BUCHI NIRCal

Status: Supported (scoped) · Vendor: BUCHI / Bühler · Extensions: .nir

NIRCal is the project file written by BUCHI/Bühler NIRCal software for FT-NIR calibration work. A .nir project bundles many sample spectra, a shared wavenumber axis, per-sample property values and per-spectrum acquisition metadata. nirs4all-formats reads the project file emitting one SpectralRecord per sample.

Instruments & software

Produced by BUCHI NIRCal software (NIRMaster / NIRFlex instrument families). The committed fixture is the prospectr::read_nircal() reference file; a richer local-only cannabis transfer file exercises non-null property targets and replicate spectra.

File structure

A text-keyed container that starts with NIRCAL Project File. Sections are located by ASCII markers rather than fixed offsets: the Spectra selection block holds sample identifiers, a Wavelength Selection block holds the wavenumber axis, a Properties section holds property names and per-sample property blocks, and a Spectra Info block holds per-spectrum metadata. Each spectrum is one double64 array delimited by fixed-size begin / end markers; the axis is emitted as wavenumber in cm-1. The token layout follows the observed NIRCal 2.23 ordering.

What nirs4all-formats extracts

  • Signals — one absorbance SpectralRecord per sample; the sample id is stored in metadata. Duplicate sample ids remain distinguishable through promoted replicate counters.

  • Axis — the shared wavenumber axis (cm-1), validated to match the declared spectrum length.

  • Targets — property names and per-sample values become targets. When every value in the property table is zero, those values are exposed as null to match prospectr::read_nircal() missing-value semantics; in mixed tables, a real 0.0 is preserved. Duplicate property names are normalised with a warning.

  • Metadata — project GUID, project-file version, project title, replicate index/count and per-spectrum Spectra Info fields promoted as flat snake_case: spectrum GUID, comment/description, scans, resolution, declared wavenumber geometry, device, instrument serials, software/instrument version, measurement cell, option serial, reference substance, creator/modifier (with logins), timestamps, computer name, and gain / instrument-temperature / sample-temperature diagnostics when present.

  • Provenance & warnings — buchi_nircal_reverse_engineered_sections plus any target / duplicate-name warnings, source file and SHA-256.

Variants & support status

Variant

Status

Notes

.nir project (spectra + axis + properties)

Supported

One record per sample; targets, replicates and spectrum metadata.

.nir with non-zero property targets

Supported (local-only)

Validated on a local cannabis transfer file; needs a redistributable fixture.

.cal calibration-only

Planned

Not yet parsed.

JCAMP-DX export

Planned

Routed to the JCAMP reader once fixtures exist.

NIRMaster / NIRFlex firmware variants

Planned

Spectra Info parser follows NIRCal 2.23; new firmware needs comparison against vendor exports.

Limitations & known gaps

  • Non-zero reference properties are validated only locally; a small redistributable fixture is still needed before the target path is claimed publicly.

  • Calibration-only .cal files, JCAMP-DX exports and broader NIRMaster / NIRFlex firmware variants are not yet handled.

  • The Spectra Info parser tracks the observed NIRCal 2.23 token layout, so new firmware fixtures should be compared against vendor exports or prospectr before the compatibility claim is widened.

Reference readers

prospectr::read_nircal() (R) is the naming and missing-value reference for this format.

Samples & validation

samples/buchi_nircal/muestras-tejido-foliar_transfer.nir (20 records, cm-1, 1501 points, absorbance; 20 property targets present but null) is golden-backed and validates spectrum GUID, device/serial, scans/resolution and gain/temperature metadata. The local-only transpec_DEMO_cannabis.nir (105 records, 3 replicate spectra per sample) validates the non-null CBDA / THCA target path plus the replicate, comment/timestamp and device/serial metadata. NIRCal .nir is distinguished from Foss/WinISI .NIR by the NIRCAL Project File header, never by extension.