Model 6517B Electrometer Reference Manual Section 5: Measurement options
6517B-901-01 Rev. C / August 2015 5-9
Preamp out
The PREAMP OUT of the Model 6517B follows the signal amplitude applied to the INPUT terminal.
Some possible uses for the inverting PREAMP OUT include buffering of the input signal, as well as
for guarding in the volts mode. Connections and equivalent circuits for the preamp output are shown
in the figures below. Full-range outputs for various functions and ranges are listed in table below.
Since the PREAMP OUT signal is not corrected during calibration, gain error of up to 15 percent may
appear at this output, depending on function and range selection. For all volts ranges, PREAMP
OUTPUT accuracy is typically 10 ppm.
High voltage may be present between the PREAMP OUT and COMMON terminals depending
on the input signal.
Connecting PREAMP OUT, COMMON, or 2 V ANALOG OUTPUT to earth while floating input
may damage the instrument.
The PREAMP OUTPUT accuracy is uncalibrated.
Note that the PREAMP OUT output resistance is 1 . The output resistance appears between Input
Low and Analog Output Low to keep the resistor out of the loop when using external feedback
elements. To keep loading errors under 0.1 %, the device connected to the PREAMP OUT should
have a minimum input impedance of 100 k.
To prevent damage to the Model 6517B, do not connect a device to PREAMP OUT that draws more
than ±10 0 µA. For example, at 200 V, the impedance connected to PREAMP OUT must be at least
2 M (200 V / 100 µA = 2 M).
Full-range PREAMP OUT values
Function* Range
Full-range
value
Volts
Amps
Coulombs
2 V
20 V
200 V
2 nA, 2 µA, 2 mA
20 pA, 20 nA, 20 µA, 20 mA
200 pA, 200 nA, 200 µA
2 nC, 20 nC, 200 nC
2 µC
2 V
20 V
200 V
2 V
20 V
200 V
20 V
200 V
*PREAMP OUT value for the Ohms function corresponds to the value for the Amps
range that is being used to make the measurement.
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