22 ANALYTICAL & LABORATORY EQUIPMENT
➠
manufacturer’s application knowledge and services available. All these factors contribute to the actual user- experience and operational success.
Regular traceable calibration
One should always make sure that the data produced by the measurement equipment is reliable and accurate. Periodic calibration is absolutely essential. Typical calibration intervals can be viewed in Table 1. Table 2 presents an example of a traceability chain for
installed humidity and temperature units. From a global perspective, all measurements are based on the globally agreed International System of Units (SI). This ensures that we use the same quantities, and that measurements performed with various types of equipment in various locations are comparable. National laboratories are responsible for maintaining
and developing traceability and for providing the highest accuracy calibrations. The services of the National Measurement Standard Laboratories may be limited to calibration of the highest grade primary standards. Commercial calibration services provide calibration
services for lower level standards and measurement equipment. These may be manufacturer services providing calibration services for their own products, or laboratories providing calibration services for any measurement equipment. Non-accredited calibration services are the majority service providers, including
most of the measurement equipment manufacturers’ calibration services and a considerable amount of commercial calibration services. Without accreditation the competence of these services is not proven. The competence should be confirmed by auditing the service. Each calibration service provider must maintain an
effective traceability chain. The primary standard must be calibrated at an outside laboratory and then used for calibrations. Some commercial calibration services do not include uncertainty estimations in their calibration certificates if not ordered separately. Some calibration services are not able to calculate uncertainty at all. One should always consider the competence of these services. Laboratory calibration is preferred to field calibration.
In a laboratory, the effects caused by the environment can be minimised, and the number of factors influencing the calibration are reduced significantly. Field calibration is a quick and easy way of checking
measurement equipment without having to remove it from the process or process area. Field calibration requires a working standard as a reference. This working standard can be hand-held or some other equipment used for calibrating the instrument installed in the process. Working standards are calibrated at a higher level laboratory. u
Daisuke Fujisawa is Regional Market Manager with Vaisala, Tokyo, Japan.
www.vaisala.com
Circle 22 or ✔ at
www.scientistlive.com/elab
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44