Current 11ETMA standards call for the measurement of electrolytic capacitors at 120 cycles. As a result, a number of our customers have requested modification of the Type 1611-A Capacitance Test Bridge to permit measurements at this frequency.
The inclusion of a 120-cycle source for use over the entire capacitance range of this bridge would require substantial and expensive alterations. Relatively minor and inexpensive changes, however, make possible the use of an ex-
Type ternal 120-cycle source for measurements with the upper four multipliers of the bridge. These multipliers cover the range from ljuf to 11,000 ni, and are thus appropriate for electrolytic capacitors.
As indicated in the accompanying schematic diagram, the 120-cycle measuring voltage is applied in series with the external d-c polarizing voltage normally required for electrolytic capacitor testing. Since the d-c supply is grounded, the test voltage must be supplied through an isolation transformer, which can also serve to match the low impedance of the bridge (from a few ohms to a few thousand ohms) to the 120-cycle source.
Tuning of the detector to 120 cycles is provided, as is a jack to permit connection of a resonant circuit externally, for measurements at frequencies other than (»0 cycles or 120 cycles.
The dissipation factor range is directly proportional to the test frequency; thus at 120 cycles the range of the bridge becomes 0% to 120%. The dissipation factor accuracy is + (2% of dial reading
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