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General Radio 1688 LC Digibridge
Elgin, IL
General Radio


Electronic Test Equipment
Condition info:
Subcategory 2:


The General Radio 1688, LC Digibridge, that is a digital impedance meter and limit comparator embodying use of a microprocessor and other LSI circuitry to provide high accuracy, convenience, speed, and reliablility at low cost. Internal bias is provided and both test frequency and voltage are selectable.
Measurement Parameters and modes are series or parallel L and Q, series or parallel C and D, series C and ESR, or parallel C and parallel equivalent R. Continuous-repetitive, single, or averaged (set of 10) measurements; start button initiates single or averaged measurements. Keyboard selection of these and all measurement conditions.
Main Displays are: in MEASURE FUNCTION (3 selections): Value display is LED-type numerical readout with automatically positioned decimal points and illumination of units; five digits for LC (99999) and simultaneously four digits for D, Q, ESR (9999). Delta-percent display is percentage difference between LC measurement and previously stored nominal value. Bin number display shows the bin assignment of the measured device. (Refer to "sorting" below.) In ENTER FUNCTION: Display shows comparator bin limits, nominal values and test frequency.
Measurement Rates: 0.5, 2, 3, and 8 measurements/second. Keyboard selections are: extended accuracy, slow, medium, fast.
Test Frequencies: Keyboard selection by entering any desired frequency: the Digibridge responds by selecting nearest one of 254 frequencies between 234.37 Hz and 20 kHz, inclusive. Selected value is automatically displayed. Available frequencies are: f = (60/n), where n is an integer that satisfies 3