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Chapter 2 Hardware Overview
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National Instruments Corporation 2-13 NI 5911 User Manual
Multiple Record
After the trigger has been received and the posttrigger samples have been
stored, the NI 5911 can be configured to begin another acquisition that is
stored in another memory record on the board. This is a multiple record
acquisition. To perform multiple record acquisitions, the NI 5911 is
configured to the number of records to be acquired before starting the
acquisition. The NI 5911 acquires an additional record each time a trigger
is accepted until all the requested records have been stored in memory.
This process does not require software intervention after the initial setup
has been completed.
Between each record, there is a dead time of approximately 5 µs during
which the trigger is not accepted. During this time, the memory controller
is setting up for the next record. There may also be additional dead time
while the minimum number of pretrigger samples are being acquired.
Figure 2-9 shows a timing diagram of a multiple record acquisition.
Figure 2-9.
Multiple Buffer Acquisition
Errors During Acquisition
The NI 5911 has circuitry to detect error conditions that may affect the
acquired data. The NI 5911 uses a heater circuit to maintain constant
temperature on the critical circuitry used in flexible resolution mode. If
this circuit is unable to maintain the temperature within specification, an
error is generated. This error indicates that the temperature of the ADC is
out of range and should be recalibrated by performing an internal
calibration. During acquisition in flexible resolution mode, an error will be
generated if the input to the ADC goes out of range for the converter. The
Trigger
Acquisition
In Progress
Buffer
= Trigger Not Accepted (Pretrigger Points Not Acquired)
= Trigger Not Accepted (5 µs Dead Time)
= Trigger Not Accepted (Acquisition in Progress)
= Trigger Accepted
12
1
123
2
3
5 µS
CBIHWum.book Page 13 Thursday, October 29, 1998 1:56 PM