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

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Image 225
HP E1429A manual FETChchan Subsystem Command Reference