Keithley 2790, Reference Manual

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4-10 Model 2790 SourceMeter
®
Switch System Reference Manual
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. 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 lists the front panel bandwidth settings for the AC measurement functions. For
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 (7702 only)
When a simple scan using the 7702 module 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.
Remote programming — rate and bandwidth
Rate and bandwidth commands
The commands to set the integration rate and bandwidth are listed in Table 4-5 . Additional
information on these commands follows the table.
klqb
Query commands are not included in Table 4-5 . All commands for the SENSe
subsystem are provided in Table 15-5 .