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Calibration Glossary
1-Point Calibration–
a.k.a. linear calibration. Refers to the process of selecting one point in the
range of a data logger or chart recorder and setting it to give an identical
reading as the same point in a fully validated and verified NIST traceable calibration
standard that measures that same variable (temperature, humidity, pressure).
1-point calibrations are generally recommended for applications that require a data logger or chart recorder to operate in a very narrow range that matches the single point used in calibration, usually at ambient conditions.
1-point calibrations have the drawback of tending to pull data loggers or chart recorders out of range at points farther away from the single point calibration and therefore are not recommended for instruments that need to function over a wider range. (See 1-point, 3-point and Custom Point)
3-Point Calibration-
a.k.a. span calibration or full scale calibration. Refers to the process of
selecting three points in the range of a data logger or chart recorder at high,
medium, and low points in the instrument’s measuring range and setting
these to the same points as those found in a fully validated and verified NIST
traceable calibration standard measuring the same variable (temperature, humidity,
or pressure.)
3-point calibrations are recommended for most applications, and especially for those that are measuring conditions in a cycling environment such as refrigerators, incubators or freezers or for other applications that veer from ambient conditions.
3-point calibrations require calibration technicians to go back and forth between high-medium-and low points repeatedly to ensure that setting the data logger or chart recorder for correct readings at one extreme does not pull it out of range at the opposite point. A data logger or chart recorder’s ability to accurately measure temperature, humidity or pressure throughout its entire operating range is verified by a 3-point calibration. (See 1-point, 3-point, and Custom Point)
A2LA--
American Association for Laboratory Accreditation, a non-profit association
that provides independent verification of a calibration facility’s accuracy
(best measurement uncertainty).
A2LA accredits calibration and testing facilities like Dickson to the ISO 17025 standard. They are recognized as a third party auditor for this standard not only in the United States, but internationally as well.
A2LA was established in 1978 as a public service for all in need of standardized and reliable testing standards.
Dickson was the first manufacturer of temperature and humidity data loggers and chart recorders to become A2LA certified. (One might think that all metrology labs are A2LA-accredited, but this is not the case. Getting A2LA accreditation takes time and resources, and many metrology labs have not gone through the rigors of A2LA accreditation.)
After Calibration Data--
The readings provided by a data logger or chart recorder at any point after it has been calibrated and returned to original operating specifications.
After calibration data will not tell you if your data logger or chart recorder were operating out-of-tolerance before calibration. (See Get Before Data?)
As Received Data--
a.k.a. Before Data. Refers to the readings provided by a data logger or chart recorder before it is calibrated and returned to original operating specifications.
As received data is needed for any applications that require data on out-of-tolerance conditions.
It is impossible to retrieve as received data once a data logger or chart recorder has be re-calibrated and returned to original operating specifications. (See Get Before Data).
Before Data a.k.a. As Received Data.
Refers to the readings provided by a data logger or chart recorder before it is calibrated and returned to original operating specifications.
Before data is needed for any applications that require data on out-of-tolerance conditions.
It is impossible to retrieve before data once a data logger or chart recorder has be re-calibrated and returned to original operating specifications. (See Get Before Data?).
Best Measurement Uncertainty--
An A2LA quality rating that quantifies and defines the best a particular metrology lab can do. The ‘best measurement uncertainty’ takes into account the ENTIRE system affecting the measurements—the quality of the equipment, the quality of test chambers, personnel training, etc.
Best Measurement Uncertainty is included in all A2LA certificates in Dickson’s Compliance-Max calibrations.
The only way to compare the accuracy standards adhered to by various metrology services is to examine their published Best Measurement Uncertainty.
Calibration--
The process of re-setting a data logger or chart recorder’s readings to those of its original operating specifications. All instruments lose accuracy over time due to normal usage and the environmental conditions to which they are exposed, and calibration is the only way to ensure a data logger and chart recorder continue to operate at the accuracy level required.
(see Why Calibrate?)
Calibration Club--
Dickson’s automatic reminder service of needed calibration schedules that
Be used for data loggers, chart recorders, and all other instruments requiring periodic calibrations to ensure instrument tolerances remain within range. (See Calibration Club)
Full Scale Calibration--
a.k.a. 3-point calibration or span calibration. Refers to the process of selecting three points in the range of a data logger or chart recorder at high, medium, and low points in the instrument’s measuring range and setting these to the same points as those found in a fully validated and verified NIST traceable instrument measuring the same variable (temperature, humidity, or pressure.)
Full scale calibrations are recommended for most applications, and especially for those that are measuring conditions in a cycling environment such as refrigerators, incubators or freezers or for other applications that veer from ambient conditions.
Full scale calibrations require calibration technicians to go back and forth between high-medium-and low points repeatedly to ensure that setting the data logger or chart recorder for correct readings at one extreme does not pull it out of range at the opposite point. A data logger or chart recorder’s ability to accurately measure temperature, humidity or pressure throughout its entire operating range is verified by a full scale calibration. (See 1-point, 3-point, and Custom Point)
ISO 17025--
The most rigorous quality standard in the measurement industry.
Beyond the ISO 9000 standards, ISO 17025 include requirements specifically mandated for calibration and testing laboratories.
Note: a majority of calibration providers operating today have not achieved this more demanding ISO 17025 certification.
Dickson’s Compliance-Max calibration certificates include ISO 17025 certification.
Linear Calibration--
a.k.a. single point or 1-point calibrations.
Refers to the process of selecting one point in the range of a data logger or chart recorder and setting it to give an identical reading as the same point in a fully validated and verified NIST traceable calibration standard that measures that same variable (temperature, humidity, pressure).
Linear calibrations are generally recommended for applications that require a data logger or chart recorder to operate in a very narrow range that matches the single point used in calibration, usually at ambient conditions.
Linear calibrations have the drawback of tending to pull data loggers or chart recorders out of range at points farther away from the single point being calibrated and therefore are not recommended for instruments that need to function over a wider range. (See 1-point, 3-point and Custom Point)
NIST Traceable--
NIST stands for the National Institute for Standards and Technology. This organization is responsible for maintaining the master for different measurements, such as the standard “foot”, standard, “second”, or standard “pound”. NIST also maintains the standard for temperature, humidity and pressure. NIST Traceable means that the measuring standard can be traced directly back to the master standard maintained by the NIST organization.
NIST-Traceable does not tell you the measurement accuracy of a metrology service in any detail. Only metrology services that can document their ISO 17025 standard provided data on their best measurement uncertainty.
Out-of-Tolerance –
Refers to an instrument that is no longer operating within the measurement accuracy originally specified.
Before calibration data is always required if one needs to know if a data logger or chart recorder were ever operating in out-of-tolerance condition. (see Need Before Data).
Span Calibration--
a.k.a. 3-point calibration or full scale calibration. Refers to the process of selecting three points in the range of a data logger or chart recorder at high, medium, and low points in the instrument’s measuring range and setting these to the same points as those found in a fully validated and verified NIST traceable calibration standard measuring the same variable (temperature, humidity, or pressure.)
Span calibrations are recommended for most applications, and especially for those that are measuring conditions in a cycling environment such as refrigerators, incubators or freezers or for other applications that veer from ambient conditions.
Span calibrations require calibration technicians to go back and forth between high-medium-and low points repeatedly to ensure that setting the data logger or chart recorder for correct readings at one extreme does not pull it out of range at the opposite point. A data logger or chart recorder’s ability to accurately measure temperature, humidity or pressure throughout its entire operating range is verified by a span calibration. (See 1-point, 3-point, and Custom Point)
User Specified Temperature Point--
a.k.a Custom Point. A specific point selected for calibration either for single point calibrations or as one point in a 3-point calibration. This correlates with the usual operating range of the data logger or chart recorder in a given application. (See 1-point, 3-point, and Custom Point)