The Dead weight force machine in the range 5-50 N developed earlier was extended to a lower range of 1 N using a specially designed hanger made from aluminium alloy. This fully automated machine has been characterised in the range 1 to 20N using 2N, 3N, 5N, 10N and 20N force transducers and typical calibration results are shown in Fig.

1.4 (a) & 1.4 (b). The observed repeatability and reproducibility deviations are below 50 ppm for all the transducers in the range 50% to full scale, thus establishing the suitability of the dead weight force machine as reference force calibration machine in the range 1N to 20 N.

A very low force measuring system based on the principle of electromagnetic force compensating balance has been designed and fabricated for calibration of milli-Newton up to few Newton forces (Fig.1.5). The system is a sophisticated mechanical set up comprising of a vibration isolation table, optically flat marble table-top to ensure precision levelling and vertical alignment of the system, double walled temperature stabilized transparent enclosure, sub-micron precision translation stage, etc. The evaluation of the system with low force transducers is in progress including the traceability from the dead weight force machine, mentioned as above in the region 1-20N, by using the results in the overlapping region.

The 2.1 MN build-up system calibrated directly against NPL 1 MN reference standard machine was used to evaluate the metrological performance of the 2 MN hydraulic force calibrating machine. This work has enabled to have the traceability of the high capacity force hydraulic calibrating machine in-house up to 1 MN, which was so far based on transfer standard calibrated by PTB.

Calibration of non-conventional flange type torque transducers from industry, belonging to class below 0.5, as per DIN standard No. 51309, was carried out on torque primary standard machine using a newly designed and developed adaptor. Such transducers were so far being calibrated on reference torque standard machine, which is suitable only for class 0.5 and above. Calibration results of a typical commercial transducer showing class 0.1 for all torque values up to full range of 2000 Nm are depicted in Fig. 1.6.

The proficiency-testing program in torque measurement was initiated. Survey of the interested /participating NABL accredited laboratories was completed and the technical protocol for proficiency testing was finalised. A training program of the participating laboratories in torque wrench calibration is being planned before start of the circulation of the artefacts.

Consultancy projects funded from the Department of Weights and Measures, Ministry of Consumer Affairs, have been undertaken costing approx. more than 3 crores to design, develop and fabricate primary and secondary standard machines, for force as well as torque parameters, to upgrade the calibration capability of Regional Reference Standard Laboratories. It is emphasized here that for verification of UTMs of class I, it is required to use force proving instruments of at least class I. There are no NABL accredited calibration laboratories, except one, in the country, which can undertake calibration of force instruments of class I. NPL is therefore under a lot of pressure to carry out lower level calibration work for such instruments. In order to mitigate this pressure, NPL decided to undertake this project to design, develop and fabricate a simple, portable and user friendly force calibrating machine up to 50 kN, which can be used for calibration of such class I force proving instruments. A prototype of the designed and developed machine is shown in Fig.1.7. This machine works on the principle of force comparison using a double acting hydraulic-piston cylinder applying simultaneously the force on the DUC and the reference force transducer in series.

This work done will expedite calibration of force proving devices of class I by the force calibrating laboratories and at the same time reduce the calibration work burden of NPL.

The Vickers hardness primary standard, established last year, was evaluated for its calibration and measurement capability to be better than 0.5% for all scales HV1 to HV100 over most of the measurement range. The calibration procedure of Vickers hardness was finalised and calibration of Vickers hardness standard blocks was commenced for jobs from industry to provide traceability in Vickers hardness, which was so far not available to Indian industry.

The force and hardness standards facility is providing national traceability in force, torque and Rockwell hardness through the calibration of force and torque measuring devices and hardness blocks to various users from industries, defence and other government organisations and also from foreign countries including Kuwait, Oman and Nepal. The facilities are being used extensively, which is well reflected in the ECF of Rs 53 lakhs (approx.) and the number of calibration reports issued as 513.

Two technical personnel from Afghanistan Standardization Authority were trained in Force, Torque and Hardness measurement. A Training program was also conducted for the staff from KIMLIPI, Indonesia, the NMI of Indonesia, in Force and Torque metrology. The 2nd Indo-Italian Training program in Force, Mass, Pressure, Vacuum and Torque Metrology was conducted during 18-22 Feb. 2008 at NPL, wherein 59 participants, including 15 from ten developing countries and 44 from India attended.