38 schlink: hysteresis of indicating instruments 



Distribution: Trinidad to eastern Brazil. 

 Specimens Examined. 

 Trinidad: Broadway 2504, 2564, 2627; Bot. Card. Herb. 2303; 



Hitchcock loooi, 10063, 10117, 10136. 

 Venezuela: Santa, CataMna, Rusby <Sf Squires ;i 58; Island of Mar- 

 garita, Miller & Johnston 184. 

 Brazil: Rio Branco, Kuhlmann 3358; Ceara, Gardner, 1889, 1894. 



TECHNOLOGY. — -The determinateness of the hysteresis of indi- 

 cating instruments . F. J. Schlink, Bureau of Standards. 



STATEMENT OF THE PROBLEM 



The purpose of the present paper is to set down briefly the 

 results of one of several concordant preliminary experiments 

 carried out to determine to what extent hysteresis or variance 

 determinations with respect to nonintegrating mechanical mea- 

 suring instruments are themselves sufficiently definite and re- 

 producible to warrant wide application in instrument testing, 

 calibration, and utilization. The conclusion is reached that 

 no extraordinary experimental care is required to arrive at 

 hysteresis determinations of very definite utility, and that, 

 under stated conditions, such determinations are of a highly 

 reproducible character. These results are forecast in a paper 

 just completed by the author, to which the reader may refer 

 for a general discussion of hysteretic cycles in the operation of 

 measuring instruments and of the fundamental relation which 

 such cycles bear to testing and calibration.^ 



apparatus and method 



In order to minimize the experimental difficulties and to per- 

 mit of useful generalization of the results of the investigation, 

 the instrument chosen as the basis for this work was a spring- 

 controlled self-indicating weighing scale of the stabilized-plat- 

 form pointer-and-dial type, a sort commonly used for the weigh- 

 ing of postal and express parcels, and to a very limited extent 

 of vegetables and other low-priced commodities of trade. 

 The choice of this particular type of instrument, shown dia- 



1 The concept of resilience with respect to indicating instruments. To be published 

 in the Journ. Franklin Inst., February, 1919. 



