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Electrical ResettingDevices for the DunlapChronoscopeErwin A. EsperPublished online: 06 Jul 2010.

To cite this article: Erwin A. Esper (1932) Electrical Resetting Devices for theDunlap Chronoscope, The Journal of General Psychology, 6:2, 478-480, DOI:10.1080/00221309.1932.9711893

To link to this article: http://dx.doi.org/10.1080/00221309.1932.9711893

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475 JOURNAL OF GENERAL PSYCHOLOGY

Of course, such a procedure presumes the use of a n amplifier having stable characteristics.

REFERESCES

1. DAKROW, C. W. Continuous quantitative records in s tandard units by

2. . Uniform current fo r continuous s tandard unit resistance the Wheats tone bridge method. J . Grri. Psyclrol., 1930, 4, 418-420.

records. J . Gcn. Psyclrol., 1932, 6, 471473.

Brhnvior Rcsccircli Furid Chicago, Illinois

ELECTKICAL R E S E T T I N G DEVICES FOR T H E DUNLAP C B R O N O S C O P E

ERWIN A. EWER

W h e n the Dunlap chronoscope is used for measuring a long series of reaction times, the manual restoring of the hands to zero af ter each meas- urement results in undesirable delays and irregularities in the succession of stimulus presentations, and perhaps also in occasional inaccuracies in the resetting. I n Figures 1 and 2 a r e shown two devices whereby the chrono- scope may be reset to zero electrically by a pressure on a key.

Since this model lacks a revolution counter dial, only the la rge hand needs t o he reset. T h e lever S.4-CL, of No. 11 music wire , passes through a n in- sulated bear ing in the clamp block. T h e a r m C L dips into a small mercury cup. T h e clamp block is of brass, the f ront j a w bevelled to clear the clock- hand, and the rear j a w fitted with a milled set-screw wherehy the clamp can be fastened on the circumference of the dial. T h e brass bear ing f o r the lever is contained in a bakelite piece screwed to the top of the clamp block, and a bakelite hracket screwed to the side carr ies the small brass plate on which a r e mounted the mercury cup and its binding post. T h e horizontal shaf t which passes through the bearing, and whose f o r w a r d end is bent to form the striker a r m ( S , 4 ) , is 1%” in length; the horizontal a r m whose bent end dips into the mercury cup is 13/16” in length.

T h e device is used in conjunction with a 3-leaf key similar to the Dunlap master key, but the upper and lower leaf circuits a r e interchanged as com- pared with the stimulus-reaction a r rangement ; that is, the upper leaf is in the posterior magnet circuit and the lower leaf in the anterior magnet circuit. T h e resetting device is connected by its binding posts in series with the posterior magnet. I-Ience, when the dial hand is a t any position other than zero, a pressure on the key closes the circuits, first, through the posterior magnet, and, secondly, through the anterior magnet ; the hand

Figure 1 shows a restoring device for the Model I11 chronoscope.

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APPARATUS 479

FIGURE 1

revolves until it strikes the striker arm, breaking the posterior magnet circuit a t the mercury cup. By means of the clamp block the striker a rm may be empirically adjusted to such a horizontal and vertical position a s to stop the hand exactly at zero. T h e above wiring is independent of and in addition to the stimulus-reaction circuits, and in no w a y changes the operation of these circuits. T h e lightness of the wire lever obviates the possibility of ja r r ing sufficient to cause armature “hunting.” On the other hand, I have found that if gold or silver contacts a r e used instead of the mercury cup, the motor vibration j a r s such contacts very slightly, but suffi- ciently to cause clutch slippage and consequent armature “hunting.” If it is found that the wire contact rides on the surface of the mercury instead of dipping into it, this same trouble will be experienced, and it will be necessary to fasten an adjustable weight, e.g., in the form of a few coils of light steel spring, to the mercury cup lever arm. I t is also advantageous to sharpen the contact wire.

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J O U R N A L OF G E N E R A L I’SYCHOLOGY

FIGURE 2

Figure 2 shows a reset t ing device l o r t he Mode l I1 chronoscope, whereby both the l a r g e d i a l hand a n d the revolution counter m a y be restored to zero. O v e r the knurled knob h-h‘, which is furnished with this model fo r manua l resett ing, is d r iven the fiber r i n g FR of 3/16” thickness, bea r ing a small h ra s s i inger. :Is t he revolution counter rotates, this finger l if ts t he lever C L , therehy b reak ing a contact a t CS. T h e Icver C L is 3 : 4 ” i n l eng th ; i ts bea r ing (no t shown) is ca r r i ed by a fiber post screwed to t h e chronoscope base. T h e contact s c rew CS permits of adjustrncnt so tha t t he contact will be broken a t t he exact instant when both h a n d s a r r i v e a t zero. P l a t inum or gold contacts c a n be used in this case because the g rea t e r power ava i l ab le permits of heav ie r we igh t ing of the lever. T h e w i r i n g is the s a m e as f o r the previously described device.

Both of t he above devices h a v e been in intensive use ove r per iods of several months, a n d h a v e been found to faci l i ta te the smooth presentation of reaction series.

Uniwcrsity of W n s h i n g t o n Seattle, W a s l r i n g f o n

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