Bandwidth; Scanning - Keithley 2750 User Manual

4-10 Range, Digits, Rate, Bandwidth, and Filter
Setting measurement speed — The RATE key is used to set measurement speed from the
front panel. Simply press RATE until the desired speed annunciator (FAST, MED, or
SLOW) turns on.
NOTE

Bandwidth

Bandwidth specifies the lowest frequency of interest for AC measurements. The RATE
setting determines the bandwidth setting:
•
•
•
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). For remote program-
ming, the integration rate can be set from 0.01 PLC to 50 or 60 PLC.
Table 4-4
remote programming, the FAST, MED, and SLOW annunciators are only lit when condi-
tions 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
For remote programming, the <clist> parameter is used to configure channels for a scan.
The Model 2750 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.
SLOW — 3Hz to 300kHz
MEDium — 30Hz to 300kHz
FAST — 300Hz to 300kHz
lists the front panel bandwidth settings for the AC measurement functions. For
Model 2750 Multimeter/Switch System User's Manual
Section 7.