User`s guide

Chapter 4 Features and Functions

Scanning

• While a scan is running, you can perform some low-level control

operations on modules that do not contain channels in the scan list.

For example, you can open or close channels or issue a Card Reset on

switching modules that do not contain channels in the scan list.

However, you cannot change any parameters that affect the scan

(channel configuration, scan interval, scaling values, alarm limits,

Card Reset, etc.) while a scan is running.

• When you add a digital read (multifunction module) to a scan list,

that port is dedicated to the scan. The instrument issues a Card Reset

to make that port an input port (the other port is not affected).

• While a scan is running, you can perform low-level control operations

on any channels on the multifunction module that are not in the scan.

For example, you can output a DAC voltage or write to a digital port

(even if the totalizer is part of the scan list). However, you cannot

change any parameters that affect the scan (channel configuration,

scan interval, Card Reset, etc.) while a scan is running.

• If a scan includes a read of the totalizer, multifunction module, the

count is reset each time it is read during the scan only when the

totalizer reset mode is enabled (TOTalize:TYPE RRESet command

or the Advanced menu for the totalizer).

• If you install a module while a scan is running, the instrument will

cycle power and resume scanning. If you remove a module while a

scan is running, the instrument will cycle power, and it will not

resume scanning when the reboot completes. If you are logging to a

USB drive, the instrument will not log any scans that occur between

the removal of the module and the reboot of the instrument.

• You can use either the internal DMM or an external DMM to make

measurements of your configured channels. However, the instrument

allows only one scan list at a time; you cannot scan some channels

using the internal DMM and others using an external DMM.

Readings are stored in 34970A/34972A memory only when the

internal DMM is used.

• If the internal DMM is installed and enabled, the instrument will

automatically use it for scanning. For externally-controlled scans, you

must either remove the internal DMM from the 34970A/34972A or

disable it (see “Internal DMM Disable” on page 145).

34970A Refresh UG.book Page 92 Wednesday, February 17, 2010 12:34 PM