An article from the early 80s

Sent in by Neil Caldecourt

Telecom's calibration service

The work of BT's 16 laboratories

A CALIBRATION service is provided by the Quality Assurance Division, which is currently responsible for calibrating over 40,000 instruments comprising some 500 different types. The division's 16 calibration laboratories provide a uniform standard ofmeasurement, with traceability to national standards.

The regular calibration of instruments is necessary to ensure that they are operating within their specification limits and to their full capabilities.

The laboratories calibrate and repairequipment used in the frequency range from DC to microwave. This includes audio,carrier and coaxial test items, cable and line test equipment, radio test equipment, microwave, PCM and Datel test equipment, analogue and digital meters, oscilloscopes, spectrum analysers, video equipment and many other measuring instruments. Some of the calibration equipment used in the division is unavailable elsewhere in BT - if at all. One example is a programmable automatic test rack used for FDM, microwave and radio station equipment. Developed inhouse, it has reduced sevenfold the time taken to calibrate a Selective Level Measuring Set No 244A, which previously was calibrated manually. Facilities are also available to repair faulty equipment before itis calibrated.

Data obtained from calibration and repair work provides valuable information on design and component reliability, which means that QA division can offer useful advice on the suitability of new purchases.

The regularity with which an instrument should be returned for calibration is dependent upon the instrument type and not upon the degree of usage it receives. Components themselves have deterioration characteristics which will cause problems even if the item is seldom used. Every week, as part of the service offered, 19 vans leave the division's London and Birmingham premises to collect test equipment from all over the UK mainland for calibration and repair. (Items are flown in from Northern Ireland.) A loan of equipment is often provided and the calibrated or repaired items are returned, usually within two weeks of collection. The speedy turnaround of the loan/transport service ensures minimum inconvenience and disruption to users of the calibration service.

Once an instrument is registered for calibration, the responsibility for maintaining its measurement accuracy throughout its working life is accepted by QA Division. To facilitate the smooth running of this commitment a computerised schedule is produced, whereby items are automatically 'called in' for calibration at regular intervals. It also ensures that the demands for equipment loans and transportation can be met.

Independent organisations have shown considerable interest in the calibration facilities available and requests for BT to provide a consultancy/calibration service are not infrequent.

A list of items currently calibrated is published and is continually revised to take account of changes in BT measuring equipment.

Enquiries to: MSP5/QA2.3.1.1 (01-226 1262 x390).

PR3.1.5.2 (01-357 3735)

Picture:-Automated supply and measuring system an in-house development by the calibration team - Dave McNeil?

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