Laboratory Jottings

Radio Record, Volume V, Issue 20, 27 November 1931, Page 30

Laboratory Jottings

Simplex Condensers A NEW line of fixed condensers has been introduced by Standard Telephone and. Cables, and several of these have been tested in our laboratory. The main features about the new condensers are a still greater reduction in size and an improvement in their capabilities to withstand high voltages. Another factor which set

constructors will appreciate is that they are cheaper than their predecessors.’ It will be remembered that Standard Telephones and Cables some time ago introduced a condenser which was considerably smaller than the average fixed condenser on the market. This was made possible by the use of an improved dielectric, and the new Standard being smaller, should find great favour with constructors. Our. tests were for capacity and insulation, and all condensers withstood the testing voltages of a thousand volts d.c. applied from 3 to 5 minutes. and upon testing for capacity showed

no appreciable alteration. A condenser was immersed in water for five hours and again tested, but there was no change in insulation or of capacity. Tested on a.c. to ascertain at what voltage a condenser would actualiy break down, we found that after 750 volts a.c. had been applied for two hours, the insulation failed. This is rather remarkable, as a condenser of this rating should have gone long before this. Our general conclusion is that the "Simplex" Standard Condensérs are entirely satisfactory. They carry our recommendation.

"THE following figures have been taken from the report of the International Telephone Laboratories. They indicate the resistance of the condenser upon delivery and after having been stored at 80 per cent. humidity for four days and for twelve. The figures indicate the state of affairs after 1000 volts d.c. had been applied for 3 minutes :-- , The standard requirements of the Telephone Laboratories for condensers upon delivery are:

Upon Delivery. During 4 days, During 12 days. Megohms M.F. Megohms . M.F. Megohms 2 M.B. wecsees 1.9 8000 1.9 2920 1.9 2846 2 MF. .seeee. 1.9 3000 1.9 2846 1.9 25383 2 MP. wccoces 1.9 3000 1.9 2642 1.9 2533 1 MLR wcccees 0.91 4220 0.94. 4200 0.97 4000 0.5 M.B. .ecceee 0.50 6330 0.52 86300 0.52 6000 O.1 M.F. ..ceeee =-s-COO..09 7600 0.09 7000 0.09 8600

2 MF min 100 megohm 1 " " 200 " 0.5 "? " 400 " 01 ,, " 2000 "