Calibrations – Radiometric and Wavelength

Ocean Insight’s spectrometer calibration is considered stable over time because the spectrometer has no moving parts. However, anything that affects the physical dimension of the bench can have an effect on calibration, including infrequent, accidental occurrences like dropping the spectrometer. Also, as the initial calibrations are performed at room temperature; any significant departures from room temperature will change the wavelength calibration. Spectrometers are exposed to changes in temperature and other conditions that can affect performance. Regular spectrometer wavelength calibration is recommended to correct for drift and similar phenomena inherent to all spectrometers.

Most Ocean Insight spectrometers have field-replaceable entrance slits. If in order to optimize spectrometer performance the slit size has been changed or a filter was added, the spectrometer must be recalibrated because the filter changes the optical focus and wavelength calibration of the spectrometer. (Slit-with-filter changes must be performed at Ocean Insight.) Also, recalibration is necessary when changing from a larger slit to a smaller slit. But recalibration is optional when changing from a smaller slit to a larger one, although it is still recommended that a calibration be performed to ensure best performance.

Ocean Insight offers in-house spectroradiometric and wavelengths calibrations. Calibrations can be certificated or performed according to an ISO standard at an additional fee.

Alternatively, Ocean Insight supplies a variety of calibrated light sources for do-it-yourself wavelength calibrations.

In-house Radiometric Calibrations

Ocean Insight performs spectroradiometric calibrations using a NIST-traceable light source for which irradiance as a function of distance is known. This allows to calibrate systems for a range of sampling optics, across different wavelength ranges, and at both high and low light intensities. Setups are radiometrically calibrated as complete systems, so care must be taken during use to avoid damage to or stress on each component to maintain the accuracy of the calibration. Also, disturbing the setup after calibration – for example, unscrewing a fiber — will invalidate the calibration.

If the accuracy of the radiometric performance is crucial for the application, a wavelength calibration must still be performed. This is a standard practice for all radiometric calibrations that Ocean Insight performs in its ISO/IEC 17025:2017-certified lab.

Service Code Spectral range, nm ISO accredited
SPEC-CAL 350-1700 No
SPEC-CAL-ISO 350-1600 17025
SPEC-CAL-NIR 900-2500 No
SPEC-CAL-UV 200-1050 No
SPEC-CAL-UV-EXT 210-1100 No

In-house Wavelength Calibrations

Ocean Insight performs an in-house calibration which is referred to as a WAVECAL and is processed as an RMA (return authorization request).

The calibration costs are spectrometer specific and an additional WAVECAL-CERT certification service is offered at a nominal fee.

Wavelength Calibration Light Sources

Wavelength Calibration Light Source

A more convenient option  – especially if you need to recalibrate often – is to invest in a spectrometer wavelength calibration source and perform the calibration in the lab or field.

The How to Perform Wavelength Calibrations on a Modular Spectrometer Quick Start Guide (https://www.oceaninsight.com/globalassets/catalog-blocks-and-images/manual–instruction-re-branded/mnl-1015-wavelength-calibration-qsg-rev-a.pdf) will walk you through the process.

Every spectrometer includes a sheet listing its wavelength calibration coefficients (four floating-point values that can be used to derive the wavelength associated with each pixel on the detector), as well as a summary of the spectral lines (from mercury, argon, xenon, neon and other calibrated line sources) used to generate those coefficients.

To complement that information, an EEPROM flash memory chip in each spectrometer contains wavelength calibration coefficients, linearity coefficients, and a serial number unique to each spectrometer. The spectroscopy application reads these values directly from the spectrometer, enabling the ability to “hot-swap” spectrometers between computers without entering the spectrometer coefficients manually on each computer.

Calibration Light Source Emission source Spectral range, nm
AR-2 Argon 696-1704
HG-2 Mercury-Argon 253-923
KR-2 Krypton 427-893
NE-2 Neon 540-754
XE-2 Xenon 916-1984

Radiometric Calibration Light Sources

Radiometric Calibration Light Source

Radiometrically calibrated light sources from Ocean Insight are used to calibrate the absolute spectral response of a spectrometer system. Using these light sources and our software, one can determine absolute intensity values across UV, Visible and NIR wavelengths.

An extended-range (to 2400 nm) calibration option is also available, for an additional fee.

Radiometrically calibrated light sources are carefully characterized to deliver a known quantity of light with very low uncertainty. Each source is measured to NIST-traceable standards, creating an unbroken chain of traceability.

Calibration Light Source Light source Spectral range, nm
DH-3P-CAL Deuterium & Tungsten Halogen 210-1100
DH-3P-BAL-CAL Deuterium & Tungsten Halogen 230-1100
HL-3P-CAL Tungsten Halogen 350-1100