GB649490A - Plating thickness meter - Google Patents

Abstract

649,490. Electric tests &c. current measuring. CARNEGIE-ILLINOIS STEEL CORPORATION. Sept. 29, 1948, No. 25407. Convention date, June 8. [Class 37] [Also in Group XXXVIII] The amount of thickness of metal electrolytically deposited on a moving strip S in a bath 2 is measured by deriving and comparing potentials proportional to plating current and strip speed. Separate anodes 8, 10 on opposite sides of the strip S are fed from separate generators 14, 16 the two generator currents and hence the thicknesses deposited on the opposite sides of the strip being compared in a ratio meter 30 which may be provided with auxiliary contacts 37 to actuate signals or control the ratio. The total plating current passes through a shunt 38 to produce a proportional potential drop across series connected resistors 46, 48. A tachometer generator 54 driven by the strip feed rollers 12 produces a potential proportional to the strip speed across a potentiometer 60 the moving arm 68 of which taps off a fraction of this voltage which is normally balanced against the potential drop across the resistor 46 in a contact making galvanometer 44. If the balance is upset the galvanometer at its contact 76 energizes the appropriate field 81 of the series motor 70 whereby the motor rotates in the corrective sense to restore the potential balance by adjusting the poteniometer arm 68 and at the same time actuating a pointer 82 to indicate the deposit thickness or amount in lbs. per base box. Variations in width of the strip are catered for by a potentiometer 58 manually set in accordance with the width to vary the proportion of the tachometer voltage applied to potentiometer 60. A similar potentiometer 50 set in accordance with the plating efficiency adjusts the potential across resistor 46. To return the indicator 82 to zero when the bath 2 is not functioning a voltage derived from an A.C. source 100 and rectifier 86 is fed to the potentiometer 60 to cause the motor 70 to zeroize the pointer. This voltage is disconnected during normal working by a relay 92. The potentiometer 60 may also be provided with contact making mechanism to operate an alarm should the coating thickness deviate beyond allowable limits.