Agilent OpenLab CDS (.dx) File Structure

A .dx file is an Agilent OpenLab CDS 2.x export. Unlike the older .D directory, it is a single Open Packaging Conventions (OPC) archive, which is an ordinary zip file. Its binary payloads share their encodings with the Chemstation formats, so rainbow reuses the existing decoders and only adds a thin layer to read the archive and recover the names that the payloads themselves do not carry.

The archive contains:

File	Information
injection.acmd	Manifest mapping each payload to its device, description, and units
`*.UV`	DAD spectrum (the `OL` variant of the .uv format)
`*.CH`	Single-wavelength signals (the `179` .ch format)
`*.IT`	Instrument telemetry (same `179` container as `*.CH`)
`[Content_Types].xml`, `_rels/`	OPC packaging metadata

Payload filenames are GUIDs, so the human-readable names and detector roles come from the manifest rather than the binaries.

injection.acmd is an XML manifest. Each Signal element maps a trace GUID (TraceId) to its DeviceName, Description, Units, and Encoding. The leading token of the description (e.g. DAD1A) is used as the trace name, and the encoding distinguishes detector signals from instrument telemetry. The InjectionInfo element provides the directory-level date, method, sample name, and vial position.

<Signal>
    <Encoding>Agilent.OpenLab.Rawdata/Spectra131</Encoding>
    <TraceId>7aa3654a-9e49-4a53-9acb-47d9731bbe50</TraceId>
    <DeviceName>DAD</DeviceName>
    <Description>DAD1I,DAD: Spectrum</Description>
    <Units>mAU</Units>
</Signal>

The .UV spectrum uses the same 131 / OL layout as the older .uv format (raw little-endian doubles), but the OpenLab values carry an additional 17-bit fixed-point shift. rainbow therefore scales parse_uv’s output by 2**-17 to recover the physical absorbance in mAU. This was confirmed against the .CH single-wavelength channels, which sample the same run and are already correctly scaled.

The .CH and .IT traces are single-channel 179 files, decoded by the existing .ch parser with no scaling change. The .CH files are extracted detector signals (e.g. a 210 nm chromatogram) and become UV DataFiles; the .IT files are instrument telemetry (pressure, temperature, flow, solvent ratios) and become analog data.

Note

Telemetry (.IT) is skipped by default, since most users only want the detector signals. Pass telemetry=True to include it as analog data:

import rainbow as rb
datadir = rb.read("path/to/data.dx", telemetry=True)
datadir.analog   # the instrument telemetry traces

A telemetry trace named explicitly in requested_files is always parsed, regardless of the flag.

The decoding of the OpenLab .dx format, and the test data used to validate it, were contributed by an anonymous collaborator.