Calibration Made Simple
As a manufacturer of high-accuracy measurement products, National Instruments
understands the need to maintain properly calibrated equipment. Calibration is the
comparison of an instrument’s actual measurement performance to a standard of known
accuracy. With calibration, you can achieve the following:
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Ensure accurate measurements
Trace measurements back to known and accepted standards
Increase production yields
Meet quality program requirements such as ISO 9001
Provide a basis for comparing measurements between different users
Critical for maintaining performance and accuracy, calibration can be performed on a wide range of instruments.
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Calibration Intervals
The accuracy of the electronic components of all instruments drifts over time, with factors such as time in service
and environmental conditions contributing. Devices are designed and tested so this error is noted in accuracy
specifications, but after a defined length of time called the calibration interval, most manufacturers no longer specify
the measurement accuracy. To maintain specified measurement performance, instruments must be calibrated at regular
intervals as defined by the manufacturer.
Self-Calibration
Self-calibration, or internal calibration, uses onboard signal references to adjust measurement accuracy. During
self-calibration, the instrument measures the onboard references and adjusts its measured performance to account
for changes due to environmental effects such as temperature.
The adjustment of measured values during self-calibration does not account for the drift of the onboard signal reference
and does not replace the need for external calibration. Performing regular external calibration helps ensure the onboard
reference signals are accurate and maximizes overall measurement performance.
External Calibration
0.01%
24 Hours
90 Days
1 Year
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Error
Time
There are a number of reasons to send an instrument to the manufacturer or a suitable metrology laboratory for external
calibration, including when you need to verify performance, when the calibration interval has expired or your predefined
service time has elapsed, when the instrument has been operated in an extreme environment, or when measurements
appear questionable. External calibration includes verification of the instrument’s capabilities and provides for adjustments
to measurement circuitry and onboard signal references if needed. Typically, a calibration certificate is issued verifying the
instrument’s measurement performance at the time of calibration.
System Calibration
System calibration, the most comprehensive method of calibration, quantifies and compensates for the total
measurement error in a system. By applying known inputs and reviewing the resulting measurement, you can develop a
model that represents the error of the system and compensate for this error by applying correction coefficients to your
measured data.
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Accuracy Specifications
For most computer-based data acquisition and instrumentation hardware, NI supplies graduated accuracy tables.
ni.com/calibration
Computer-based data acquisition and instrumentation hardware is ideal for this type of compensation because you can
quickly and easily apply your correction in software. System calibration does not completely replace the need to perform
external calibration on individual system components in order to meet the requirements of quality programs.
ni.com/calibration
NI [ NATIONAL INSTRUMENTS CORPORATION ]
