. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. TIMERS, COUNTERS AND RATE MEASUREMENT {Figure ). The total is indicated digitally in a small window up to a maximum of 9,999. These devices are electromagnetic and have coils wound for a variety of impedances; some are only of a few ohms and are not of much use in conjunction with electronic apparatus except via a relay. There is, however, a 500 ohm model which operates on a current of 100 mA, suitable for inclusion in the anode circuit of a small thyratron, and a 2,300 ohm type which
. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. TIMERS, COUNTERS AND RATE MEASUREMENT {Figure ). The total is indicated digitally in a small window up to a maximum of 9,999. These devices are electromagnetic and have coils wound for a variety of impedances; some are only of a few ohms and are not of much use in conjunction with electronic apparatus except via a relay. There is, however, a 500 ohm model which operates on a current of 100 mA, suitable for inclusion in the anode circuit of a small thyratron, and a 2,300 ohm type which is operated by 30 mA, appropriate for control by a power valve. Drop counters Drops are counted either conductimetrically or photoelectrically. In the former method drops are used to bridge a pair of electrodes enabling a current to flow which causes, directly or indirectly, the operation of the indicating device. A simple direct system, intended for kymograph marking, is shown in Figure , in which the indicator is a high-resistance post Cl o a o Q. O O =s o4H a o. 1111 Inter-electrode resistance 120V. HT batteries Figure Amplifier- output "V—r y Time Figure office relay with a light pointer attached to the clapper. A similar arrange- ment, but mains driven, has been demonstrated by Bernstein and Betts^. The difficulty with simple counters such as these is the damage done by electrolysis to the body fluid being measured, rendering it unsuitable for recirculation or analysis. In addition, mechanical obstruction arises in the counting cell due to the generation of foam by electrolysed gases. More sophisticated counters employ a valve or thyratron to control the indicator; in this way the current passing through the fluid can be made much smaller. The mechanical design of drop-counter cells is quite difficult. It must be realized that the device has to accept fluids of a wide range of viscosities and delivery rates. Typically, trouble may be experienced from
Size: 1816px × 1375px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionameri, bookcollectionbiodiversity
