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Front Panel Operation - 5
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2 - Querying and Clearing Output Protection
The dc source will disable its output if it detects an overvoltage or overcurrent fault condition.
Other automatic fault conditions (such as overtemperature) also will disable the output.
Query and clear the dc source overcurrent protection feature as follows:
Action Display
1. On the Function keypad, press Protect. In this example, OC indicates that
an overcurrent condition has occurred. Other protection indicators are: OT
(overtemperature), OV (overvoltage), RI (remote inhibit), and FS (internal
fuse is open).
OC -- -- -- --
2. On the Function keypad, press Current. This displays the present output
current limit. (10% of the maximum rating is the default current limit
setting).
CURR 0.2045
(2 amp unit)
3. To restore normal operation after the cause of the overcurrent condition has
been removed, press Shift, Prot Clr. The OCP annunciator then will go
off.
3 - Making Front Panel Measurements
When the dc source is operating in front panel meter mode, all front panel measurements are
calculated from a total of 2048 readings taken at a 46.8 microsecond sampling rate. The unit
alternates between voltage and current measurements. Therefore, the data acquisition time for a
single front panel voltage or current measurement is about 100 milliseconds. The sample rate and
number of data points are fixed, and there are no trigger controls for front panel measurements.
This fixed sampling rate and data acquisition time combined with a built-in windowing function,
reduces errors due to sampling a non-integral number of cycles of a waveform for frequencies of
25 Hz or greater. Note that the windowing function is less accurate when measuring output
waveforms for frequencies less than 25 Hz, causing the front panel meter to jitter.
When controlling the unit over the HP-IB interface, you can vary both the sampling rate and the
number of data points in each measurement. If you are using the HP 66332A dc source to measure
waveform data, the HP-IB interface also lets you qualify the triggers that initiate the
measurements. With this flexibility, measurement accuracy can be improved for waveforms with
frequencies as low as several Hertz. Refer to chapter 3 in the Programming Guide for more
information.
Two current measurement ranges can be selected in the Input menu. A high current range is
available for measuring output currents up to the 30% higher than the maximum rating of the dc
source. A low current range is available for improved resolution when measuring output currents
below 20 milliamperes. The low current measurement range is accurate to 0.1% of the reading
±2.5 microamperes. When the current Range is set to AUTO, the unit automatically selects the
range that provides the best measurement resolution.
NOTE: If the front panel display indicates OVLD, the output has exceeded the
measurement capability of the instrument. If the front panel display indicates
-- -- -- -- -- -- , an HP-IB measurement is in progress.