User manual

Bandwidth
The rate setting for AC voltage and current measurements determines the bandwidth set-
ting:
• 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. How-
ever, only 120 samples (120ms) are needed for an accurate calculation because the analog
RMS converter 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
annunciators are turned off.
Table 3-1
Rate settings for the measurement functions
Function
Rate
Fast Medium Slow
DCV, DCI
ACV, ACI
Ω2W, Ω4W
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.
2000-900 (J - Aug 2010) BOOK.fm Page 7 Wednesday, October 12, 2011 12:29 PM