Gamry Reference 3000 Operator's Manual page 74

Chapter 9 -- Measurement of Small Current Signals--Measurement System Model and Physical Limitations
In Figure 9-1:
E Is an ideal signal source
s
Z Is the unknown cell impedance
cell
I Is the "real" cell current
cell
R Is the current measurement circuit's current measurement resistance
m
R Is an unwanted resistance across the cell
shunt
C Is an unwanted capacitance across the cell
shunt
C Is the current measurement circuit's stray input capacitance
in
R Is the current measurement circuit's stray input resistance
in
I Is the measurement circuit's input current
in
In the ideal current measurement circuit R
flows through R .
m
With an ideal cell and voltage source, R
current measurement circuit is due to Z
The voltage developed across R
can use Kirchoff's and Ohms law to calculate Z
Z = E
cell
is infinite while C
in
is infinite and C
shunt
.
cell
is measured by the meter as V
m
:
cell
* R / V
s m m
Equivalent Measurement Circuit
R shunt
C shunt
R in
and I are zero. All of the cell current, I
in in
is zero. All the current flowing into the
shunt
. Given the idealities discussed above, one
m
Figure 9-1
Icell
C in
9 - 2
cell
Rm
,