Electronic apparatus for biological research Electronic apparatus for biological research electronicappara00dona Year: 1958 STATIC MECHANOELECTRICAL TRANSDUCERS entirely on the suspension of the moving electrode. In some cases it is possible to attach this electrode directly to the preparation, in which case the loading effect of the transducer can be made negligible. When the trans- ducer is operated through a thread or chain, some form of spring suspension is necessary; the compliance of this spring determines the impedance of the transducer. Torsion wire control spring Operating arm with p
Electronic apparatus for biological research Electronic apparatus for biological research electronicappara00dona Year: 1958 STATIC MECHANOELECTRICAL TRANSDUCERS entirely on the suspension of the moving electrode. In some cases it is possible to attach this electrode directly to the preparation, in which case the loading effect of the transducer can be made negligible. When the trans- ducer is operated through a thread or chain, some form of spring suspension is necessary; the compliance of this spring determines the impedance of the transducer. Torsion wire control spring Operating arm with platinum wire tip Output Perspex trough containing glycerin Energizing voltage lOOV ac. Figure Liquid potentiometer for displacement measurement Two examples of liquid potentiometers will serve to illustrate their possibilities. The first, due to J. A. Popple, is illustrated in Figure An output of 50 V per cm movement can be obtained with an input com- pliance of more than 10'^ cm per dyne (10 cm per g wt). This transducer has been used to study the gill movements of fishes. The second design {Figure ) is due to Dr. D. W. Kennard, and has several novel features. First, a very stiff suspension is used as the transducer is designed for the measure- ment of muscle forces under isometric conditions. Secondly, energiza- tion is used. It is found that, provided the voltage across the electrolyte is low enough ('->-'l V), polarization effects stabilize after about an hour, and that no bubbling occurs. The suspension compliance is about 10''^ cm per dyne (1 fx per g wt), giving a usable response up to about 5 kc/s. A sensitivity of 1 /iV/dyne (ImV per g wt) is obtained. Resistance transducers based on deformation—If a length of wire is subject to stress the resulting elongation and change of area alters its resistance. This principle is used in the resistance strain gauge, which consists of many turns of resistance wire wound on a paper former. In the engi
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