Specifications
606 Appendix F
List of Responses to Measurement Failure
Behavior under Abnormal Measurement Conditions
Behavior under Abnormal Measurement Conditions
This section describes abnormal conditions that may occur during measurement and
explains the resulting LCD display and GPIB output and how to cope with them.
• Overload
This situation is detected when an internal circuit is temporally overloaded due to
connection or disconnection of a DUT during measurement. If this failure occurs
frequently during normal measurement, the instrument may be out of order.
• DC Bias Overload
This situation is detected when overcurrent suddenly runs in a bias circuit. If this
failure occurs frequently during normal measurement, the instrument may be out of
order.
• PLL Unlock
This situation is detected when E4991A has failed to synchronize an external reference
signal. If this failure occurs frequently during normal measurement, the instrument may
be out of order.
• DC Bias Current/Voltage Limitation
This situation is detected when set voltage or current cannot be applied because of
limited dc bias current or voltage. This does not always indicate an instrument failure.
Table F-1 Behavior under Abnormal Measurement Conditions
Event Screen display
Questionable Status
Hardware Event Register
Measurement value Suggested action
Overload "RF Overload" appears in
status line.
Bit 3 is set to 1. Indefinite Do not connect or
disconnect the DUT during
measurement.
DC bias Overload "DC Bias Overload" appears
in status line.
Bit 2 is set to 1. Measurement is
performed at a voltage
other than the set DC
bias voltage.
Do not connect or
disconnect the DUT during
measurement.
PLL Unlock "PLL Unlock" appears in
status line.
Bit 1 is set to 1. Indefinite If an external reference
signal out of specification is
input, input a signal in
accordance with the
specification.
DC bias
current/voltage
limitation is imposed
"Bias Lmt" appears in DC
bias status.
N/A Measurement is
performed at limited DC
bias voltage/current.
Change the maximum
current limit or maximum
voltage limit.