Calibration is employed into digital multimeters and other instrumentation to ensure accuracy and consistency. Instruments are configured to an acceptable range using measurements from a known source. In short, where accuracy and reliability are paramount, Fluke calibration should be factored in when buying a multimeter.
Definition: A trustworthy signal that a multimeter can garner correct readings from a given circuit to be relied upon – results are compared with a reference device that has ‘known’ accuracy.
In certain incidences, especially those of an electronic nature, you will need to rely on your meter to give you the exact (or as close as possible) reading, whether resistance, voltage, current, capacitance, and so on.
The caveat when you calibrate Fluke multimeters is that the reliability of the results is also attributed to environment – ambient temperature, humidity, pressure (altitude) and so on. These criteria will all weigh on noted specifications, as will line voltage and low battery level.
An electrical calibrator is used to perform the task of multimeter calibration, which they also sell, or you can send your meter off to be professionally calibrated.
All multimeters tend to lose accuracy (‘drift’) as they age, though it is less of an issue today compared with older technologies. They will thus need to be periodically re-calibrated. This period is written into the specification of the DMM. If you don’t adhere to it, the table of accuracies may no longer apply.
The typical period of calibration is one year, although more exacting devices’ specifications may have a 90-day period. This might apply to a high-digit bench device used to troubleshoot lab equipment, for example, while an average 3 3/4-digit general purpose handheld meter will likely be good for a number of years.
It ultimately depends on how important the task at hand is and the intended accuracy. But a Fluke multimeter that is rarely calibrated will likely be more accurate than a non-Fluke meter that is less frequently calibrated. They tend to hold their specs well. Reports of 15-20-year-old Flukes cranking out the same tight accuracy as the day they were bought are commonplace.
Tests are traceable to System International (SI) units. Devices are returned with certificate and seals and sequentially recorded by the meter.
ISO 9000: Traceable Calibration
The multimeter is calibrated using NIST (National Institute of Standards and Technology) laboratories, or another standardized laboratory, to the specifications laid out by the manufacturer before use or periodically. More on ISO 9000 standards…
ANSI/NCSL Z540: Accredited Calibration
Calibrated under a national accrediting organization to this standard and delivered with accredited documentation. Unless you specify, the certificate will not state future intervals.
Z540: Traceable Calibration
Calibrated at periodic intervals to ensure reliability and returned with ‘Report of Calibration’. As Left or As Found stickers denote test uncertainties.
Fluke calibrate/repair labs are 17025 and ISO 9001:2008-accredited.
Price: Calibration typically comes at a flat rate and covers labor and equipment costs, together with a tamper-proof sticker/seal.
Types of Equipment
Fluke can support most test requirements, including temperature. Together with all their test equipment, they can also calibrate devices from other manufactures, such as Keysight and Klein.
- Handheld multimeters and bench meters
- Current amp clamps
- Oscilloscopes (digital and analog)
- Power analyzers
- Pressure meters
- Frequency counters
- Network test tools
You can also self-calibrate Fluke multimeters with a calibration tool. Access to calibrate mode is through a series of button combinations, which will be stated in the meter’s manual. Your device will also show how many times it has been calibrated.
The calibrator should have the qualities to match the functionality of your multimeter and better the specifications by at least four times.
Note: Zeroing a multimeter through an on-board ‘calibration’ button is not calibrating it. Some of the cheaper meters tout such a mode; others simply adjust for humidity and temperature ambient. In reality, they will require an accurate on-board voltage reference. This will unlikely be the case with the cheapo meters and is generally a marketing gimmick. As noted above, true calibration requires the comparison with an instrument on orders of magnitude more accurate. Auto-calibrators are a different kettle of fish and tend to be reliable.
Fluke offers an excellent and reliable calibration service. It’s not cheap, but if you are involved with accurate systems, undergoing periodic calibration is recommended and often essential. For general DIY work, this will hardly be necessary and it may be cheaper to just buy a new meter altogether. In addition, Fluke multimeters also tend to retain their accuracy over time.