QuadTech 1865, Инструкция по эксплуатации, Страница: 32 / 87

Page 32 of 87 Operation
A three-wire guarded connection is necessary to measure resistance between two points
in the presence of resistance from each of these points to a third point. Refer to
paragraph 3.6 for a discussion of guarded measurements. The guarded measurement may
require different grounding techniques depending on the expected impedance of the
DUT.
DUT
+ Unknown and - Unknown are connected to DUT
+ Unknown shorted to GND
DUT
DUT Ungrounded DUT Grounded
GUARD to DUT Guard Point
OR
GUARD shorted to GND
+ -
GRD GND
+ -
GRD GND
a) b)
Figure 2-4: Three-Wire Guarded Connection (Grounded or Ungrounded)
2.5 Measurement Procedure
2.5.1 General
There are two basic measurement modes of operation, auto and manual. In the automatic
mode the test cycle is sequenced automatically through four phases, charge, dwell,
measure and discharge in accordance with user programmable times. This is the
preferred measurement mode, especially when the approximate resistance value is
unknown, since the 1865 instrument employs an auto ranging technique. The automatic
mode would generally be used in a production environment where measurements are
repetitive and setup conditions have been previously established. For the sake of
reducing measurement time, when making repetitive measurements, a particular range
may be locked in, in place of auto ranging.