Keithley 2002, User Manual, Page: 29 / 366

Front Panel Operation
2-12
SPEED
The SPEED parameter sets the integration time of the A/D
converter, the period of time the input signal is measured
(also known as aperture). The integration time affects the
usable resolution, the amount of reading noise, as well as the
ultimate reading rate of the instrument. From the front panel,
the integration time is specified in parameters based on a
number of power line cycles (NPLC), where 1 PLC for 60Hz
is 16.67msec and 1 PLC for 50Hz and 400Hz is 20msec.
The SPEED parameters for all functions (except frequency)
are explained as follows:
FAST:
Sets integration time to 0.01 PLC. Use FAST if speed
is of primary importance at the expense of increased reading
noise and less usable resolution.
MEDIUM:
Sets integration time to 0.1PLC. Use MEDIUM
when a compromise between noise performance and speed is
acceptable.
NORMAL:
Sets integration time to 1 PLC. A compromise
like MEDIUM, but NORMAL provides better noise perfor-
mance at the expense of speed.
HIACCURACY:
Sets integration time to 10 PLC. Use
HI-ACCURACY when high common-mode and normal-
mode rejection is required.
SET-SPEED-EXACTLY:
When this parameter is selected,
the current PLC value is displayed. By using the cursor keys
(
and ) and the RANGE
▲
and
▼
keys, you can enter
any PLC value from 0.01 to 50. Be sure to press ENTER
after keying in a new value. Note that an integer PLC value
will increase noise rejection.
SET-BY-RSLN:
This parameter optimizes the integration
time for the present resolution setting. See Table 2-8 for the
default integration times of the DCV and ACV functions.
The default set-by-resolution integration times of other func-
tions are listed in Tables 2-13, 2-18 and 2-24.
FILTER
FILTER lets you set the digital filter response. The filter
menu is available from the function configuration menus (i.e.
CONFIGURE DCV) or by pressing CONFIGURE FILTER
with the desired function already selected. All of the param-
eters (menu items) for FILTER are explained in paragraph
2.9. Since the AUTO parameter has specific effects on DCV
and ACV, it is covered here.
AUTO:
This parameter for a digital filter optimizes its use
for the present measurement function. The defaults for auto-
matic filtering of DCV and ACV are listed in Table 2-9.
Table 2-8
DCV and ACV integration times set-by-resolution
Measurement
function and type
Resolution
Integration
time
DCV 3.5d, 4.5d
5.5d
6.5d
7.5d
8.5d 0.01 PLC
0.02 PLC
0.10 PLC
1.00 PLC
10.00 PLC
DCV peak spikes 3.5d (to 7.5d) Not used
RMS, average 3.5d, 4.5d
5.5d
6.5d, 7.5d, 8.5d 0.01 PLC
0.02 PLC
10.00 PLC
Low frequency RMS 3.5d to 8.5d Not used
ACV peak 4d (to 8d) Not used
Notes:
1. For DCV measurements, if the integration time is SET-BY-RSLN
and the resolution AUTO, the integration time will be 1.0 PLC and
the resolution 7.5 digits.
2. For RMS and average measurements, if the integration time is SET-
BY-RSLN and the resolution is AUTO, the integration will be 1.0
PLC and the resolution 5.5 digits.
3. For DCV peak spikes, low frequency RMS, and ACV peak measure-
ments, the integration time setting is ignored.
4. The resolution of DCV peak spikes can be from 3.5d to 8.5d, but the
accuracy is specified at 3.5d. The resolution of ACV peak can be
from 4d to 8d, but the accuracy is specified at 4d.