:JSAMemory:JSANalysis:SPECtrum:FLOat:YDATa?

Query Syntax

:JSAMemory:JSANalysis:SPECtrum:FLOat:YDATa?

Description

Returns the amplitude (Y-axis) data points as 32-bit floating-point values. The returned amplitude values are in volts or Watts and do not require scaling. The data returned from this query has high resolution but can require long tranfer times for long patterns. If fast transfer time is more important than measurement resolution, use the :JSAMemory:JSANalysis:SPECtrum:ASCii:YDATa? query instead. Use the :WAVeform:SOURce? query to select data from a channel, differential channel, waveform memory, or a function.

The data is sent starting from the lowest and progressing to the highest frequency. The frequency at any data point can be calculated as:

Frequency = (data point)(frequency spacing) + f_origin

where,

• frequency spacing is the frequency difference between adjacent data points and is returned with the :JSAMemory:JSANalysis:SPECtrum:XINCrement? query.
• data point is integer ranging from 0 to the number of waveform points minus one. Use the :JSAMemory:JSANalysis:SPECtrum:POINts? query to return the number of points in the waveform.
• f_origin is the frequency at the first data point and is returned using the :JSAMemory:JSANalysis:SPECtrum:XORigin? query.

Returned Data Type

The :JSAMemory:JSANalysis:SPECtrum:FLOat:YDATa? query returns float (4 bytes) values as binary definite-length block data queries binary definite-length block data queries binary definite-length block data queries. You must specify this data type in your program language's command that you use to query the data. The specifier for this data type in your programming language will likely be "f" and it is identified in this example with red text. Confirm this with your programming language's documentation. The following is an example of the command used in Python using pyvisa.

Flex.read_termination = ''
Flex.write_termination = ''
endianness = Flex.query(':SYSTem:BORDER?')
Flex.write(':SYSTem:BORDER LENDian')
data = Flex.query_binary_values(':JSAMemory:JSANalysis:SPECtrum:FLOat:YDATa?',
	datatype='f',
	container=list,
	is_big_endian=False,
	header_fmt='ieee')
Flex.write(':SYSTem:BORDER ' + endianness)

Endianness of Returned Definite-Length Block Data

To correctly interpret definite-length block data, you must know the endianness (byte order) of the returned data (integers or real) from FlexDCA and you will must likely need specify this same endianness in your program language's command that is used to query the data. Endianness can be set to "little endian" order in which the least significant byte is sent first and the most significant byte sent last. Or, the endianness can be set to "big endian" order in which the most significant byte is sent first and the least significant byte sent last.

To specify or query the endianness setting for binary block data, use the :SYSTem:BORDer command. The endiannes setting applies to all binary queries except for :DISK:FILE:READ? query.

If you plan to change FlexDCA's current endian setting, it is a good practice to query FlexDCA's current endian setting and restore the setting when your program completes. This will avoid other programs having errors due to assuming a particular endianness setting.

After a factory preset (:SYSTem:FACTory), sets little endian. A default setup (:SYSTem:DEFault) does not affect endianness.