MOP1-4.

E ~ E ~ ~ E ~ ~ E OF METAL FOIL BASED 100 Sa PRECISION STANDARD RESISTORS

P. Warnecke. H. Leontiew, E. P e d . and B. Schumacher Physikalisch-Technische Bundesanstalt

P.8. Box 33 45, D-38023 Braunschweig, Germany

Y.A. Zaslavskij YURTMOV, 350010 Krasnodar, Russia

Abstract

We report on the pressure dependent behav- iour of 100 R precision standard resistors whtch had been fabricated on the basis of metal foil resistors (type MC 3020. Krasnodarsky ZIP, Russia). The measure- ments were performed in the range 900 to 1100 Wa using a temperature regulated pressure cell.

Introductiom

The value of resistance depends on the physi- cal parameters of the surroundings, e.g. temperature. pressure. and humidity. Usually these parameters are monitored and - in the case of temperature - stabilized. Due to deviations from the nominal values of tempera- ture T and pressure p corrections for the resistance values are made using the dependences R(T,p) which have to be established experimentally for each individ- ual resistor. A prerequisite for meaningful corrections is a reversible response of the resistance on changes of temperature or pressure. It is well known that precision standard resistors can irreversibly be changed by trans- ports. these changes being of the order of several prts in 10'. It had been shown that even temporary changes in the maintenance temperature of the resistors, being ofken the case during transport, cause the above men- tioned irreversible resistance changes [ 11. The relative pressure dependence of resistance is rather small (in the order of lO-'/hPa) for Thomas-type resistors [2] but has to be considered with respect to high precision meas- urements. From high resolution measurements of the pressure dependence of 1 $2 Thomas resistors we got indications to a hysteretic and irreversible behaviour, which makes the interpretation of the results of inter- national resistance comparisons between metrological instituts being at rather Merent altitudes more Hi- cult. Precision standard resisitors which had been fabri- cated on the basis of metal foil resistors (Krasn-b ZIP. Russia) seem to have good properties as travelling standards with respect to the dissemination of the unit of resistance and international comparisons [3].

Here we report on the influence of controlled changes in the air pressure on the long term behaviour of 100 Q precision standard resistors which are im-

proved versions of the type MC3020 ZIP. Experimental results will be presented at the conference.

References

[ 11 H. Leontiew, and P. Wamecke, "Non- reversible behaviour of precision standard re- sistors due to changes in the maintenance tem- perature", PTB-Mitteilungen. vol. 102, pp. 289-290, 1992.

[2] R.F. Dziuba, "Pressure Dependencies of Stan- dard Resistors", Conf. Proc. NCSL Workshop & Symposium, pp. 363-369, 1993.

[3] Yu.V. Tarbew, AV. Ploshinsky, I.V. Khak- hamov. P. Warnecke, and E. Pesel, "Comparison of Quantized Hall Resistance Measurements between IMM and PTB", Di- gest Cod. Prec. Electrom. Meas. CPEM '92, Paris, pp. 290-291, 1992.

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