Terminology

Butterfly

Calibration Table

Also known as a “step-table”. In seismology we commonly refer to step tables as “calibration tables” which can be confusing. A more accurate term would be “verification table” as a calibration table cannot actually be used for “calibration”, only verification of the vertical/ horizontal gains.

Precision and accuracy

Calibration should be as precise and accurate as possible.  Many times those terms are used interchangeably even though they are different.  There are many influences that can affect the quality of your calibrations.  Temperature, vibration, weight of the sensor, touch of the operator, limits of the dial indicator, leveling of the equipment, wear in the bearings and maybe even how much coffee you had that morning.

We think of precision in this way: If we ask you to weigh an object ten times and you put it on your scale ten times and it weighs exactly 3.95 kilos every time, then your scale is very precise.  Since we know that the object weighs 4.00 kilos then we know that your scale is not very accurate.

The very best dial indicators like the one used in the OSOP Calibration Table have a precision of 1 micrometer and an accuracy of +/- 0.8 micrometers (see Specifications). The price and trouble to get even a little more accuracy are probably not worth it.

At OSOP we build our calibration tables one at a time so your observations and suggestions are always timely and welcome.

Step Table

See above: “Calibration Table”.