Keithley 610C, Instruction Manual

Page: 13 / 44

2-3. VOLTAGE MEASUREMENTS.
B.
Normal Measurements. When the RANGE
switch is set to VOLTS position the 610e can be used
to measure voltages from .001 volt full scale to 100
volts. In this mode the input impedance is greater
than 1014 ohms shunted by 20 picofarads. The input
impedance can be reduced when necessary by setting the
RANGE switch to AMPERES as discussed in paragraph 2-3c.
1. Set the controls as follows:
ZERO CHECK Switch
RANGE Switch
Multiplier Switch
FEEDBACK Switch
METER Swi t ch
LOCK
VOLTS
100
NORMAL
CENTER ZERO
2.
Connect the input source to the
UHF
input.
Unlock the ZERO CHECK switch to make a reading.
Increase the meter sensitivity using the Multiplier
switch to obtain a useable on-scale reading.
The
METER switch should be set to either
+
or - to
obtain the rated voltage accuracy.
b. Guarded Measurements. This method is
useable when a Keithley Model 6108 input cable is
available.
The Model 6108 is a specialized triaxial
cable with a mating
UHF
connector. The cable is
terminated with three color-coded alligator clip leads.
The leads are identified as shown in Table 4.
TABLE 4.
Model 6108 Input Cable.
Lead Color
Terminal Function
Red
Input High
Black
Inner Shield (Guard)
Green
Outer Shield (Ground)
1. Set the controls as follows:
ZERO CHECK Switch
RANGE $wi tch
Multiplier Switch
FEEDBACK Switch
METER Swi tch
LOCK
VOLTS
100
NORMAL
CENTER ZERO
2. Connect the Model 6108 to the UHF input.
Connect the black banana plug to the Xl OUTPUT
on the rear panel of the instrument. Connect the
remaining alligator clip leads as shown in Figure
5.
c. Decreased Resistance. The input resistance
can be reduced for applications where very high input
resistance is not required. Set the RANGE switch to
one of the AMPERES ranges where the input is shunted
by a resistor. The input resistance is then the re­
ciprocal value of the AMPERES setting. For instance,
to obtain an input resistance of 10 megohms (107n)
set the RANGE switch to the 10-7 AMPERES range. Then
adjust the Multiplier switch to the full scale volt­
age desired. The 6l0C can now be used for voltage
measurements as discussed in paragraphs 2-3a and b.
d. High Voltage Measurements. Measurements can
be made up to
30
kilovolts using one of the Voltage
Divider probes listed in Table 5. The full scale
voltage range is determined by multiplying the divider
ratio times the Multiplier s"etting.
TABLE S
Voltage Divider Probes
Model Divider Ratio Accuracy
6102A
6103A
+
5% at 10 kv
2-4. CURRENT MEASUREMENTS.
a. Normal Current Measurements. When the FEEDBACK
switch is set to NORMAL the current is determined .by
measuring the voltage drop across a RANGE resistor
shunting the 6l0C input. This method is useable for
any current range where low noise is essential.
1. Set the front panel controls as .follows:
ZERO CHECK Switch
RANGE Swi tch
Multiplier Switch
FEEDBACK Switch
METER Swi t ch
LOCK
10-1 AMPERES
1
NORMAL
CENTER ZERO
2. Connect the 610C input terminals in series with
the current to be measured. Unlock the ZERO CHECK
switch to make a reading. Increase the sensitivity
using the RANGE switch. The full scale current is
determined by multiplying the RANGE setting times
the Multiplier setting. Use the smallest Multiplier
setting to obtain the best accuracy: The input voltage
drop of the 610C in the NORMAL mode is a function of
the Multiplier setting and therefore the loading
error should be noted as shown in Figure 6.
TABLE 6.
Response Speed For Fast Current Measurements.
Range Rise Time Noise (Peak-to-Peak)
� No C
10-l4to 2.0 2.0 2.0
6
x
10-15 loS
x
10-14 7
x
10-13
10-11
10-10
.45
.4S
.4S 8.5
x
10-14 2
x
10-13 2.5
x
10-12
10-9 .07 .07 .07 6.8
x
10-13 3.2
x
10-12 2
x
10-11
10-8
.01S
.01S .01S
6
x
10-12
2.S
x
10-11
2
x
10-10
10-7 .003 .003 .003 4
x
10-11 8
x
10-11 3
x
10-10
10-6
.003 .003 .003 loS
x
10-10
3.3
x
10-10 8.S
x
10-10
5