NIST Traceable VS NIST Compatible

NIST Traceable VS NIST Compatible

Some vendors of neutral density (ND) filters state that their filters are NIST Traceable. A researcher must ask themselves an important question: What does NIST Traceable really mean?  Many scientists get a warm and fuzzy feeling when they see spectrophotometer calibration standards that are "NIST Traceable."  The truth is NIST Traceability is not what people think it is.

Many people are fooled by this term.  NIST Traceable may not be sufficient for the appropriate calibration of a spectrophotometer.  Neutral density filters that are NIST compatible are what is truly required for the most accurate calibration.  The difference between "NIST Traceable" and "NIST Compatible" is as follows:

What is NIST Traceable?

NIST Traceable Neutral Density (ND) Filters means that the manufacturer of the ND filters placed them in a spectrophotometer, made a scan (aka. TRACE), and have a record of this scan on the optical density of these filters at different wavelengths of light.  The problem with this method is it does not give or guarantee any information on the tolerances of the ND filters including their temperature, humidity conditions, and other environmental stability, as well as incident light-angle sensitivity, optical density variation, wavelengths deviation, and all other parameters which must be followed in accordance with NIST.

This "Trace" scan that the spectrophotometer makes with any neutral density filter may or may not correspond with NIST performance requirements, because having a Trace is only one requirement according to NIST standards.

In short, any ND filter, whether it corresponds or does not correspond to all NIST requirements, which has the trace explained above is called NIST Traceable.  Again the filter tolerances that are traceable have varying tolerances and some may fall outside of NIST requirements.  This gives the term "NIST Traceable" little meaning.

What is NIST Compatible?

NIST Compatible Neutral Density (ND) filters mean that a manufacturer entirely followed all the procedures prescribed by NIST in order to manufacture and verify performance of the ND filters and create the corresponding traces for each manufactured ND filter.  Therefore, only NIST Compatible ND filters are truly accurate and must be used for the appropriate verification of performance and calibration of spectrophotometers in accordance with Good Laboratory Practices (GLP).

Spectrophotometer Calibration Kits manufactured by Precision Cells are one of the rare calibration kits on the market today that are NIST Compatible.  PC's kits exceed NIST Traceability guidelines and are quickly replacing old, outdated liquid kits.

Tolerances of PC's neutral density filters, as well as all other parameters to light, entirely correspond to NIST requirements.  PC's spectrophotometer calibration filters are not subject to high sensitivity to ambient temperatures and other various parameters that liquid filters are subject to.  And most importantly, performance of PC's calibration filters does not degrade over time, which is the biggest problem of all liquid based calibration standards.  This gives the PC spectrophotometer calibration standards multiple unique advantages over liquid based filters.

Precision Cells is quickly becoming the world leader in spectrophotometer calibration.  If scientists, researchers, and spectrophotometer manufacturers are interested in getting the best possible calibration results every time, then having one of PC's spectrophotometer calibration kits is mandatory.