FAQs
FAQs Areas
Random FAQs
- The relationship between the kilogram and the pound is defined exactly as: 1 lb = 0.453 592 37 kg.
- Certified Reference Materials (e.g. Primary Reference Gas Mixtures) produced by NPL under ISO Guide 34 will have an expiry date stated on the certificate.
- Your barometer is undoubtedly scaled in inches of mercury - properly abbreviated to inHg (with only the 'H' a capital letter).
- The ITS-90 (International Temperature Scale of 1990) defines procedures by which certain practical thermometers of the required quality and precision can be calibrated in such a way that the values obtained from them can be precise and reproducible, while at the same time representing the corresponding thermodynamic temperatures as closely as possible.
- Probably not. The figures should be interpreted with caution, especially if an instrument has not been independently calibrated for some time.
- We would recommend that reference flats in interferometers be recalibrated every three to five years depending upon the precision of measurement required.
- A thermistor is simply an electrical resistor whose resistance changes rapidly with temperature.
- The length of time that it will take for the step gauge to reach ambient temperature in the laboratory will depend on both its mass and the temperature differential between the car boot and the laboratory.
- In 1998, the Consultative Committee on Amount of Substance (CCQM) defined that traceability to the SI could only be achieved by the use of a primary method. In the case of gas standards the most relevant method is gravimetry.
All FAQs
- No. Since 1983 the metre has been re-defined in terms of the speed of light and is realised using laser wavelengths.
- The short answer is 'both', because the use of the word midnight is heavily dependent on its context.
- There should be no interference as the Wi-Fi transmit frequencies are so different from the MSF frequency.
- Yes it can in some circumstances but, where it does, it is fairly easy to ensure that its effect on the measurement uncertainties obtained is negligible.
- Yes it does - provide that you mean the 'scientific' definition of weight where the weight of a body is the gravitational force acting on it and hence it should be measured in newtons; this force depends on the local acceleration due to gravity.
- Yes, but unless you are making weighings at the very highest level of accuracy, the consequences are probably too small to worry about.
- No, but there are at least two companies that do.
- Not for a long time, and we are unsure of any companies that do?
- It depends on the exact item. Generally we try to offer calibrations in imperial units, where we have the facilities available.
- The answers to some frequently asked questions about mass and force metrology.