Keithley 2000, User Manual, Page: 61 / 280

Bandwidth
The rate setting for AC voltage and current measurements determines the bandwidth setting:
• Slow — 3Hz to 300kHz.
• Medium — 30Hz to 300kHz.
• Fast — 300Hz to 300kHz.
Bandwidth is used to specify the lowest frequency of interest. When the Slow bandwidth
(3Hz to 300kHz) is chosen, the signal goes through an analog RMS converter. The output of the
RMS converter goes to a fast (1kHz) sampling A/D and the RMS value is calculated from 1200
digitized samples (1.2s).
When the Medium bandwidth (30Hz to 300kHz) is chosen, the same circuit is used. However,
only 120 samples (120ms) are needed for an accurate calculation because the analog RMS con-
verter has turned most of the signal to DC.
In the Fast bandwidth (300Hz to 300kHz), the output of the analog RMS converter (nearly
pure DC at these frequencies) is simply measured at 1 PLC (16.6ms).
Table 3-1 lists the rate settings for the various measurement functions. The FAST, MED, and
SLOW annunciators are only lit when conditions in the table are met. In other case, the annun-
ciators are turned off.
Table 3-1
Rate settings for the measurement functions
Function
Rate
Fast Medium Slow
DCV, DCI
ACV, ACI
Ω
2W,
Ω
4W
FREQ, PERIOD
dB, dBm (ACV)
dB, dBm (DCV)
Continuity
Diode test
NPLC=0.1
NPLC=1, BW=300
NPLC=0.1
APER=1s
NPLC=1, BW=300
NPLC=0.1
NPLC=0.1
N/A NPLC=1
NPLC=X, BW=30
NPLC=1
APER=1s
NPLC=X, BW=30
NPLC=1
N/A
NPLC=1 NPLC=10
NPLC=X, BW=3
NPLC=10
APER=1s
NPLC=X, BW=3
NPLC=10
N/A
N/A
Notes:
NPLC = number of power line cycles.
BW = lower limit of bandwidth (in Hz).
APER = aperture in seconds.
N/A = not available.
X = setting ignored.
Measurement Options 3-7