GB258568A - - Google Patents

Abstract

258,568. Atlantic Precision Co., (Assignees of Allen, A.). Sept. 17, 1925, [Convention date]. Capacities, measuring. - In a method of measuring the amount of material taken up by a web in coating &c. operations, the weight of the web is measured by the capacity of a condenser consisting of two spaced plates between which the web is passed. To indicate the capacity changes, the condensers are included in two oscillatory circuits which are tuned to resonance. The web w is passed between two plates 1, 2, through the treating apparatus, for example, a bath 5, and then between two plates 15, 16. The oscillatory circuit A comprises a thermionic valve 20 the plate circuit of which is tuned by an inductance 23 and a variable condenser 24. A coil 25 is inductively coupled to the coil 23 and connected through a grid leak 26 to the grid 27 of the valve. The plates 1, 2 are shunted across the .condenser 24 and constitute a capacity which varies with the weight of the treated web. The whole circuit may be enclosed in an earthed shield 30. Extending from the shield is a loop 31 with which the receiving circuit B is loosely coupled. The circuit B comprises a coil 32 in circuit with which are two variable condensers 33, 34 in parallel with each other and with the plates 15, 16. Coupled to the circuit by a transformer is a thermo-galvanometer 40 or other current indicating instrument. The circuit A is tuned to a suitable frequency, and the circuit B is tuned to resonance as indicated by the maximum current flow in the instrument 40. Any change in the capacity of the condenser 15, 16 owing to variation of the weight of the treated web will throw the circuit B out of resonance with the circuit A, but resonance may be restorer! by adjustment of the condensers 33, 34. The amount of adjustment measures the change of capacity of the plates 15, 16 due to change of mass of the treated web. Possible variation of capacity due to change of weight of the web itself is eliminated by the passing of the web between the plates 1, 2, so that the adjustments of the condensers 33, 34 measure only the variation of the weight of the treating material taken up. Instead of adjusting the condensers 33, 34 to bring the circuits into resonance, the circuit B may be maintained slightly out of resonance, and the changes of current value become a direct indication of the changes in capacity due to the treating material taken up. The instrument 40 may be calibrated to show directly the running weight of material taken up. Measurements may be taken with the web stationary between the plates. Specification 276,469 is referred to.