Keithley 2000, Руководство пользователя, Страница: 59 / 280

Response time
The filter parameters have speed and accuracy tradeoffs for the time needed to display, store,
or output a filtered reading. These affect the number of reading conversions for speed versus ac-
curacy and response to input signal changes.
Relative
The rel (relative) function can be used to null offsets or subtract a baseline reading from
present and future readings. When rel is enabled, 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 define a rel value for each function. Once a rel value is established for a measurement
function, the value is the same for all ranges. For example, if 50V is set as a rel value on the
100V range, the rel is also 50V on the 1000V, 10V, 1V, and 100mV ranges.
Thus, when you perform a zero correction for DCV,
Ω
2, and
Ω
4 measurements by enabling
REL, the displayed offset becomes the reference value. Subtracting the offset from the actual
input zeroes the display, as follows:
Actual Input – Reference = Displayed Reading
A rel value can be as large as the highest range.
Selecting a range that cannot accommodate the rel value does not cause an overflow condi-
tion, but it also does not increase the maximum allowable input for that range. For example, on
the 10V range, the Model 2000 still overflows for a 12V input.
To set a rel (relative) value, press REL key when the display shows the value you want as the
relative value. The REL annunciator turns on. Pressing REL a second time disables rel.
You can input a REL value manually using the mX+b function. Set M for 1 and B for any
value you want. Pressing REL enables that value to be the relative value. See Section 2 for more
information on the mX+b function.
Digits
The display resolution of a Model 2000 reading depends on the DIGITS setting. It has no ef-
fect on the remote reading format. The number of displayed digits does not affect accuracy or
speed. Those parameters are controlled by the RATE setting.
Perform the following steps to set digits for a measurement function:
1. Press the desired function.
2. Press the DIGITS key until the desired number of digits is displayed (3
½
to 6
½
).
NOTE Frequency and period can be displayed with four to seven digits.
Measurement Options 3-5