50
2553/ 2553E Command Guide
Formatting Measurement Results
Data read from any bank always has a <SP> character (decimal 20) as the first character,
and <NL> (with the IEEE488.1 interface EOI line asserted) as the last character.
If more than one measurement result is included in the data transmitted from the 2553/
2553E bank, then the comma character separates them.
In this manner the user can easily synchronize "
parsing
" and terminating the set of
measurement results using any of the standard methods. Using an exact character count
to terminate reading the measurement results is strongly discouraged as this can lead to
serious synchronization problems, particularly in the presence of noise signals. The user
is recommended to use either the <NL> character (i.e., the EOS method) or the EOI line
of the IEEE488.1 interface as the terminator for the set of measurement results.
Similarly, the user is discouraged from using character count within the string to identify
the position of individual measurement results, but is recommended to parse the receive
data string using the comma characters to delimit between individual measurement
results. In this manner the parsing function is immune to noise interference.
Additionally, any future changes in the exact syntax of the data returned from the 2553/
2553E shall be accommodated automatically, without the user being forced to rewrite
software for the controller.
It should also be noted that this method of formatting the data from the 2553/ 2553E is
identical in nature (but not in detail) to all other
Vitrek
products, and
following the
recommended method will accommodate all products.
Once the user has started to read the contents of a buffer, i.e., after the initial <SP>
character has been fully transmitted from the 2553/ 2553E, updates of that bank are
blocked until the entire contents have been transmitted from the 2553/ 2553E. If the user
only reads a portion of a buffer, then this bank becomes "
frozen
" until the remainder is
subsequently read by the controller. If it is desired to abort reading measurement results
from a buffer during a transfer, then the IFC IEEE488.1 Interface command should be
used to clear this. The banks do not require reprogramming after the IFC command.
Some interface controller software use the name CLI rather than IFC.
Each measurement result read from a bank takes one of the following formats, dependant
on the type of data for the specified measurement result.
Several result definitions yield multiple formatted results, in this case it is possible that
the 6000 character limit on the total formatted data may be reached before the limit of 50
definitions is reached. During decode this is detected and a command error is raised if
this occurs.
Floating-Point Measurement Results
Most measurement results are "
floating
point
" and are formatted as an ASCII string
floating-point value, which always uses seven ASCII characters. The value is always
expressed in decimals, which may or may not contain a decimal point. Leading zero
suppression is used, with the polarity indicating character (either the <SP> or minus
Summary of Contents for Xitron 2553
Page 1: ...IEEE488 COMMAND GUIDE 2553 2553E Three Phase Power Analyser ...
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