MEASURING THE CAPACITY OF FIXED CONDENSERS

Radio Record, Volume I, Issue 22, 16 December 1927, Page 12

MEASURING THE CAPACITY OF FIXED CONDENSERS

A SIMPLE METHOD

This is a method of obtaining a fairly accurate’ iden of the capacity. of | a fixed condenser Within about five per cent. of the total. ‘The system is best adapted to condensers larger than 0.0005 m.f.d. As standards to work by, the average amateur will find a .001 and a 0005 .of good make sufficient for his purpose. The diagram shows the hook-up, B is a buzzer of some kind, A the battery to supply current, CD is a yard or a metre of bare resistance wire stretched alongside a measure of the same length. Cl is the ‘standard condenser and C2 the condeuser to be tested. Connected’

between these is ‘one side of a pair of ‘phones, the cther side .X being slid along tie resistance wire when testing. ‘he buzzer circuit is through the resistance wire, so the latter must be thick enough. to allow a workable cuti

reut to pass, so a gafige irom 26 to 80’s s.w.g. will serve. . The buzzer ghould be plaved so that its send does not interfere with that heard in the *phounes. In operation, with the buzzer working, the ’phone tip is* slid" backwards and forwards until the ‘point X is found where the buzzer note is faintest or practically disappears. This. can generally be located within half an inch. When this has been done, measure the two distances EX and. DX, then the capacity of C2 is capacity .of C1 multiplied by EX and divided by DX. This method has been tested and ‘found useful, but naturally depends to some extent upon the way the circuit is laid out and the care with which the testing is done. . No test the accuracy of your Clircuit, place the .001 ou one side and the .0005 on the other side, and. see how near the trial calculates out. Them reverse positions and test again.