Keithley 2001 Operator's Manual page 52

Front Panel Operation
COUPLING
This parameter selects the input coupling for the ACV
function. When AC coupling is selected, a DC blocking
capacitor is placed in series with the input. This removes the
DC component from the RMS, average, or peak ACV
measurement.
When AC+DC coupling is selected, the blocking capacitor is
removed. Subsequent RMS, average, or peak ACV
measurements will reflect both the AC and DC components
of the signal.
While displaying readings, the present coupling setting is
shown on the bottom line, if not showing a multiple display.
You can set the ACV coupling as follows:
1. From the CONFIGURE ACV menu, select COUPLING
and press ENTER. The following menu is displayed:
SET AC COUPLING
AC AC+DC
2. Highlight the desired coupling and press ENTER.
Note that the coupling settings for ACV and ACI are
discrete. Thus, setting the coupling of ACV has no effect on
the coupling of ACI.
AC-TYPE
This parameter selects the measurement type for the ACV
function. The Model 2001 directly measures RMS, average,
and peak AC voltages. For a 330V peak-to-peak sine wave,
which is line voltage in the U.S., the measurements would
be:
• RMS = 117V
• Average = 105V (full wave rectified)
• Peak AC = 165V
The peak detector is also used to measure positive and
negative peak spikes riding on a DC signal and they are,
therefore, also configured from the AC-TYPE menu.
You can program the ACV type parameter as follows:
1. From the CONFIGURE ACV menu, select AC-TYPE
and press ENTER. The following menu is displayed:
SET ACV MEASUREMENT
RMS AVERAGE PEAK LOW-FREQ-RMS
POSITIVE-PEAK NEGATIVE-PEAK
3-20
2. Highlight the desired measurement type and press
ENTER.
RMS and LOW-FREQ-RMS: Selecting between normal
RMS mode and low frequency RMS mode depends on the
desired accuracy and speed. Low frequency RMS mode is
more accurate, but slower.
Both modes are specified between 20Hz and 2MHz, with
low frequency RMS specified additionally down to 1Hz.
Some guidelines for choosing between the two modes
follow:
• Below 50Hz, use low frequency RMS mode for its
greater accuracy.
• Between 50 and 100Hz, use either mode.
• Above 100Hz, use normal RMS mode for its greater
speed.
AVERAGE: When this item is selected, the signal path in
the instrument bypasses the RMS converter, so the average
ACV measurement is just the filtered output of a full wave
rectifier.
PEAK: For AC peak measurements, the instrument displays
the largest peak (positive or negative) of the input signal. The
measurement window is fixed at 100msec.
Note that you can configure the resolution of ACV peak
measurements from 4 digits (3.5d from SET ACV
RESOLUTION menu) to 8 digits (7.5d), but the accuracy is
specified at 4 digits. In addition, the accuracy
for AC peak measurements assume AC+DC coupling below
200Hz.
POSITIVE-PEAK and NEGATIVE-PEAK: Peak spike
measurements are available as an ACV primary display (top
line). They are also available as a DCV multiple display
(bottom line). The menu items POSITIVE-PEAK and
NEGATIVE-PEAK enable the measurement as a primary
display. See Figure 3-8 for a description of the primary
display.
After selecting a positive or negative peak spikes
measurement from the SET ACV MEASUREMENT menu,
you are asked to enter a value for the measurement window.
A typical message follows:
PEAK WINDOW = 0.1 s
This sets the time the signal is sampled before the display is
updated with a new reading. It can range from 0.1sec to
9.9sec.
2001-900-01 Rev. K/ August 2010
Specifications