A CONVENIENT METHOD of MOUNTING CONDUCTIVITY and POTENTIOMETER SETUPS PHILIP E. HATFIELD AND A. STRICKLER Evansville College, Evansville, Indiana
E ARE interested, in our laboratory, in the 19 inches by 12 inches is mounted on the front of the development of equipment that is convenient, rack, 33 inches from the bottom, to hold the slide compact, and portable because, like most small wire, resistance box, and key. The oscillator is patterned after that of Saylor and laboratories, i t is often difficult to find sufficient space in which to make semipermanent setups. We are also Debruyne (2), and coninterested in the adaptation of amateur radio equip- tains a stage of amplificament and methods to physical chemical technic. In tion to increase its output this connection we recently (1) presented a portable and a t the same time isothermostat with a modified electron tube control. late it from the bridge. However, certain changes This paper describes a method of mounting conhave been made. A pair : of type 27 tubes have been d u c t i v i t y a n d electrosubstituted for the type motive force equipment and gives some new sug71a's so that alternating current can be used on gestions regarding connections and endpoint control. the filaments. A superhet T h e equipment is intermediate frequency . . .. . . . transformer is used for .,-, mounted in a so-called the oscillator coil. In "standard relay rack." addition, the difficulty This is not, however, the of matching the oscillator all-steel rack used in the to a student-type slide communications industry wire has been overcome by but is an inexpensive one constructed of wood. The using as an output transformer one which was rerack is 60 inches high and moved from a dynamic 19 inches wide, made of speaker. This transformer 1-inch pine. The panels is designed to match the are 19inches by @/=inches, plate of a type 45 tube and are made of '/,-inch to a 30-ohm voice coil. plywood. The rack is The oscillator and its ammounted on a wood platplifier are shielded by copform which is in turn supFIGURE 2 per cans. A grounding ported by rubber casters. FIGURE1 system patterned after The entire unit is painted that o f Jones and Josephs (3) is used on the oscillator. black (Figures 1-4). The bottom panel unit ( A ) contains the power sup- A 100,000-ohm potentiometer is connected aaoss the plies for the oscillator and the balance indicator. The output of the oscillator and the sliding arm connected third panel unit (C) contains the oscillator and its to ground. The output of the oscillator is fed to the amplifier. The fifth panel unit (E) carries the termi- terminal board through shielded, grounded cable. The terminal board is arranged so that the slide nal board for the conductivity bridge and the E.M.F. setup. The sixth panel unit ( F ) contains the balance wire, resistance box, and key may he placed on the indicator. The seventh panel unit (G) carries the shelf which is located just below it. These are conoperating instructions. The second and fourth panels nectedinto the circuit withshort wire jumpers. This al(B and D) have been left empty to accommodate addi- lows these units to be easily removed for storage, or tional equipment which can be added later. A shelf for use in another place. The terminal board panel i80
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also carries a telephone jack into which can be plugged either a pair of head-phones or a patch cord from the visual balance indicator to indicate bridge balance.
the balance point of the bridge has been reached. A pointer type galvanometer with a shunt is used for the meter. A patch cord is connected to the input of the
FIGURE 4 Photograph by R . A . Neville FIGURE 3 Photograph by R . A . Neville
A Leeds and Northrup Student Slide Wire is used:in the setup, but any similar type can be used. The balance indicator is visual one described by Garman (4) and uses a type 75 tube with a meter in the plate circuit which shows a maximum reading when
balance indicator so that it can be plugged into the telephone jack on the terminal hoard. In connection with visual balance indicators some work was done with the type 6E5 "Magic Eye" tuhe in an effort to use it for
