Dec. 24, 1946. _ w. FSWOLFNER, 2D 2,413,020 ELECTRONIC RELAY Filed May 19, 1945 I?” — ‘lamina-AB ‘ 1/9” %_ //7.>\ 4. 51322327 [/5 M9105 p}, \ j - 621050;” \ Vb 14/ _ > ‘ / ~ Z5 . fwaivivlr éyW Patented Dec. 24,1946 » 2,413,020 UNITED STATES PATENT OFFICE 2,413,020 ELECTRONIC RELAY William F. Wolfner, II, Asbury Park, N. J ., assign or to Photoswitch Incorporated, Cambridge, Mass., a corporation of Massachusetts Application May 19, 1943, Serial No. 487,671 5Claims. .(Cl. 250-27) ~ 1 2 The present invention relates to electronic de ad ‘form a conventional diode. It will be under vices and especially to relays which respond to stood that two separate tubes, a controlled elec changes of the value of a detecting impedance. tron discharge means and an uncontrolled elec Some of the principal objects of the invention tron discharge means each in its individual Vessel, are to provide a relay of the above-mentioned may be used and that the tube or tubes may general type which is very sensitive and detects include conventional supplementary electrodes comparatively slight changes, such as of the order such as suppressors and screens. of less than 5% of the value of the detecting im A bridge net-work Nl comprises a probe con pedance in the input circuit, but which is suffi denser Cl, a bridge condenser C2 and two re ciently rugged to permit use in industrial in 10 sistors RI and R2, one of which may be con stallations as for example as level detector, to tinuously adjustable and the other of the ex provide an electronic device containing a detect changeable plug-in type. The probe condenser ing bridge circuit coupled to an ampli?er through Cl may consist of two plates l and 2 forming a a separate sensitive unbalance detector, to pro gap 3. If the device according to the invention vide a voltage detecting circuit which reacts only is used as a level detector, plates I and 2 will be to change of a controlling voltage in one direc vertically arranged so that gap 3 will contain tion, and to provide an electronic detecting cir liquid or another agent 4 con?ned in tank 5, when cuit which can be regulated to react to an event the level of that agent reaches the probes. to be detected with an appreciable time delay so Cathode kl of tube Tl is connected to a point 0 that premature or accidental operation is fore 20 between condenser C2 and resistor El, and grid stalled. gl is through a limiting resistor connected to a One important feature of the invention, the point 112 between condenser Cl and resistor R2. above-mentioned unidirectional unbalance de The outer terminals of condensers Cl and C2 are tector, includes potential apportioning triode and connected to line B, and the outer terminals of diode circuits on either side of a condenser whose 25 resistors El and R2 are connected to adjustable charge changes with the changing controlled con tap S of potentiometer R6. Plate at is connected ductivity of the triode and affects a control poten to line termbinal A in series with a load re tial derived'from the rectifying diode. In an sistor R3. other aspect, the invention involves conversion The anode ad of the diode portion of tube Tl of a controlling alternating voltage, derived from 30 is connected to a voltage combining and rectify and in phase with the voltage of a conventional ing load network N2 comprising a capacitance supply line, into an alternating voltage of a phase means such as condenser C3 which is connected in opposition to the supply phase and hence at x, y respectively, between the two anodes at adapted to provide a blocking potential to a tube and ad, resistors RA and R5 connected in series in the supply circuit. between condensers C3 and tap S and a con These and other objects, features and aspects denser Cll connected at a point 2 between resistors will be apparent from the following description R4 and R5. of a practical embodiment illustrating the char An ampli?er tube T2 has a cathode k2 con acter of the invention; this description refers to nected to line terminal B, a grid g2 connected to a drawing in which 40 point z of network N2 and an anode a2 connected Fig. 1 is the circuit diagram of a level control to a coupling network N3. installation incorporating the present invention; Network N3 comprises a load resistor R8 in and parallel to a condenser C5 and connecting anode Figs. 2 and 3 are diagrams illustrating the a2 to line terminal A. operation of the circuit according to Fig. 1. 45 A third ampli?er tube T3 has a cathode 703 Fig. 1 shows two line terminals A, B which may connected to line wire A, a grid 93 connected to for example supply 60 cycle alternating current. the tube side of network N3, and a plate a3 con A potentiometer R6 is connected between line nected to line terminal B through relay magnet terminals A and B and may be in series with the M in parallel to a sustaining condenser C6. Mag heater elements hl, h2, 723 of the tubes used in net M may operate a switch Sm which in con the circuit. ventional manner controls for example a signal A double duty electron discharge tube Tl com device ll or a motor that drives apparatus for prises a cathode kl, two anodes at and ad re ?lling tank 5. spectively, and a grid gl which constitutes, with It should be noted that tubes T2 and T3 con kl and at, a conventional triode, whereas kl and 55 duct in different directions and are related to 2,418,020 networks N2 and N3 as follows. The conductivity of T2 depends during the half cycles when line wire A is positive, on the grid-cathode voltage of T2 which again depends on the condition of 4 B is positive, so that magnet M remains deene'r gized. Recapitulating the condition of the circuit while bridge NI is balanced, the triode portion of Tl is then conducting together 'with the diode portion, the grid-cathode voltage of tube T2 is more positive when line terminal A becomes posi certain amount of current, charges during these tive, T2 is conducting, and T3 is non-conducting conducting periods condenser C5 to such a degree with M deenergized. that the charge of C5 will, during the half cycles If now the material 4 in tank 5 rises until when line terminal B is positive, render grid 93 10 probe plates l and 2 become immersed into that su?iciently negative to make T3 non-conductive or at least incapable of energizing magnet M to material the dielectric properties of which differ from those of air, the capacity of condenser Cl operate switch Sm. If now network N2 causes grid g2 to become more negative and hence tube will increase, and ‘bridge NI becomes unbalanced with a voltage appearing between cathode kl and T2 less conductive, condenser C5 will be charged to a lesser degree during the half cycle series grid gl, which renders gl negative when line ter when A is positive, and correspondingly 93 will minal A is positive, so that tube TI is now less be more positive, and T3 more conductive during conductive during these half cycles. the other half cycle series when B is positive, The alternating component passed by condenser with the result that M will be energized when 20 03 becomes under these conditions considerably the cathode-grid potential of tube T2 is com greater than before, since there exists now a paratively more negative. considerable plate voltage change across the tri This arrangement operates as follows: ode portion of Tl during both half cycles where It is assumed that, under normal conditions, as, as pointed out above, appreciable voltage the plate gap 3 of detecting condenser Cl is free 25 change occurred previously only during those half from any agent other than the air therebetween, cycles when tube TI is non-conductive. This and that the bridge network Nl has been so bal considerable voltage change or gradient during anced, by means of adjustable resistor Rl, that the conducting half cycles, together with that there exists no potential di?erence between points during the half cycles with line terminal A neg 0 and p or cathode kl and grid gl. Tube Tl ative, provides a greater voltage across condenser will then carry current in its triode portion with C3. As indicated at V0’ and Vr’ of Fig. 3, this anode at positive, during the half cycles of the higher voltage across C3 which counteracts the supply alternating current when A is positive, as drop in resistor R5 makes more negative the volt indicated in Fig. 2, where V5 is the supply voltage. age Vb’ between tap S and grid g2, decreases the network N2. The plate current of T2 and net work N3 is so selected that tube T2 carrying a The plate potential of the diode portion of tube 35 conductivity of tube T2, and renders grid g3 of tube T3 more positive since condenser C5 fur TI with respect to cathode kl is composed of the nishes now less counterpotential against the drop alternating component of the potential at triode in resistor R8 during the half cycles when line anode at with respect to cathode lcl, as passed terminal B is positive and tube T3 is in condition by condenser C3, and of potential components in troduced into the diode circuit by network l<:l— 40 to conduct. With grid 93 more positive, tube T3 o—Rl—S—-R5-—R4-—ad. During the half cycles becomes more conductive, and magnet M is ener gized, operating whatever device is controlled by when line terminal A is positive and tube Tl switch Sm. conducts, the potential at .r is not subject to By properly dimensioning condenser C5 the much variation. During the other half cycles, when tube TI is non-conductive, the potential at 45 time interval between response of tube T3 and a: and therefore at 1/ changes in accordance with decrease in conductivity of tube T2 can be con the line voltage. The potential at a: with respect to kl is indicated at V0 Of Fig. 2. The poten tial at y is also in?uenced by the voltage drop across Rl, of the general shape of Vs, as ap plied in series with resistors R4 and R5.v The capacity of condenser C3 is preferably chosen to be comparatively large so that no appreciable trolled according to well known principles; hence, by making condenser C5 comparatively large it is easily possible to avoid premature or acciden tal response of relay M, for example due to mo mentary immersion of probe plates l and 2 caused by splashing of liquid. ' It will be noted that the present circuit re‘ voltage drop appears across it; it acts as. a cou sponds only to unidirectional change of the de pling or boosting element and at the same time tecting value, that is tube Tl Will react only to as a blocking element passing to point y voltage change of the bridge voltage, from balance, in variations appearing at point a: but blocking the one direction, namely a change rendering grid gl more negative. In the particular bridge circuit flow of a direct current component between these shown in Fig. 1, this corresponds to an increase points. The resultant of these voltages is recti?ed in 60 in capacity of condenser Cl. If response of the circuit to decreasing capacity is desired, the the diode portion of TI and smoothened into a bridge may be adjusted to be normally unbal steady direct voltage by resistor R4 and con anced, so that decreasing capacity of the de denser CG, as indicated at Vr of Fig. 2. This tecting condenser will balance the bridge. A sim recti?ed voltage between y and S is added to the ilar result can be obtained by interchanging con voltage drop across R5 which is‘ positive when line terminal A is positive and tubes TI and T2 denser Cl and resistor Rl, in which case, how the detecting condenser can not be are conducting, the sum of these voltages con ' ever, stituting the cathode-grid potential of tube T2. It should be understood that the present dis As indicated at Vb of Fig. 2, the bias of grid g2 of that tube is so adjusted by means of slider P closure is for the purpose of illustration only and that this invention includes all modi?cations and S that, with bridge Nl balanced, tube T2 passes equivalents which fall within the scope of the enough current to effect a voltage drop in R8 appended claims. ’ ' ' which, as above described, renders grid g3 of tube T3 sufficiently negative to prevent that tube from becoming conductive during the half cycles when 1. In an electronic control device wherein a grounded. ' . . 5 2,413,020 6 probe impedance of an alternating current bridge network affects the voltage between the control electrode and the cathode of a controlled electron discharge means having at least three electrodes, an uncontrolled rectifying electron discharge connected between said anodes, and a load net work in the anode circuit of said rectifying dis charge means, the voltage across said capacitance and hence across said load network varying with Ll varying conductivity and hence alternating volt means having an anode and a cathode which is age variation in the anode circuit of said con connected to said cathode of said three electrode means, a capacitance connected between said anode and the anode circuit of said three elec— trode means, and a load impedance in the anode circuit of said rectifying discharge means, the trolled discharge means upon unbalance of said bridge network due to change of dielectric mate rial between said probe plates, as compared with the substantially constant voltage variation in the anode circuit of said rectifying discharge voltage across said capacitance and hence across said load impedance varying with varying con ductivity and hence voltage variation in said means. anode circuit of said three electrode discharge means upon unbalance of said network, as com pared with the substantially constant voltage 4. In an electronic control device wherein a detecting impedance of an alternating current bridge network aiiects the voltage between the control electrode and the cathode of an electron discharge means having at least three electrodes, an electron discharge device having two anodes, variation in said anode circuit of said rectifying discharge means. a control grid associated with the ?rst one of said 2. An electronic control device comprising an 2-0 anodes and a cathode common to both anodes, alternating current bridge network including a means associated with said network and said detecting impedance, a controlled electron dis cathode and control element for varying the con charge means having anode, cathode and control ductivity between said cathode and said ?rst electrode, means associated with said network anodeupon variation of said detecting impedance, and said cathode and control element for vary a capacitance connected between the circuits of ing the conductivity of said discharge means said anodes, and a load impedance in the circuit upon variation of said detecting impedance, an of said second anode, the voltage across said uncontrolled rectifying electron discharge means capacitance and hence across said load imped having an anode and a cathode connected to the ance varying with varying conductivity and hence cathode of said controlled discharge means, a ' alternating voltage variation in the circuit of condenser connected between said anodes, and a said ?rst anode upon unbalance of said network, load impedance in the anode circuit of said recti as compared with the substantially constant volt fying discharge means, the volt-age across said age variation in the circuit of said second anode. condenser and hence across said load impedance 5. An electronic control device comprising a varying with varying conductivity and hence al source of alternating current; a controlled circuit ternating voltage variation in the anode circuit including potential apportioning means; a con of said controlled discharge means upon varia trolling circuit including a ?rst electron discharge tion of said detecting impedance, as compared means having anode and cathode connected .to with the substantially constant voltage variation said source and having conductivity control in the anode circuit of said rectifying discharge 40 means, and detecting means associated with said means. control means for varying the conductivity of 3. An electronic level control device comprising an alternating current bridge network having in said discharge means; a second, recti?er, electron one of its arms condenser means including two ?xed plates constituting probes with a gap there between adapted to be penetrated by material whose level is to be detected, a controlled elec tron discharge means having anode, cathode and control electrode, means for applying the output voltage of said bridge between said cathode and said control element, an uncontrolled rectifying electron discharge means having an anode and a cathode connected to the cathode of said controlled discharge means, a capacitance discharge means having a cathode connected to the cathode of said ?rst discharge means and an anode associated with said potential apportioning means of said controlled circuit; and condenser means connected between said two anodes; the charge of said condenser means and hence the potential of said apportioning means of said con trolled circuit varying with the current variation in said controlling circuit and hence with the e?‘ect of said detecting means. WILLIAM F. WOLF'NER, II.