Re: Frequency Standards
And that I think is the point.
If you have a primary standard, which something like a cesium standard is (I think) then you don't need a calibration ticket. Secondary standards which are derived need calibration tickets.
I think that if I can show that I am deriving my reference from a maintained standard (Droitwich in this case) and document that fact as a "before using the test gear it is checked against......." then I am ok.
An example is the manometer that we use to check airspeed indicators. This is a water column, mercury for high speed ASIs, and the effective speed is given by the air pressure that supports the water to a given height. Gravity is always switched on and to all intents and purposes doesn't change. The scale marking distances don't change. It has water in it and water is water for the purposes of the test. This is a primary standard as it is a direct representation of the physical quantity that you are measuring.
An example of the sort that requires a ticket is the altimeter that is used to check other altimeters. This will require regular recalibrating as the mechanism can wear or start building up a bit of friction. This is a secondary standard and requires a regular ticket. Fortunately it is one that is fairly simple to do.
Robin
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