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Section 5: Basic Digital Multimeter (DMM) Operation
Series 3700 System Switch/Multimeter User's Manual
5-26
3700S-900-01 Rev. C / July 2008
CAUTION
Do not use a fuse with a higher current rating than specified or
instrument damage may occur. If the instrument repeatedly
blows fuses, locate and correct the cause of the trouble before
replacing the fuse.
NOTE
Model 3721 card supports both AC and DC current measurements.
Refer to the
Schematic
(on page 5-11) contained in the User's
manual. The Model 3721 card has replaceable fuses. For replacement
information, refer to
Model 3721: AMPS channels fuse replacement
(on page 9-24).
1. Turn off the power and disconnect the power line and connections.
2. From the rear panel, gently push in the AMPS fuse holder with a flat blade
screwdriver and rotate the fuse holder one-quarter turn counterclockwise.
3. Remove the fuse and replace it with the same type (3A, 250V, fast-blow, 5 ×
20mm). The Keithley Instruments part number is FU-99-1.
4. Install the new fuse by reversing the procedure above.
Resistance measurements
The Series 3700 uses the constant-current method to measure resistance
ranges from 1 to 1M . The Series 3700 sources a constant current (I) to the
resistance and measures the voltage (V). Resistance (R) is then calculated (and
displayed) using the known current and measured voltage (R = V/I). For the
10M and 100M ranges, the ratiometric method is used to measure
resistance.
Basic resistance measurements
The Series 3700 can make resistance measurements from 0.1µ to 120M .
For resistances >1k , the 2-wire ( 2) method is typically used for
measurements. For resistances 1k , the 4-wire ( 4) measurement method
should be used to cancel the effect of test lead (and channel path) resistances.