Omega Engineering OMB-NETSCAN, Руководство пользователя

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Registers, Data Formats, & Queries Appendix D
D-18 NetScan User’s Manual
Buffer Overrun With One Trigger Block
When only one trigger block is in the buffer, a buffer overrun will erase the entire pre-trigger. If the controller
was reading pre-trigger data from the buffer, the next scan read will be the trigger point.
If no pre-trigger was configured or the pre-trigger has already been read, a buffer overrun will only erase the
oldest scan in the buffer. If the scan being erased is currently being read, the contents of the read scan will be in
error. If an overrun condition is detected by the controller during a read operation, any further reading must be
considered corrupt until a buffer reset is issued. This can be done by either resetting the buffer with a *B
command and/or reading the remaining data out of the buffer until it is clear.
Buffer Overrun With Multiple Trigger Blocks
When more than one trigger block is in the buffer, a buffer overrun will erase the oldest trigger block. If the
block being erased is currently being read, the block read will be terminated and the read pointer will be
advanced to the start of the next block. If an overrun condition is detected by the controller during a read
operation, any further reading must be considered corrupt until a buffer reset is issued. This can be done by
either resetting the buffer with a *B command and/or reading the remaining data out of the buffer until it is clear.
Real Time Clock
NetScan contains a programmable battery-backed real-time clock which has a resolution of 1mS. The clock is
set at the factory in Eastern Standard time (U.S.). The time and date are used to tag the trigger point in each
trigger block and HLL register. This data is incorporated into the Acquisition Buffer.
Open Thermocouple/Range Error Checking
The NetScan has built-in facilities for detecting open thermocouple and range errors, one in hardware and two in
software:
•
In hardware, the thermocouple cards contain circuitry to detect open thermocouples.
•
In software, software detection routines exist to sense if the input a/d maximizes and to detect if an
input exceeds the linearization limits.
If an open thermocouple/range error is detected, the Error Status Register will be set denoting that this particular
error condition exists. The offending channel(s) can be determined by reading their values. If a channel is in
error, its value will be:
±3276.70
if temperature channel (assuming units of °C)
±005.7670000
if Volts channel
Note: Open thermocouple/range error checking is only performed on channels previously activated by
the
C
Command.