READ[<chan>]

The READ? command is used to cause a measurement and to retrieve the readings from that measurement. It is equivalent to executing the commands: ABORt, INITiate:IMMediate, FETCh<chan >?.

Subsystem

READ[<chan >]?

[query only]

Syntax

 

 

READ?

READ[<chan >]? returns readings from the specified channel in the format specified by the FORMat:DATA command.

Parameters

Parameter

Parameter

Range of

Default

Name

Type

Values

Units

 

 

 

 

chan

numeric

1 2

none

 

 

 

 

Comments READ? or READ1? will return data from channel 1 only. READ2? will return data from channel 2 only.

A READ1? followed by a READ2? will take two sets of measurements since an INITiate is done with each read. If it is desired to look at each channel separately for readings taken during the same time period, use the INITiate and FETCh? sequence of commands instead of READ?.

There are a few settings which, if allowed, would cause READ? to deadlock and never complete. TRIGger:COUNt INFinite and ARM:COUNt INFinite are not allowed because the measurement is continuous and therefore would never finish. Also, ARM:SOURce BUS or HOLD and TRIG:SOURce BUS or HOLD are not allowed because the parser would be unable to accept any commands to arm or trigger the instrument during measurement because the READ? command would not have completed. Any of the above settings active during a READ? command will cause an error to occur and no measurements to be taken.

The number of readings that READ? is going to return for each channel can be calculated as

(number of start triggers) * (pre-arm readings + post-arm readings)

The above equation may be built from the following queries:

(ARM:COUNt?) * (TRIG:COUNt?)

READ[<chan>] Subsystem

Command Reference 249

Page 249
Image 249
HP E1429A manual READchan Subsystem Command Reference