Features and Functions 4
Keysight 34970A/34972A User’s Guide 151
Alarm Limits
The instrument has four alarms which you can configure to alert you when a
reading exceeds specified limits on a channel during a scan. You can assign a high
limit, a low limit, or both to any configured channel in the scan list. You can assign
multiple channels to any of the four available alarms (numbered 1 through 4). For
example, you can configure the instrument to generate an alarm on the Alarm 1
output when a limit is exceeded on any of channels 103, 205, or 320.
You can also assign alarms to channels on the multifunction module. For example,
you can generate an alarm when a specific bit pattern or bit pattern change is
detected on a digital input channel or when a specific count is reached on a
totalizer channel. With the multifunction module, the channels do not have to be
part of the scan list to generate an alarm. For complete details, see “Using Alarms
With the Multifunction Module” on page 159.
Alarm data can be stored in one of two locations depending on whether a scan is
running when the alarm occurs.
1 If an alarm event occurs on a channel as it is being scanned, that channel’s
alarm status is stored in reading memory as the readings are taken. Each
reading outside the specified alarm limits is logged in memory. You can store
up to 50,000 readings in memory during a scan. You can read the contents of
reading memory at any time, even during a scan. Reading memory is not
cleared when you read it.
2 As alarm events are generated, they are also logged in an alarm queue,
separate from reading memory. This is the only place where non-scanned
alarms get logged (alarms during a monitor, alarms generated by the
multifunction module, etc.). Up to 20 alarms can be logged in the alarm
queue. If more than 20 alarm events are generated, only the first 20 alarms are
saved). Even if the alarm queue is full, the alarm status is still stored in reading
memory during a scan. The alarm queue is cleared by the *CLS (clear status)
command, when power is cycled, and by reading all of the entries. A Factory
Reset (*RST command) does not clear the alarm queue.
– You can assign an alarm to any configured channel and multiple channels can
be assigned to the same alarm number. However, you cannot assign alarms on
a specific channel to more than one alarm number.
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