

TcType

TempUnit

ULError

class AiChanType¶

Contains attributes suitable for bit-wise operations describing channel types.

VOLTAGE = 1¶: Voltage

TC = 2¶: Thermocouple

RTD = 3¶: Resistance Temperature Detector (RTD)

THERMISTOR = 4¶: Thermistor

SEMICONDUCTOR = 5¶: Semiconductor

DISABLED = 100¶: Disabled

class AiInputMode¶

Contains attributes indicating A/D channel input modes. Used with most analog input methods and with many of the get_info methods.

DIFFERENTIAL = 1¶: Differential

SINGLE_ENDED = 2¶: Single-ended

PSEUDO_DIFFERENTIAL = 3¶: Pseudo-differential

class AInScanFlag¶

Contains attributes indicating conditioning to apply to analog input data before it’s returned.

DEFAULT = 0¶: User data should be in scaled format (usually volts). The data is then written to the device after converting to native device format and calibration factors (if any) applied.

NOSCALEDATA = 1¶: Data is returned in native format, without scaling applied.

NOCALIBRATEDATA = 2¶: Data is returned without calibration factors applied.

class InterfaceType¶

Contains attributes suitable for bit-wise operations indicating the physical connection interface used to communicate with a DAQ device. Values can be OR’d together to specify multiple interfaces.

USB = 1¶: USB interface

BLUETOOTH = 2¶: Bluetooth interface

ETHERNET = 4¶: Ethernet interface

ANY = 7¶: Any interface

class Range¶

Used with many analog input and output functions, as well as a return value for get_ranges().

BIP60VOLTS = 1¶: -60 to +60 Volts

BIP30VOLTS = 2¶: -30 to +30 Volts

BIP15VOLTS = 3¶: -15 to +15 Volts

BIP20VOLTS = 4¶: -20 to +20 Volts

BIP10VOLTS = 5¶: -10 to +10 Volts

BIP5VOLTS = 6¶: -5 to +5 Volts

BIP4VOLTS = 7¶: -4 to +4 Volts

BIP2PT5VOLTS = 8¶: -2.5 to +2.5 Volts

BIP2VOLTS = 9¶: -2.0 to +2.0 Volts

BIP1PT25VOLTS = 10¶: -1.25 to +1.25 Volts

BIP1VOLTS = 11¶: -1 to +1 Volts

BIPPT625VOLTS = 12¶: -.625 to +.625 Volts

BIPPT5VOLTS = 13¶: -.5 to +.5 Volts

BIPPT25VOLTS = 14¶: -0.25 to +0.25 Volts

BIPPT125VOLTS = 15¶: -0.125 to +0.125 Volts

BIPPT2VOLTS = 16¶: -0.2 to +0.2 Volts

BIPPT1VOLTS = 17¶: -.1 to +.1 Volts

BIPPT05VOLTS = 18¶: -.05 to +.05 Volts

BIPPT01VOLTS = 19¶: -.01 to +.01 Volts

BIPPT005VOLTS = 20¶: -.005 to +.005 Volts

BIP1PT67VOLTS = 21¶: -1.67 to +1.67 Volts

BIPPT312VOLTS = 22¶: -0.312 to +0.312 Volts

BIPPT156VOLTS = 23¶: -0.156 to +0.156 Volts

BIPPT078VOLTS = 24¶: -0.078 to +0.078 Volts

class ScanOption¶

Contains attributes suitable for bit-wise operations indicating optional scan modes. These values can be OR’d together to specify multiple options.

DEFAULTIO = 0¶: Transfers A/D data based on the board type and sampling speed.

SINGLEIO = 1¶: Transfers one packet of data at a time.

BLOCKIO = 2¶: Transfers A/D data in blocks.

BURSTIO = 4¶: Transfers A/D data from the FIFO after the scan completes. Allows maximum rates for finite scans up to the full capacity of the FIFO. Not recommended for slow acquisition rates.

CONTINUOUS = 8¶: Scans data in an endless loop. The only way to stop the operation is with scan_stop().

EXTCLOCK = 16¶: Data conversions are controlled by an external clock signal.

EXTTRIGGER = 32¶: Sampling begins when a trigger condition is met.

RETRIGGER = 64¶: Re-arms the trigger after a trigger event is performed.

BURSTMODE = 128¶: Enables burst mode sampling, minimizing the channel skew.

class ScanStatus¶

Scan status.

IDLE = 0¶: The scan is idle.

RUNNING = 1¶: The scan is running.

class TcType¶

Contains attributes for thermocouple types.

J = 1¶: Type J

K = 2¶: Type K

T = 3¶: Type T

E = 4¶: Type E

R = 5¶: Type R

S = 6¶: Type S

B = 7¶: Type B

N = 8¶: Type N

class TempUnit¶

Contains attributes for temperature units.

CELSIUS = 1¶: Celsius

FAHRENHEIT = 2¶: Fahrenheit

KELVIN = 3¶: Kelvin

class ULError¶

Error codes for Universal Library.

NO_ERROR = 0¶: No error has occurred

UNHANDLED_EXCEPTION = 1¶: Unhandled internal exception

BAD_DEV_HANDLE = 2¶: Invalid device handle

BAD_DEV_TYPE = 3¶: This function cannot be used with this device

USB_INTERFACE_CLAIMED = 4¶: USB interface is already claimed

DEV_NOT_FOUND = 5¶: Device not found

DEV_NOT_CONNECTED = 6¶: Device not connected or connection lost

DEAD_DEV = 7¶: Device no longer responding

BAD_BUFFER_SIZE = 8¶: Buffer too small for operation

BAD_BUFFER = 9¶: Invalid buffer

BAD_MEM_TYPE = 10¶: Invalid memory type

BAD_MEM_REGION = 11¶: Invalid memory region

BAD_RANGE = 12¶: Invalid range

BAD_AI_CHAN = 13¶: Invalid analog input channel specified

BAD_INPUT_MODE = 14¶: Invalid input mode specified

ALREADY_ACTIVE = 15¶: A background process is already in progress

BAD_TRIG_TYPE = 16¶: Invalid trigger type specified

OVERRUN = 17¶: FIFO overrun, data was not transferred from device fast enough

UNDERRUN = 18¶: FIFO underrun, data was not transferred to device fast enough

TIMEDOUT = 19¶: Operation timed out

BAD_OPTION = 20¶: Invalid option specified

BAD_RATE = 21¶: Invalid sampling rate specified

BAD_BURSTIO_COUNT = 22¶: Sample count cannot be greater than FIFO size for BURSTIO scans

CONFIG_NOT_SUPPORTED = 23¶: Configuration not supported

BAD_CONFIG_VAL = 24¶: Invalid configuration value

BAD_AI_CHAN_TYPE = 25¶: Invalid analog input channel type specified

ADC_OVERRUN = 26¶: ADC overrun occurred

BAD_TC_TYPE = None¶: Invalid thermocouple type specified

BAD_UNIT = 27¶: Invalid unit specified

BAD_QUEUE_SIZE = 29¶: Invalid queue size

BAD_CONFIG_ITEM = 30¶: Invalid config item specified

BAD_INFO_ITEM = 31¶: Invalid info item specified

BAD_FLAG = 32¶: Invalid flag specified

BAD_SAMPLE_COUNT = 33¶: Invalid sample count specified

INTERNAL = 34¶: Internal error

BAD_COUPLING_MODE = 35¶: Invalid coupling mode

BAD_SENSOR_SENSITIVITY = 36¶: Invalid sensor sensitivity

BAD_IEPE_MODE = 37¶: Invalid IEPE mode

BAD_AI_CHAN_QUEUE = 38¶: Invalid channel queue specified

BAD_AI_GAIN_QUEUE = 39¶: Invalid gain queue specified

Types¶

DaqDeviceDescriptor

AiQueueElement

class DaqDeviceDescriptor¶

A class containing properties that define a particular DAQ device.

product_name¶: The generic (unqualified) product name of the device referenced by the DaqDeviceDescriptor.

product_id¶: The numeric string indicating the product type referenced by the DaqDeviceDescriptor.

dev_interface¶: The InterfaceType indicating the type of interface in use by the device referenced by the DaqDeviceDescriptor.

dev_string¶: Similar to product_name, but may contain additional information.

unique_id¶: A string that uniquely identifies a specific device, usually with a serial number or MAC address.

class AiQueueElement¶

A class containing properties that define an analog input queue element.

channel¶: The analog input channel number for the queue element.

input_mode¶: The AiInputMode value to use for the specified channel for the queue element.

range¶: The Range value to use for the specified channel for the queue element.