External Data Logging (ELOG)

The ELOG subsystem allows the SCPI user to retrieve synchronized access to multiple channels via statistics calculations.

First, the subsystem needs to be configured. Possible parameters are a channel list, aggregation calculations, aggregation duration as well as result formats and timestamp formats.

After configuration, the user can start the computations and fetch all values. By continuously requesting data records, gap-less readout is possible. Data is kept available inside Oxygen for at least 20 seconds before fetching of old samples is no longer possible.

ELOG cannot be configured during recording or armed triggers state.

:ELOG:ITEMs <channel>[,<channel>[,…]]

Syntax	:ELOG:ITEMs <channel> [,<channel> [,…]]
Description	Defines the ordered list of requested channels
Parameter	Name Type Range Default <channel> ASCII String Oxygen Channel Name None
Explanation	The user can specify a list of multiple scalar channels. The channels need not share the same sample-rate or raw numeric format. If a channel is not compatible, an error is generated, and the channel is not added to the list. If one of the registered channels becomes unused or is changed, the whole dataset will be discarded and the ELOG system will be in an error state. Use :ELOG:STATe? to get more details. The following channel types are supported: Analog, Counter, Math, Statistics, Filter, Power, AI Async Pad, CAN Signals, GPS-Position/Velocity/Heading/SecondsOfDay/Distance and Acceleration. For proper operation, a minimum sample rate of 5Hz is suggested.
Example	-> :ELOG:ITEMs "U1_tRMS@PowerGroup","AI 1/2"

:ELOG:ITEMs?

Syntax	:ELOG:ITEMs?
Description	Returns the current list of requested channels
Parameter	None
Explanation
Return Format	<ASCCI String>[, <ASCII String>[, …]] | NONE
Example	-> :ELOG:ITEMs? <- "U1_tRMS@PowerGroup","AI 1/2"

:ELOG:PERiod <Duration>

Syntax	:ELOG:PERiod <Duration>
Description	Sets the duration (in seconds) of the data aggregation time of statistics from source channels
Parameter	Name Type Range Default <duration> NRf > 0 0.1 seconds
Explanation	The duration period is the number of seconds where statistics values such as MIN/AVG/… are collected from the source channels (ITEMS). The minimum duration is limited by the frequency of the source channel. Values below the inverse of the source channel frequency will lead to an error state
Example	Set 2.5Hz (0.4) or 1kHz (0.001) minimum source channel frequency -> :ELOG:PERiod 0.4 ... -> :ELOG:PERiod 0.001

:ELOG:PERiod?

Syntax	:ELOG:PERiod?
Description	Queries the numeric data aggregation time for output (in seconds)
Parameter	None
Explanation
Return Format	<NR2>
Example	-> :ELOG:PER 0.5 -> :ELOG:PER? <- 0.5

:ELOG:CALCulations {AVG|MIN|MAX|RMS}

Syntax	:ELOG:CALCulations {AVG|MIN|MAX|RMS}[,{AVG|MIN|MAX|RMS}[,…]]
Description	Sets a list of requested statistical calculations for all channels
Parameter	Name Type Range Default Modes ASCII literal(s) AVG Average values MIN Minimum values MAX Maximum values RMS root-mean-square values AVG
Explanation	One or multiple calculations are performed for each ITEMS channel. When fetching data, calculations are returned in the same order as requested in CALC.
Example	-> :ELOG:CALCulations AVG,MAX,RMS

:ELOG:CALCulations?

:ELOG:PERiod?

Syntax	:ELOG:PERiod?
Description	Queries the list of configured calculation modes
Parameter	None
Explanation
Return Format	{AVG|MIN|MAX|RMS}[,{AVG|MIN|MAX|RMS}[,…]]
Example	-> :ELOG:CALC MIN,MAX -> :ELOG:CALC? <- MIN,MAX

:ELOG:FORMat {ASCII|BIN_INTEL|BIN_MOTOROLA}

Syntax	:ELOG:FORMat {ASCII|BIN_INTEL|BIN_MOTOROLA}
Description	Sets the requested output format
Parameter	Name Type Range Default Format ASCII literal(s) ASCII BIN_INTEL BIN_MOTOROLA ASCII
Explanation	When format is set to ASCII, all numbers are returned in the NR3 format (timestamps in NR2 format) When format is set to BIN_INTEL or BIN_MOTOROLA, all values are returned in IEEE 754 float32 formats (in the corresponding byte order). See FETCH for more details about record layouts
Example	-> :ELOG:FORM BIN_INTEL

:ELOG:FORMat?

Syntax	:ELOG:FORMat?
Description	Queries the list of configured calculation modes
Parameter	None
Explanation	Returns the currently configured output format
Return Format	{ASCII|BIN_INTEL|BIN_MOTOROLA}
Example	-> :ELOG:FORM? -> :ELOG:FORM? <- ASCII

:ELOG:TIMestamp {OFF|REL|ABS|ELOG}

Syntax	:ELOG:TIMestamp {OFF|REL|ABS|ELOG}
Description	Sets the requested timestamp format
Parameter	Name Type Range Default Mode ASCII literal(s) OFF No timestamp REL Seconds since acquisition start ABS Absolute timestamp as ISO date/time ELOG Seconds since the current ELOG session was started ASCII
Explanation	Enables or disables timestamp reporting when requesting data through FETCH. Relative times (REL) are reported as seconds since acquisition start, ELOG times are seconds since the first sample from the current ELOG session (after calling :ELOG:STARt). Absolute times are only reported in ASCII output format and have the following format: YYYY-MM-DDThh:mm:ss.xxxxxx
Example	-> :ELOG:TIM REL

:ELOG:TIMestamp?

Syntax	:ELOG:TIMestamp?
Description	Queries the currently configured timestamp format
Parameter	None
Explanation
Return Format	{OFF|REL|ABS|ELOG}
Example	-> :ELOG:TIM REL -> :ELOG:TIM? <- REL

:ELOG:STARt

Syntax	:ELOG:STARt
Description	Initializes and starts ELOG data gathering. Samples values can be fetched as early as one aggregation period after STARt. After calling STARt, no ELOG configuration is possible.
Parameter	None
Explanation
Example	-> :ELOG:STARt

:ELOG:FETCh? [<NUM>]

Syntax	:ELOG:FETCh [<max_records>]
Description	Fetches MAX_RECORDS records or less from the internal ELOG buffer. If no parameter is given, all available records are returned. FETCh is only possible after STARt.
Parameter	Name Type Range Default Max_records NR1 1 .. MAX MAX
Explanation	Fetch returns values at record level granularity. There is one record for each timestamp. Each record consists of values from all channels (ITEMs) and all calculation modes (CALC). If no data is available, NONE is returned. ERROR indicates an error. In ASCII mode, the result is a list of NRf values, all values of one record are returned consecutively, possibly prepended by the timestamp value (see example). In binary mode, for every channel-calculation, a separate Arbitrary Block with up to MAX_RECORDS float32 values is returned. When using timestamps, an Arbitrary Block with float32 timestamp values is returned as the first result. In the following examples, we assume the following settings, which configure a record of four values: -> :ELOG:ITEMs "CH0", "CH1" -> :ELOG:CALC AVG, MIN
Example	Timestamp CH0.AVG CH0.MIN CH1.AVG CH1.MIN 0.1 1.5 1 10.5 10 0.2 2.5 2 20.5 20 -> :ELOG:FORM ASCII; :ELOG:TIM OFF; :ELOG:STARt -> :ELOG:FETCh? 2 <- 1.5, 1, 10.5, 10, 2.5, 2, 20.5, 20 -> :ELOG:STOP ... -> :ELOG:FORM ASCII; :ELOG:TIM REL; :ELOG:STARt -> :ELOG:FETCh? 2 <- 0.1, 1.5, 1, 10.5, 10, 0.2, 2.5, 2, 20.5, 20 -> :ELOG:STOP ... -> :ELOG:FORM BIN_INTEL; :ELOG:TIM REL; :ELOG:STARt -> :ELOG:FETCh? 2 <- {0.1, 0.2}, {1.5, 2.5}, {1, 2}, {10.5, 20.5}, {10, 20} -> :ELOG:STOP

:ELOG:STOP

Syntax	:ELOG:STOP
Description	Stops buffering data after a previous STARt call, clears the data buffer and disables fetching.
Parameter	None
Explanation	The configuration is not changed; therefore, data acquisition can be restarted by calling STARt again.
Example	-> :ELOG:STOP

:ELOG:RESet

Syntax	:ELOG:RESet
Description	Resets the ELOG configuration and stops fetching if started with STARt. All parameters are set to their default values and the channel list (ITEMs) is cleared.
Parameter	None
Explanation	Same behavior as when calling *RST, but limited to the ELOG subsystem.
Example	-> :ELOG:RESet

:ELOG:STATe?

Syntax	:ELOG:STATe?
Description	Returns the internal state of the ELOG subsystem. This command is not needed for regular operations but is useful for information purposes. Possible states are: CONFIG, RUNNING and INVALID
Parameter	None
Explanation	The ELOG subsystem uses states internally. Initially, ELOG is in configuration state (CONFIG) which accepts commands like ITEMs, PER, CALC, FORM and TIM. After calling STARt, the subsystem is switched into a data gathering state (RUNNING) which no longer allows to modify the configuration. The configuration state can be entered again by either calling STOP or RESet. While fetching data from Oxygen through ELOG, the measurement configuration in Oxygen must not be changed. If a change of the configuration is detected, ELOG will stop fetching data and an error is reported when calling FETCh. The state query will return the INVALID state in this case
Return Format	ASCII literal
Example	-> :ELOG:STATe? <- RUNNING