Calibration standards: Introduction
4. July 2010
If you are into amateur electronics, you will have experienced a requirement for reliable calibration sources to calibrate your instruments against.
In a professional lab environment, instruments are being shipped to a calibration laboratory in defined intervals where their accuracy is validated to be within planned limits and deviations are documented. The reference source for such a calibration is in turn compared against a central standards institutions source so that any calibration can be traced back to this central source.
Unfortunately, conducting such a calibration is often far beyond the reach of amateur means and often exceeds the instrument value (which is probably why the same is then written off).
In the past I was fairly surprised to find out that my (simple) instruments are deviating significantly from each other and I had no reliable calibration sources to validate them against so I just arbitrarily defined one of my meters as the "master" against which all other instruments are being calibrated.
Over time I had the desire to achieve a better understanding and quantification of accuracy and precision of my instruments so I took the time to build some hardware to help me with that task.
The intention of this small series of articles is to present simple means for calibration and help with judging whether or not an instrument needs to be adjusted. If you, like me, own mostly old instruments pulled from work environments, you will be surprised about your findings during the calibration process.
Calibration standards: DC voltage
30. June 2010
One of the cheapest and most effective calibration standards that can be easily homebuilt it the DC reference voltage standard. It can be used to calibrate DC ranges of volt meters and multimeters and can serve as the basis for AC calibration and DC current calibration too. Best of all, it is fairly affordable thanks to the availability of modern semiconductor chips.
Calibration standards: Resistance
30. June 2010 Yet another one of the dirt cheap calibration standards that should be available in any hobby electronics workshop.
Calibration standards: AC voltage
11. July 2010 Calibrating an instrument that indicates AC voltage is a surprisingly big challenge for various reasons. If the instruments is geared towards RF frequencies (such as an RF Milliwatt meter), the standard of choice should be the RF level generator presented elsewhere on this website.
Should the instrument however be a regular AC voltmeter as it comes as part of every multimeter, it is necessary to first clearly understand the parameters involved in the measurement.
Calibration standards: Frequency
4. July 2010
Frequency calibration is a wide field. It can range from a simple verification of a radio frequency to the creation of an independent frequency standard to supply to various devices in the lab that allow for external time bases (counters, generators, oscilloscopes).
Generally, small errors can be tolerated but certain appications exist that require a time base accuracy of 0.1ppm or better, such as WSPR (radio communication with extremely weak signals).
Such an accuracy can be achieved if the influencing parameters are understood, procedures are being followed and/or some additional equipment is being built.
Calibration standards: RF level generator