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HP4402.book : chapter2.fm 55 Wed Apr 23 15:29:05 1997
Power Meter Operation
Self Test
HP EPM-442A User’s Guide 2-55
Calibrator
The reference calibrator is turned on (indicated by the POWER REF LED)
and measured internally. A pass or fail result is returned.
Keyboard (Front Panel only)
The power meter enters a mode where you are invited to press any key.
When a key is pressed, its name appears on the screen. You can check that
the power meter is displaying the expected name when the relevant key is
pressed. This is a check that the power meter is receiving the correct
keyboard signal. Pressing the same key twice sequentially exits this mode
and returns you to a display that lists all the keys that were not entered.
If the test is exited without all the keys being pressed a list is displayed
showing all the keys which were not selected.
Display
Three tests are available for the display: the display assembly, display
RAM and bitmap display.
A read/write is performed on the display RAM. If the value which is
written is read back correctly, a pass is recorded, otherwise a fail is
recorded.
The liquid crystal display/ light emitting diode (LCD/LED) control circuits
are tested by making separate voltage measurements via the multiplexer
and digital signal processor. If the expected voltages are measured, a pass
is recorded, otherwise a fail is recorded. The three circuits which are
tested are the LCD contrast control, the LED brightness control and the
display temperature sensing diode.
Bitmap Display (Front Panel only)
A series of bitmaps are displayed on the power meter showing: two
checkboards, vertical lines, horizontal lines, oblique lines, all pixels on and
all pixels off. Pressing cycles you through these bitmaps. The
key stops the display and returns you to the previous menu.
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