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

Front Panel Operation
Note that the frequency and temperature functions have just
one range. For the frequency functions, the RANGE  and
 keys increase and decrease the trigger level by 0.5%. On
temperature the keys have no effect.
3.5.4

Autoranging

To enable autoranging, press the AUTO key. The AUTO
annunciator turns on when autoranging is selected. While
autoranging 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.
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  or 
key. Pressing AUTO to cancel autoranging leaves the
instrument on the present range.
Pressing the RANGE  key when the instrument has
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  key is
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
instrument uses the present reading as a relative value.
Subsequent 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
function. For example, a 10µA reference can be set for DC
current measurements, and a 100 reference for 2-wire
3-52
NOTE
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
set as a rel value on the 200µA range, then the rel is also
100µA on the 2mA, 20mA, 200mA, and 2A ranges.
Similarly, 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
values for each function.
Selecting a range that cannot accommodate the rel value
does not cause an overflow condition, but it also does not
increase the maximum allowable input for that range. For
example, on the 2mA range, the Model 2001 still overflows
for a 2.1mA input.
q~ÄäÉ=PJOT
Allowable rel values
Function Rel range
DC voltage -1.1e3 to +1.1e3
AC voltage -7.75e2 to +7.75e2
DC current -1.2e1 to +1.2e1
AC current -2.1e0 to +2.1e0
2-wire resistance 0 to +1.05e9
4-wire resistance 0 to +2.1e5
Frequency 0 to +1.5e7
Temperature -3.28e2 to +3.31e3
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
select 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 ( and
among the digits and set their desired values. If the value is
too large for the present measurement function, the
following typical message is displayed when you press
ENTER:
MAXIMUM ALLOWED VAL:
1.100000e+03
2001-900-01 Rev. K/ August 2010
lists the allowable range of rel
(±1100V)
(±775V)
(±12A)
(±2.1A)
(0 to 1.05G)
(0 to 210k)
(0 to 15MHz)
(-328 to +3310°)
) and RANGE keys to move