User`s guide

53220A/53230A User’s Guide 69
53220A/53230A Measurements 3
The presence of a valid external reference can be determined programmati-
cally with the command:
[SENSe:]ROSCillator:EXTernal:CHECk ONCE
Prior to sending the command, SENSe:ROSCillator:SOURce EXTernal
and SENSe:ROSCillator:SOURce:AUTO OFF must be set.
The following example checks for an external reference signal applied to the
Ext Ref In connector.
SENS:ROSC:SOUR EXT // set source, also disables
// automatic source selection
SENS:ROSC:EXT:CHEC ONCE // check for valid signal
SYST:ERR? // read the error queue
The error queue can be read from the front panel as follows:
The status of the external reference (time base) is also monitored by the
counter’s Questionable Data register. The register can be queried with the
command: