Foil strain gauges
At foil strain gauges a pickoff is executed from foil in thick 3..6 мкм.
Thickness of foil strain gauges less than wire and 30..50 mkm makes. Basic advantages of foil strain gauges it is been possibility of formation of tenzo grates of any form and effective taking of heat in the process of measuring, that allows to get a greater output signal at identical deformations. Foil strain gauges are not sensitive to transversal deformations and assume малобазное execution beginning from a 0,3 mm and higher.
Tenzo grates of domestic foil strain gauges, as a rule, make from constantan foil (ТУ-ЦМО- 03 № 96-67). Electromechanics properties of foil within the limits of one party as compared to constantan тензопроволокой differ in less constancy, and her heat treatment is less effective, therefore the working range of foil strain gauges does not exceed ±3000..5000 mln^ -1, and temperature - 75..575 К. Technology of making of foil tenzo grates is usually based on the use of actinic processes and in a most degree adjusted for a mass production. Foil strain gauges divide into next model modifications depending on the form of tenzo grates (fig. 1) : single-element rectangular for the linear measuring; two - or three element rectangular or rosette-like for measuring on areas with the flat tense state; special, used as tenzo transducers in membrane pickoffs; as chainlets of with a small base one - or two - element tenzo grates on general basis for measuring of deformations in the areas of concentration of tensions.
Domestic industry mass-produces the foil strain gauges of next tipo sizes : single-element strain gauges of types of 2ФКПА, 2ФКПД, 1ФКТК, ФК-ПА, ФК-ПБ and ФК-ПВ on pellicle basis with bases a 0,8..20 mm and by resistance 50.. ..400 Ohm; two - and three element strain gauges of types of 2ФКТК and ЗФКТК on pellicle and paper basis with bases a from 5 to 15 mm and by resistance from 100 to 400 Ohm; rosette-like strain gauges of types of 2ФКРВ, 2ФКРГ, ФК-РА and ФК-РБ on pellicle basis with bases a 0,8.. 10 mm and by resistance 50.. 140 Ohm; special for the membrane resilient elements of electromechanics transducers of types of 2ФКМВ and 2ФКМГ on pellicle basis by a diameter a 10..30 mm and by resistance 50..200 Ohm.
The strain gauges of the transferred types are intended for measuring in the climatic range of temperatures (225..325 К), and also at enhanceable temperatures - ЗФКТК (265..475 К). Recommended assembling glues: cyacrin ЭО for the strain gauges of 2ФКПА, 2ФКПД, ФК-ПА, ФК-ПБ, ФК-ПВ; glues of БФ- 2 and ВЛ- 9 for the strain gauges of 1ФКТК and 2ФКТК; glue of ВЛ- 4 for the strain gauges of ФК-ПА, ФК-ПБ, ФК-ПВ, ФК-РА and ФК-РБ; varnish of ВЛ- 931 for the strain gauges of 2ФКНА, 2ФКПД, 2ФКРБ, 2ФКРГ, 2ФКМВ and 2ФКМГ.
Maximum measureable deformation ± of 0,3%, creep at T= 295 To not over 0,5%.