Autoranging; Relative; Configuring Rel - Keithley 2001 Operator's Manual

3.5.4 Autoranging

To enable autoranging, press the AUTO key. The AUTO an-
nunciator turns on when autoranging is selected. While au-
toranging is selected, the instrument automatically chooses
the best range to measure the applied signal.
Autoranging should not be used when op-
timum speed is required. Autoranging
speeds are covered in the specifications of
Appendix A.
Note that up-ranging occurs at 105% of range, while down-
ranging occurs at 10% of range.
To cancel autoranging, press AUTO or the RANGE
key. Pressing AUTO to cancel autoranging leaves the instru-
ment on the present range.
Pressing the RANGE
autoranged to the lowest range displays the following
momentary typical message and leaves the instrument in
autorange:
Range at minimum: 200 mVDC
The instrument operates similarly if the RANGE
pressed when the instrument has autoranged to the highest
range.
For the frequency function, pressing the AUTO key returns
the trigger level to 0.0V. The AUTO key has no effect for the
temperature function.
3.6

Relative

The rel (relative) operation subtracts a reference value from
actual readings. When rel is enabled by the REL key, the in-
strument uses the present reading as a relative value. Subse-
quent readings will be the difference between the actual
input value and the rel value. You can also enter and enable a
relative value from the CONFIG-REL display.
A rel value can be established for each measurement func-
tion. For example, a 10µA reference can be set for DC cur-
rent measurements, and a 100 Ω reference for 2-wire
resistance. The state and value of rel for each measurement
function are saved when changing functions.
Once a rel value is established for a measurement function,
the value is the same for all ranges. For example, if 100µA is
NOTE
key when the instrument has
set as a rel value on the 200µA range, then the rel is also
100µA on the 2mA, 20mA, 200mA, and 2A ranges. Similar-
ly, if 150V is set as a rel value on the 200V range, the rel is
also 150V on the 1000V, 20V, 2V, and 200mV ranges.
A relative value can be as large as the highest range for the
particular function. Table 3-27 lists the allowable range of rel
values for each function.
Selecting a range that cannot accommodate the rel value
does not cause an overflow condition, but it also does not in-
crease the maximum allowable input for that range. For ex-
ample, on the 2mA range, the Model 2001 still overflows for
a 2.1mA input.
Table 3-27
Allowable rel values
or
Function
DC voltage
AC voltage
DC current
AC current
2-wire resistance
4-wire resistance
Frequency
Temperature
key is
3.6.1 Configuring rel
From the CONFIG-REL display, you can view or change the
rel value for the present measurement function. To view or
change the rel value of a different function, you must first se-
lect it by pressing the appropriate function key.
Press the CONFIG key, and then the REL key to access the
following display:
RELVAL=+0.000000e+00
Use the cursor (
among the digits and set their desired values. If the value is
too large for the present measurement function, the follow-
ing typical message is displayed when you press ENTER:
MAXIMUM ALLOWED VAL:
1.100000e+03
and rel is not enabled. If the value is within the limits shown
in Table 3-27, you are returned to the normal reading display
with that value of rel already enabled.
Front Panel Operation
Rel range
-1.1e3 to +1.1e3 (±1100V)
-7.75e2 to +7.75e2 (±775V)
-1.2e1 to +1.2e1 (±12A)
-2.1e0 to +2.1e0 (±2.1A)
(0 to 1.05G Ω )
0 to +1.05e9
(0 to 210k Ω )
0 to +2.1e5
0 to +1.5e7 (0 to 15MHz)
-3.28e2 to +3.31e3 (-328 to +3310°)
and ) and RANGE keys to move
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