- To avoid ambiguity, when referring to a pressure value it is important to specify its mode.
- The solid-state 60 kHz transmitter at Anthorn typically operates at around 27 kW of radio-frequency signal which gives an equivalent monopole radiated power of approximately 17 kW.
- See our Good Practice Guidance Note.
- In scientific circles the word balance has many meanings but in the context of weighing it originates from the abbreviation of beam-balance - where the weight of a sample or artefact contributes to the balance of moments of a beam about a central fulcrum.
- There is no fixed period for the validity of a calibration certificate - it is not like your cars MOT certificate. However, measurement results stated on certificates are usually 'on the day' values and no allowance is made for subsequent drift.
- Many members of Pressmet (EMAN's Pressure Measurement Special Interest Group) can supply, calibrate or repair such apparatus.
- When requesting a calibration it is reasonable to try and establish beforehand something about the measurement uncertainties that are likely to be provided on the ensuing certificate; unless they are going to be adequate there is not much point in asking for the calibration.
- The words accuracy and uncertainty are sometimes interchanged but the difference between them is significant and, in many applications it is vital.
- Values of atmospheric pressure in Teddington, measured at about 10 metres above sea level, going back to 1 January 1998 and shown both graphically and digitally, can be found on the historical pressure page of the NPL on-line barograph.
- No, they are not. The internationally recognised SI unit for pressure is the pascal, abbreviated to Pa, and this is the unit realised by the primary measurement standards in the world's national metrology institutes to provide traceability for pressure measurements.
- The International Prototype Kilogram is not perfectly stable (its mass changes with time), the amount it changes cannot be known perfectly (there is no 'perfect' reference against which to judge it) and the values of the national copies cannot be monitored at the highest level of accuracy without being compared directly with it.
- The most accurate barometers are indeed the mercury primary barometers used at national measurement institutes. Most barometers, though, are secondary instruments rather than primary ones and when considering these it is not correct to say that those based on a mercury column are invariably more accurate than those that are based on an alternative principle.
- Yes there are - some are listed here.
- The time at which summer time begins and ends is given in the relevant EU Directive and UK Statutory Instrument as 1 a.m. Greenwich Mean Time (GMT).
- Up to a point yes, but unless a weight is of suitable design and material and in appropriate condition it will not be possible to give it a meaningful calibration and it would certainly be a waste of money.
- Give the weight a general inspection to check its construction, surface finish and the suitability of its magnetic properties.
- A number of factors need to be taken into account when considering sources for calibrating radiation thermometers.
- Yes - Saturated (or unsaturated) salt solutions, and certain other chemicals, can be used to generate an environment of a particular relative humidity in an enclosed space.
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