Bristol 428 - Page 47

Model 428 User’s Manual REMOTE COMMUNICATIONS
Bristol Instruments, Inc. 47
*STB?
Description
The *STB (status byte) query returns the current value of the
instrument's status byte.
Query Response
Returns an integer that is the sum of all the bit values for those bits that
are set. See the instrument Status Byte table.
Instrument Status Byte
BIT
BIT VALUE
CONDITION
5
32
A bit is set in the questionable register (see STATus subsystem)
3
8
The errors in the error queue (see SYSTem subsystem)
2
4
A bit is set in the event status register
Measurement Instructions
The measurement instructions are used to return a reading to the computer. The three
basic measurement instructions are MEASure, READ, and FETCh. Functions for these
instructions are POWer, ENVironment, FREQuency, WAVelength, and WNUMber.
The :FETCh command will return a reading based on the last complete scan of the
instrument’s interferometer. Using :FETCh, it is possible to collect new measurements at
the instrument's specified measurement rate. However, if :FETCh queries are made
faster than the instrument's measurement rate, it is possible to get the same reading
twice. Old readings are indicated by a bit in the questionable status register.
The :MEASure command will return a reading based on the next scan cycle of the
instrument’s interferometer. The :READ command will return a reading based on the
current scan of the instrument’s interferometer. The :MEASure and :READ commands
guarantee that each reading returned is a new one. However, because :MEASure waits
until after the end of the current measurement cycle before returning a reading,
measurement rates can be as slow as half the instrument's scan rate. To get multiple
measurement types from a single scan (i.e., WAVelength, POWer, etc.), use :READ
followed by one or more :FETCh queries.
The :MEASure command can be considered a macro that executes multiple SCPI
commands and is equivalent to:
:ABORt
:INITiate
:FETCh[ : <function> ]?
{ :MEASure | :READ | :FETCh } { :ARRay | :SCALar} { :POWer | :ENVironment | :FREQuency |
:WAVelength | :WNUMber }?
Description
Queries a reading of the given type from the measurement subsystem.
Query Response
See below.
Examples
See below.