Block Diagram - Keithley SourceMeter 2400 User Manual

®
2400 Series SourceMeter User's Manual

Block diagram

A block diagram of the contact check circuitry is shown in
sor sends a contact check pulse that is amplified to drive the primaries of four transform-
ers. The secondaries of transformers T1 through T3 drive a force/sense contact pair for HI,
LO, and GUARD. (HI Force and LO Force are switched through S1 and S2.) The trans-
formers provide isolation among the inputs. Capacitors C1 through C3 in the secondaries
provide a high resistance DC path but low resistance AC path between the force and sense
leads. Transformer T4 drives the trip point resistor(s), R
DUT connections exceeds the value of R
and the microprocessor is notified. Note that the trip point resistance (R
changed by closing either switch S3 or S4, resulting in 2Ω, 15Ω, or 50Ω threshold resis-
tance values.
Figure F-2
Contact check block diagram
To
Microprocessor
Signal Comparitors
Computer Interface
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SET
it is considered an OPEN LEAD condition
,
SET
T1
Pulse Amplifier
Timing Generator
T2
T3
T4
Contact Check Function F-3
Figure F-2. The microproces-
. If the resistance in any of the
) can be
SET
S1
HI Force
C1
HI Sense
S2
LO Force
C2
LO Sense
Guard Force
C3
Guard Sense
C4
R R R
setA
set setB
50Ω 22Ω 2.1Ω
S3
S4