Patent GB-1009712-A (GB)
Title: Electrochemical apparatus such as coulometers
IPC: G07C3/02
Filed: 1961-12-28
Abstract: 1,009,712. Smoothing D.C. AMERICAN MACHINE & FOUNDRY CO. Dec. 28, 1961 [Jan. 3, 1961 (4)], No. 46463/61. Heading H2F. [Also in Division G1] An electrochemical coulometer cell wherein the transfer of an ionic species within . an electrolytic solution is a function of the magnitude of, or time during which, an electric current is applied thereto, comprises an integrally constructed hermetically sealed housing having an internal chamber, with a filter impermeable to the ionic species except electrolytically arranged to divide the chamber into two sections by rigid and fluidtight fixture within the housing; the sections communicating with each other only through the filter and one of the sections containing a quantity of the ionic species while the other is adapted to receive and concentrate such ionic species during operation of the apparatus; with contacts extending into each section for connection to a current source. For electrolytically measuring the time of position of a mechanism, e.g. an aircraft, such operation switches a stabilized voltage source to energize an electrolytic cell (Figs. 1, 2, 3) having a glass or transparent plastic housing 22 with a graduated front panel in which are formed chambers 24, 26. A microporous separator 32 held between a shoulder 34, seal rings 36, 38 and a diaphragm 40 divides chamber 24 into sections 10, 14; the latter having an elongated dependent bore 28 formed with a radial groove 30. Cathode 20 upstands through cemented plug 48 into bore 28 of section 14, while anode loop 18 upstands between rings 36, 38 into section 10 and is cemented to body 22. Cap 52 with annular groove 54 receiving diaphragm 40 fits into opening 44 of the housing, and is sealed into position with e.g. epoxy resin to leave an evacuated chamber between its inner face and the diaphragm to compensate for unequal expansion within the sections 10, 14 of chamber 26. The diaphragm may be of plastic coated glass fibre or microporous P.V.C. while the seals and diaphragms may be of silicone rubber and the anodes and cathodes of platinum or molybdenum wire or platinum coated nickel/iron wire. Sections 10, 14 are filled with an aqueous solution of lithium and mercuric iodides, and section 10 contains a quantity of mercury 12. A rectifying or smoothing circuit for supplying a stabilized current to the cell in series with connection terminals 64, 66 is enclosed in chamber 26 with phenolic or epoxy potting resins, and interconnection of the terminals during operation of  the mechanism deposits mercury by electrolysis on cathode 20, which collects in bore 28 as a column which may be read in slot 78 of panel 72 against indicia 74 of the elapsed operating time. The stabilized current supply circuits may comprise (Fig. 6) a silicon diode rectifier 122 fed from A.C. supply over series resistor 120 and optional R.C. smoothing circuit 140, 142. To engage neon stabilizer 124 across the supply to the cell in series with resistor 126 (Fig. 7, not shown); a single anode regulating Zener diode fed in shunt from A.C. supply through a series resistance to energize the cell over a series positive temperature coefficient compensating resistor; the circuit of Fig. 6 with the rectifier placed after the neon stabilizer (Fig. 8, not shown); a double anode Zener diode corrected in shunt across a D.C. supply through a series resistor 100 to supply stabilized current through a positive temperature coefficient resistor 104 (Fig. 9) or a circuit in which the resistor 100 is replaced by tungsten lamp (Fig. 10, not shown). The neon or tungsten lamps may illuminate the indicating mercury column and/or the indicia.