Keithley 616 Instruction Manual page 28

THEORY OF OPERATION
>--1
Coulombmeter Operation.
In the COULOMB mode, a range capacitor
25764E) .
(ClGl through elll) is connected between input HI
The charge-to-vo ltage conversion 1s
and GUARD.
determined by the following relationship ;
1
E e = ii dt
e
e
e E
� voltage developed
= range capacitor
Q
= stored charge
h. Ohmmeter Operation.
In the " OHMS " mode , a current source is
25764E ) .
connected into the electrometer circuitry.
voltage sensitivity is selected as in VOLT S opera­
tion. The current source is composed of a voltage
source and a series (RANGE) resistor.
resistor is sel�cted in decade steps in the OHMS
position (resistors RID5 through RIll) .
age source is provided by dividing down from a ±12
volt reference supply.
internal calibration adjustment .
R x
24
C
Coulombmeter Configuration - FAST Mode .
FIGURE 2 7 .
(Refer to schematic
g
=
e
acrOBS C
(Refer to schematic
The
The series
The volt­
Potentiometer Rll4 is an
I - ..!...
- .
,
, ,
,
FIGURE 2 8 .
Ohmmeter Configuration - NORMAL Mode .
+
TABLE 4-4.
Ohmmeter Divider Network
Ohms
R
Total
5
10 n
12K 1 . 010
6
10 n 12K 1 . 000Kn
n
7
1.
10 12K OOOIm
8
10
n 12K 1 . {)001<!l
9
ooom
10 n 12K
1.
IO
ooom
10 n
12K 1.
11
ooom
lO n 12K 1.
12
10 n
12K 100
The current developed by the ohmmeter circuit is
determined as followa :
�
E = 12 R 1 /(R l +R 2 )
I =
where I = current in amperes
E
� voltage as in Table 4 -4 .
R range resistor (RID5 through RIll) .
=
+
MODEL 616
1
Vo I dt
R E
2
m
10. 990Kn 1 . 01 V
11. 000K 1 . 00 V
11. 000K 1 . 00 V
1 1 . 000K 1 . 00 V
11. 000K 1 . 00 V
11 . 000K 1 . 00 V
11 . 000K 1 . 0 0 V
1 1 . 9 K 0 . 1 V
1175