Keithley 199 Instruction Manual page 117

PRINCIPLES OF OPERATION
R Ref HI To Q35 of
' Multiplexer
Reference
Resistors
R Ref LO To U24C of
(3OW
' Multiplexer
n Ref LO
(3OOQ 3kQ)
> To U24D of
Multiplexer
Input
\ HI
/
R Ref LO
To 034 of
(3OOkQ 3OOMR) ' Multiplexer
-->->
To Q30 of Multiplexer
n Sense HI
Rx
R Sense LO
-->->
To U24B of Multi&xer
Input
q
LO
R
R, =
FW l
(Vl2 Sense HI - Vn Sense LO)
Vn Ref HI . V.Q Ref LO
Figure 5-3. Resistance Measurement Simplified Circuitry
5-5