4-10 Range, Digits, Rate, Bandwidth, and Filter Model 2701 User’s Manual
Setting rate
FAST, MED, or SLOW — The RATE key is used to set rate (measurement speed from
the front panel). Simply press RATE until the desired speed annunciator (FAST, MED, or
SLOW) turns on.
NOTE The Model 2701 uses internal references to calculate an accurate and stable
reading. When the NPLC setting is changed, each reference must be updated to
the new NPLC setting before a reading is generated. Therefore, frequent NPLC
setting changes can result in slower measurement speed.
Bandwidth
Bandwidth specifies the lowest frequency of interest for AC measurements. The RATE
setting determines the bandwidth setting:
• SLOW — 3Hz to 300kHz
• MEDium — 30Hz to 300kHz
• FAST — 300Hz to 300kHz
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 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). For remote
programming, the integration rate can be set from 0.002 PLC to 50 or 60 PLC.
Table 4-4 lists the front panel bandwidth settings for the AC measurement functions. For
remote programming, the FAST, MED, and SLOW annunciators are only lit when
conditions in the table are met. In other cases, the annunciators are turned off.
Scanning
When a simple scan is configured, the present rate or bandwidth setting will apply to all
channels in the scan. When an advanced scan is configured, each channel can have its own
rate or bandwidth setting. Details to configure and run a scan are provided in Section 7.
For remote programming, the <clist> parameter is used to configure channels for a scan.
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