ANALYTICAL CHEMISTRY
982 (4) Honig, R. E., Science, 104,27 (1946).
( 6 ) Matchett, J. R., and Levine, J., IND.ENQ.CHEM.,ANAL.ED.,15, 296 (1943). (6)Quackenbush, F.W., and Steenbock, H., Zbid., 15,468 (1943). ( 7 ) Sheppard, C. W., and Burton, V. L., J . Am. Chem. Soc., 68,1636 (1946). (8) Sheppard, C. W., and Whitehead, W. L., Bull. Am. Assoc. PB trolevrn Geol., 30,32 (1946).
H. J., Matchett, J. R., end Levine, J., IND. ENO. CHEM.,ANAL.ED., 16,629(1944).
(9) Wollner,
RECEIVEDOctober 6, 1947. Contribution from American Petroleum Institute Research Projeot 43C loosted s t *he Massachusetts Institute o! Technology; W. L. Whitehead, duwtor; Clark Goodman, physical director.
Simple Electronic Reflux Ratio Timer HERBERT E. FISHER Shawinigan Chemicals, Ltd., Shawinigan Fulls, Quebec, Canadn
N T H E course of the past few years, the increasing popularity
this time, analogous to Ry,). As the negative voltage, stored b? CI, on the control grid of VI biases the beam power section to cutoff, Ry1 drops out and remains open until the charge on C1 has leaked off through R1R2. The time interval during which Ryl is energized is controlled by the setting of R1 and, with the constants given, ma>-be varied over a period of 4 to 60 seconds When the negative charge has leaked off the control grid of VL, Ryl pulls in once more and the cycle is repeated. Vl thus delivers a repetitive pulse (through contacts Sl of Ry,) a t a constant, controllable rate. The action of V2, triggered by the pulse from VI,is strictly analo gous, except that theoutput circuit doesnot pulse The constants given in theschematic diagram re sult in a deliverv period of 1to 5 seconds, variable b r Rs. VI and Vg are interlocked through contacts St of Ry,to prevent Vi from pulsing unless V2 has completed its timing cycle. The output of ITp(through Ry2)is delivered to X1X2,an ordinary duplex receptacle with one of the connecting straps divided into two, which enables the timer to operate directly a reflux dividing head activated by two alternately energized magnets. The more common type of single solenoid head may be activated from rece tacle Xt. 1 The single receptacle, which may be connected a t will to either timing interval by the single-pole double-throw sxitch, 8 7 , serves the 3 purpose of initial calibration, or accurate resetting of controls R1 and R3 when an electric stop AC clock is connected to it. Switch Sg may be opened Figure 1. Schematic Diagram to de-energize the output circuit without shutting off the timer. Pilot lights P1 and Pz indiR t . 3-meeohm carbon DO tentiometer Ruz Double-vole double-throw re_ (SsSd. . R;. 250,050-ohm, O.5-6att resistor lay, 1000- 60 4000-ohm coil cate which of the output circuits is connected, VI Vn. 117 L7/M7-GT bubes RI. 1-megohm carbon potentiometer and map be used for stopwatch timing in CaliR4. 50,000-ohm, 0.5-watt resistor Sa,’Sa. Single-pole single-throw toggle brating or checking the device. CI. 4-mfd. paper condenser, 400-volt switches
of magnetically operated heads for distilling columns (Oldershaw, D u Pont, Piros-Glover) has made a flexible, low-cost timer desirable. Earlier controls based on single synchronous clock motors were reliable and cheap, but suffered from the restrictions imposed by simple proportioning of a fixed total period. More elaborate double synchronous clock motors eliminated this difficulty, but required considerable maintenance, usually had a fixed “on” period, and rwre relatively expensive.
3,
Ci. 2 mfd. paper Condenser, 400-volt CI, Cd. 8-mfd. electrolytic condensers, 250volt R y l (5152). Double-pole double-throw relay, 1000- to 4000-ohm coil
S I . Single-pole double-throw toggle switch XIXZ. Duplex receptacle (see text) XI. Single receptacle Pi, P2. 110-volt Ss pllot light@
Recently Thacker and \17alker ( 4 ) described ail electronic timer which met most of the requirements, but had the disadvantage of rather specialized, difficultly obtainable parts. The two-tube electronic timer described below is reliable and flexible and is easily constructed a t very low cost (under $20). The circuit is based on the well-known condenser discharge principle, which has been used, in various forms, for pump control ( 1 , S),spectrographic exposure control (a), and time delay relays. I t consists of two interlocked timing units, one for “off’ or reflux timing, the other for “on” or delivery timing. Both periods may be varied over a wide range by selection of proper resistance and capacitance values. The constants given in Figure 1 serve only as a guide, and may be changed to suit the application of the device. The operation of the timer may be easily understood by considering separately the action of each tube. Khen switch S6 is closed, tube Vl warms up and the beam power section acts as a self-rectifying amplifier, drawing current through relay Ryl and closing its contacts, SI and Sz. The diode rectifier section of VI then applies a negative bias to the control grid of VI beam tetrode through contacts S2 of Ryl and Sa of Ry2 (the latter has closed by
The timer, as described above. has been in u ~ e in the Research Laboratories ’ of Shawinigan Chemicals for the past year, much of the time on 24-hour, 5.5-day-week service. No maintenance or tube replacement has been required during this period. Constancy of timing over 24-hour periods has been better than 1%. ACKNOWLEDGMENTS
The author wishes to acknowledge gratefully the encouragement of K. G. Blaikie, director of the Research Laboratories, Shawinigan Chemicals, Ltd., and to thank Shawinigan Chemicals, r,td., for permission to publish this work. LITERATURE CITED (1, Bechthold, I. C.. ISD. ESG. CHEM., ANAL.ED.,14,429(1942) 12) Gentr5, C. H.R., Newson, D., and Rushman, D. F., J . SOC.C h m
Ind.,66,323 (1947). (3) Taylor, J. I(.and Reid, J. G., IND.ENGCHEM.,ANAL.ED.,18
79 (1946). (4) Thacker. G. O.,and Walker. B. P., J. SOC.Chem. I d . , 65 2.59 (1946).
RECEIYED January 28, 1948
