Agilent 34980A Multifunction Switch/Measure Unit *34980-90005*
Agilent 34980A Multifunction Switch/Measure Unit *34980-90005*
Agilent 34980A Multifunction Switch/Measure Unit *34980-90005*
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Features and Functions 3<br />
The Analog Bus relays are automatically opened and closed as required<br />
during the scan to connect to the internal DMM for the measurement.<br />
For example, all 2- wire measurements use the ABus1 (MEAS) relays; for<br />
4-wire measurements, the ABus2 (SENS) relays are used in addition to<br />
the ABus1 relays.<br />
When the scan is initiated, the instrument will open all channels in<br />
banks that contain one or more channels in the scan list.<br />
In order to guarantee that no signals are connected to the Analog Buses<br />
prior to the scan, the instrument will open all ABus1 relays (applies to<br />
all banks in all slots). In banks that contain channels in the scan list,<br />
the instrument will also open all ABus2 relays (regardless of whether<br />
4- wire measurements are involved). If no channels configured for<br />
4- wire measurements are included in the scan list, the state of the<br />
ABus2 relays in the non- scanned banks is not altered.<br />
The state of the ABus3 and ABus4 relays is not altered and these relays<br />
remain available for use during the scan. However, be sure to use<br />
CAUTION when closing these relays on banks involved in the scan.<br />
While the scan is running, any signals present on ABus3 and/or ABus4<br />
will be joined with the scanned measurement on ABus1 and ABus2.<br />
While the scan is running, the instrument prevents use of all channels<br />
in banks that contain one or more channels in the specified scan list<br />
(these channels are dedicated to the scan). In addition, the instrument<br />
prevents use of all ABus1 and ABus2 relays on banks containing<br />
channels in the scan list. If one or more channels configured for 4- wire<br />
measurements are included in the scan list, then the rules for ABus2<br />
relay operations are extended to the non- scanned banks as well.<br />
If the ABus1 relay used for current measurements (channel 931 on<br />
34921A only) is not closed prior to the initiation of the scan, the four<br />
current channels (channels 41 through 44) are not affected by the scan.<br />
However, if the ABus1 relay is closed, the instrument will open the<br />
ABus1 relay as well as the four associated current channels in a<br />
make- before- break fashion.<br />
When you add a digital read (digital modules) to a scan list, the<br />
corresponding channel is dedicated to the scan. The instrument issues a<br />
Card Reset to make that channel an input channel (the other channel is<br />
not affected).<br />
While the scan is running, you can perform low- level control operations<br />
on any channels on the digital modules that are not in the scan. <br />
For example, you can output a DAC voltage or write to a digital channel<br />
(even if the totalizer is part of the scan list). However, you cannot<br />
change any parameters that affect the scan (channel configuration, <br />
scan interval, Card Reset, etc.) while a scan is running.<br />
If a scan includes a read of the totalizer, the count is reset each time it<br />
is read during the scan only when the totalizer reset mode is enabled.<br />
<strong>Agilent</strong> <strong>34980A</strong> Mainframe User’s Guide 109