. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. POWER PACKS STABILIZED AC MAINS SUPPLIES As an alternative to stabilizing separately EHT, HT and heater supplies it may be worth considering stabilizing the supply mains itself; that is, to draw all one's power supplies from a single stabiUzing device which is fed with unstabilized National Grid power. Stabilized is in any case useful for supplying experimental apparatus of a non-electronic nature, such as light sources. There are a number of commercial units which do this, and d
. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. POWER PACKS STABILIZED AC MAINS SUPPLIES As an alternative to stabilizing separately EHT, HT and heater supplies it may be worth considering stabilizing the supply mains itself; that is, to draw all one's power supplies from a single stabiUzing device which is fed with unstabilized National Grid power. Stabilized is in any case useful for supplying experimental apparatus of a non-electronic nature, such as light sources. There are a number of commercial units which do this, and designs have been published from time to time which are suitable for making up. There are various methods of approach, but all—apart from the constant voltage transformer—are the same in principle: a sensing device detects discrepancies between the actual output voltage and that required, and causes a regulator to correct them—at least partially. Thus in a device due to Ackland^^ the output voltage is bridge-rectified and compared with that existing across a voltage reference tube. The difference is used to actuate a sensitive relay, which—via other relays—controls a motor-driven variac transformer. Such a device is clearly capable of stabilizing large powers, but the rate of response to a sudden change in output would not be very rapid; Ackland claims a correction rate of 8 V per second. A much faster type of stabilizer is due to Benson and Seaman^^. Here a saturated diode is the sensing unit; the diode output is amplified by a valve whose anode current is used to vary the saturation of part of the core of an auto transformer, so that its effective step-up ratio is altered. The response time is I second. STABILIZED-CURRENT POWER SUPPLIES It happens occasionally that a constant current, rather than constant voltage, power supply is required; for example, in the production of a stable mag- netic field by a coil whose temperature, and hence resistance, is subject to
Size: 2236px × 1118px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionameri, bookcollectionbiodiversity
