Keithley 1801, Инструкция по эксплуатации, Страница: 34 / 93

Operation
3-11
3.3.3 Four-wire resistance measurements
The Model 1801 can make 4-wire resistance measure-
ments between 100p
Ω
and 200
Ω
. Assuming “bench
reset” conditions (see paragraph 3.12.1 of the Model 2001
Operator’s Manual), the basic procedure for making
4-wire resistance measurements is as follows:
1. Connect the input cable to the INPUTS terminals on
the preamplifier module, and connect the output leads
to the rear panel SENSE 4 WIRE jacks (see Figure
3-4). Also connect test leads to the rear panel HI and
LO INPUT jacks (these leads are necessary to apply
the source current to the DUT necessary for 4-wire
resistance measurements).
2. Set the INPUTS switch to the REAR position.
3. Press CONFIG
Ω
4, then select the desired four-wire
resistance operating conditions.
4. Press the
Ω
4 key to select the 4-wire ohms function.
5. Using the RANGE keys, choose a range consistent
with the expected resistance. (Available ranges are
from 2m
Ω
to 200
Ω
in decade steps.)
6. Connect the preamplifier input leads and the DMM
HI and LO INPUT leads to the resistance being mea-
sured, as shown in Figure 3-4.
7. Observe the display. If the “Overflow” message is
displayed, select a higher range. Use the lowest range
possible for the best resolution.
8. Take a reading from the display. If the reading is
noisy, it may be necessary to change the filter
response. (See paragraph 3.2.5 for details on
filtering.)
Zeroing
The specification term “when properly zeroed” means
that you must establish a baseline for subsequent
measurements on that range. All Model 1801 4-wire
resistance ranges require proper zeroing to achieve rated
accuracy. The zeroing procedure described below should
be performed at intervals and changes in ambient
temperature given in Appendix A.
To zero (rel) the Model 1801, follow the steps below:
1. Disable rel if presently enabled by pressing the REL
key. The REL annunciator should be off.
2. Select the range to be used for the measurement.
3. Disconnect all four leads from the signal source, then
short the ends of all four test leads together. Allow
sufficient time for thermal offsets and noise to
stabilize.
4. Press the REL key. The display will read zero.
5. Remove the short, and connect all four test leads to
the resistance to be measured.
Offset-compensated ohms
Offset-compensated ohms compensates for voltage
potentials such as thermal EMFs across the device under
test. For maximum accuracy, offset compensation should
be used for all Model 1801 resistance measurements.
Offset compensation can be enabled or disabled by
pressing CONFIG
Ω
4, and then selecting
OFFSETCOMP in the CONFIGURE OHMS-4W menu.
See paragraph 3.4.3 of the Model 2001 Operator’s Model
for additional information.
3.3.4 Frequency measurements
The Model 1801 can make ACV frequency measurements
between 1Hz and 1kHz. Assuming “bench reset” condi-
tions (see paragraph 3.12.1 of the Model 2001 Operator’s
Manual), the basic procedure for making ACV frequency
measurements is as follows:
1. Connect the input cable to the INPUTS terminals on
the preamplifier module, and connect the output leads
to the rear panel INPUT jacks (see Figure 3-5).
2. Set the INPUTS switch to the REAR position.
3. Press CONFIG FREQ, then choose the desired fre-
quency measurement configuration.
4. Press the FREQ key to select the frequency function.
5. Connect the input leads to the AC voltage source, as
shown in Figure 3-5.
CAUTION
Do not exceed 1V peak at 100mA
between the INPUTS HI and LO ter-
minals, or the preamplifier may be
damaged. (Inputs over 2mV will
require a one-minute recovery period.)
6. Take a frequency reading from the display.