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HP4402.book : chapter2.fm 78 Fri Feb 12 15:32:45 1999
Power Meter Operation
Self Test
2-78 HP E4419B User’s Guide
• UART Configuration - confirms that the baud rate, stop bits and
parity settings are correctly configured on the UART.
• Local Loop Back - Tx and Rx on the UART are internally
connected and a test message is sent to confirm correct operation.
• RS232/RS422 Loop Back - A message is sent via the UART and
transceivers using an external loop back connector (refer to the
E4418B/E4419B Service Guide).
Option 001 Battery
This test checks that the capacity of the option 001 battery has not
decayed below 70 % of its original value. The test is only performed on
power meters fitted with option 001.
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.