2-8 Connections Model 6485 and 6487 User’s Manual
Figure 2-8
Basic Model 6487 ohms connections
HI
LO
DUT
INPUT*
LO
HI
V-SOURCE OUTPUT
6487
* Maximum Continuous Input: 505V Peak
Noise and safety shields
Figure 2-9 shows typical measurement shielding. In (A), a noise shield is used to prevent
unwanted signals from being induced on the picoammeter input.
Amps measurements
below 1μA may benefit from effective shielding. Typically, the noise shield is connected
to picoammeter input LO. Additionally, Figure 2-9(B) shows an added safety shield con-
nected to earth ground and Model 6487 chassis. Th
is type of shielding should be used
whenever hazardous voltages will be present in the test circuit.
WARNING The maximum safe voltage b
etween picoammeter LO and chassis
ground (common mode voltage) is 505V peak. The Model 6487 does not
internally limit the LO-to-chassis voltage. Exceeding 505V can create a
shock hazard.
If it is possible for the DUT or external supply to
present more than
505V to the input HI, it is imperative that the connection between
input LO and the external voltage source be sufficiently low imped-
ance and capable of carrying the short-circuit
current of the source, in
order that the LO not exceed 505V.
CAUTION The
LO to chassis breakdown voltage is 505V. Exceeding this voltage
may cause damage to the instrument.
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