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• The data may be read any number of times, as long as no parameters have
changed which could affect new data (such as changing TRIGger:STARt:COUNt,
ARM:STARt:COUNt, SENSe:SWEep:OFFSet:POINts, *RST, *RCL, etc.). If
any measurement parameters are changed, then error -230;"Data corrupt or stale"
will occur.
• The number of readings that FETCh? is going to return for each channel can be
determined two ways. The simplest way is to use the FETCh:COUNt? query. This
will return how many readings will be fetched. The second way is to calculate
how many readings should have been taken. This number is calculated as:
(number of start triggers) * (pre-arm readings + post-arm readings)
The above equation may be built from the following queries:
(ARM:STARt:COUNt?) * (TRIG:STARt:COUNt?)
The number of pre-arm readings may be determined by taking the absolute value
of the query SENSe:SWEep:OFFSet:POINts? which returns either 0 (no pre-arm
readings), or a negative number which is the pre-arm count.
If the measurement was ABORted, then FETCh:COUNt? is the only reliable way
to determine how many readings will be returned by the FETCh<chan >?
• As noted immediately above, it is possible to calculate the end of pre-arm data
and the beginning of post-arm data when both are present in a measurement. The
data will always be returned with the specified number of pre-arm readings
followed by post-arm readings.
• If the measurement was aborted and pre-arm readings were specified, there is no
way to determine how many readings (if any) are post-arm. The HP E1429 will
attempt to bring back TRIGger:STARt:COUNt number of readings and if there
are not that many, it will bring back as many readings as were taken.
• Related Commands: ABORt, FORMat:DATA, INITiate:IMMediate, READ?,
ARM:STARt:COUNt, TRIGger:STARt:COUNt,
SENSe:SWEep:OFFSet:POINts, STATus subsystem
• *RST Condition: none
Example 1 Obtaining readings from the HP E1429
CONF1:ARR:VOLT (30),.6,(@1) Configure for 30 readings on channel 1,
port 1
INIT Take the measurement
FETC? Get readings from channel 1.
FETCh[
<chan>
] Subsystem Command Reference 225