โ Scribed by Joseph Razek
No coin nor oath required. For personal study only.
A simple means for combining a small direct voltage with an alternating carrier is described. This consists of connecting the direct voltage in series with an alternating voltage of the same order of magnitude. The two are then passed through a copper oxide rectifier which suppresses one part of the cycle. The degree of suppression depends upon the magnitude of the direct voltage. The resulting fluctuating voltage can be amplified to any desired degree in a conventional amplifier.
The theory for the simple case of pure resistance is worked out, with an example. The solution of the more general case with inductances is indicated.
The practical circuit which has been used for the amplification of therrnocouple currents, and as a galvanometer power multiplier, is shown.
The problem of amplifying small alternating voltages presents no difficulty, the usual type of transformer or resistance coupled amplifier proving generally satisfactory. The amplification of small direct voltages, however, is considerably more difficult, especially when the source of the voltage has a low internal resistance. Such voltages are met with in the case of thermocouples and similar devices. The feeble power output available requires the use of delicate SUS-(Note.--The Franklin Institute is not responsible for the statements and opinions advanced by contributors to the JOURNAL.
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