Preamp Out - Keithley 6512 Instruction Manual

OFF
V, Ω GUARD
INPUT FROM
PREAMP
Figure 2-13
Typical 2V analog output connections

2.8.2 Preamp out

The PREAMP OUT of the Model 6512 follows the signal am-
plitude applied to the INPUT terminal. Some possible uses for
PREAMP OUT include buffering of the input signal, as well as
for guarding in the volts and ohms modes. Connections and
equivalent circuits for the preamp output are shown in Figure 2-
14. Full-range outputs for various functions and ranges are list-
ed in Table 2-7. Since the PREAMP OUT signal is not correct-
ed during calibration, gain errors of up to 3% may appear at this
output, depending on function and range selection. For all volts
ranges, PREAMP OUTPUT accuracy is typically 5ppm.
WARNING
High voltage may be present between the
PREAMP OUT and COM terminals de-
pending on the input signal (see Table 2-
INPUT
COM
2V ANALOG OUT
ON
MODEL 6512
R F = 2MΩ (X10)
200kΩ (X1)
20kΩ (X0.1)
2kΩ (X0.01)
200kΩ
S
MODEL 6512
LO
HI
MODEL 1683
TEST LEAD KIT
(EXAMPLE: CHART RECORDER)
A. CONNECTIONS
10kΩ
2V ANALOG OUTPUT
100Ω
COM
S
B. EQUIVALENT CIRCUIT
7). Open-circuit voltage of 300V is present
at PREAMP OUT in the ohms function.
Connecting PREAMP OUT, COM, or 2V
ANALOG OUTPUT to earth while float-
ing input may damage the instrument.
Note that the PREAMP OUT output resistance is 100 Ω . 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 100k Ω .
MEASURING DEVICE
R L = INPUT RESISTANCE OF
MEASURING DEVICE
CAUTION
Operation
2-19