General Radio 1688 Precision LC Digibridge

General Radio 1688
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Measurement Parameters and Modes: 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: 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.)  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 < n < 256, and f is expressed in kHz.


Ranges of Measurement at 1 kHz
Parameter Minimum Basic Ranges Maximum
L .00001 mH 1.0 mH to 64 H 9999.9 H
C (with D) 00.001 pF 400 pF to 25 µF 9999.9 µF
C (with ESR) .00001 nF 0.4 nF to 25 µF 9999.9 µF
D% (of LC) 0.0001% (fully automatic) 99999%
Q (with L) .0001 (fully automatic) 999.9
D (with C) .0001 (fully automatic) 999.9
D (ext acc) 0001 ppm (fully automatic) 9999 ppm
ESR (with C) .0001W (fully automatic) 9999 kW

Accuracy: BASIC (not including range extensions): For L, ±.04%; C, ±.02%; Q, ±.0002 [1 + (1 + Q)Q]; D, ± 100 ppm (for D < 9999 ppm); ESR, ±.02% ± 1 count.

Applied Voltage: HIGH: 1.0 V rms, open ckt.  LOW: 0.25 V rms, open ckt.

Ranges: Automatic ranging for best accuracy.

DUT Connection: 4-terminal (Kelvin) at built-in test fixture for radial-lead or axial-lead parts.

Zeroing and Recalibration: "Zero" capacitance of test fixture, cable, etc. is stored at keyboard command and automatically eliminated from DUT measured values.

Bias: Internal voltage source -2 V ± 10%, on-off switch.

Sorting: Limit comparator sorts vs a Q D ESR limit and up to 8 pairs of LC limits into 10 bins.  GO/NO-GO is indicated.