Experimental Physics and
Industrial Control System

Gabriel de Souza Fedel <[email protected]> · Wed, 9 May 2018 16:29:12 -0300

Hi Mark,

On 09-05-2018 09:46, Mark Rivers wrote:

Hi Gabriel,

Is it possible to generate nexus files using areadetector for instance (with more than one "source", including waveform) ?

Nexus files can be generated in areaDetector either with the NDFileHDF5 plugin (recommended) or the Nexus plugin (soon to be deprecated).

The HDF5 plugin stores the data for one or more NDArrays, including all of the NDAttributes attached to those arrays.  NDAttributes are limited to scalar values of any data type (signed/unsigned 8/16/32-bit integers, 32/64 bit float, and strings).  NDAttributes cannot be arrays (waveforms).

Hum, I understand! thank you

I saw some nexus examples and now I understand them use nexus generated

by area detector (with a external link).

So it is not currently possible to do what you are asking with the NDFileHDF5 plugin, i.e. store arrays of different sizes from different sources in the same HDF5 file.

In the future it would be possible to extend NDAttributes to handle arrays, and it is has certainly been considered in the past.  The question is the scope: do we support just 1-D waveforms, or N-dimensional arrays?  If N-dimensional then should such arrays be NDArrays, and can they themselves have attributes?  That would become a complex project.

You are right, it is not a simple project.

I think I will continue my solution using python.

Thank you for the answers.

Regards

Mark

________________________________
From: [email protected] <[email protected]> on behalf of Gabriel de Souza Fedel <[email protected]>
Sent: Wednesday, May 9, 2018 6:56 AM
To: [email protected]
Subject: How do you generate nexus files?

Hi,

Here at Brazilian Synchrotron (LNLS) we are working to implement nexus
on some beamlines. We are working with python, getting all data from
epics PVs and build nexus files. On all the cases the most important
data are waveforms.

We would like to analyses other possibilities, and to verify how other
synchrotrons generate nexus files:

Do you are working with nexus files?
How do you generate them?
Are you using some high level language for it (like python, c++) ?
Is it possible to generate nexus files using areadetector for instance
(with more than one "source", including waveform) ?

Thank you.

Regards

--
Gabriel Fedel
Software de Operação das Linhas de Luz
Laboratório Nacional de Luz Síncrotron - (LNLS)
Centro Nacional de Pesquisa em Energia e Materiais (CNPEM)
[email protected] | +55 (19) 3512 1226
www.lnls.cnpem.br<http://www.lnls.cnpem.br>

--
Gabriel Fedel
Software de Operação das Linhas de Luz
Laboratório Nacional de Luz Síncrotron – (LNLS)
Centro Nacional de Pesquisa em Energia e Materiais (CNPEM)
[email protected] | +55 (19) 3512 1226
www.lnls.cnpem.br

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System