
Power-On Self Test (POST)
When an N-20P is switched on, a sequence of diagnostic tests are run that examine the instruments electronics
and display functions. This power-up self-test consists of the following events:
Immediately after power is switched on, the instrument simultaneously:
•
Displays the number "8" in all six Oxygen Saturation and Pulse Rate display field segments;
•
Illuminates all 14 pulse rate amplitude indicator segments; and
•
Illuminates the Pulse Search and Low Battery indicators.
During the next few seconds, the instrument:
•
Switches off the display backlight;
•
Displays three digits in the Oxygen Saturation display field representing the software version (for example,
123 is software version 1.2.3).
•
Displays the printer status in the display fields; that is, either "Pr On" or "Pr OFF".
If a sensor is attached to the instrument, a zero ("0") appears in first position of the display fields, and the Pulse
Search indicator flashes; if no sensor is attached to the instrument, horizontal dashes appear in all six Oxygen
Saturation and Pulse Rate display fields, and the Pulse Search indicator flashes.
After approximately 1 minute:
•
A short beep occurs and the instrument automatically switches off.
If at any time during the test sequence "Err" followed by a code number is displayed, make note of the error
code and refer to error code descriptions in this manual.
Low Battery Test
The N-20P CPU monitors the battery voltage level and alerts the user via the Low Battery indicator when
voltage is getting low. To test the proper function of the Low Battery indicator, connect the N-20P to an
external, variable DC power supply.
Battery voltage levels below are accurate; however, slight variations may exist due to differences between
batteries of different manufacturers. To that point, the N-20P operates normally at voltages above 4.0 VDC.
When the battery voltage drops below 4.5-3.8 VDC, the Low Battery indicator is lit, and the two lowest
segments of the battery level meter are lit when the battery check button is pressed. When the voltage level
drops below 4 VDC, the N-20P continues to display Oxygen Saturation and Pulse Rate values, but the printer no
longer operates; otherwise, the N-20P operates normally.
Battery voltage levels below 4.0-3.4 VDC cause the Low Battery indicator to begin flashing. When the battery
check button is pressed only the lowest segment of the Low Battery indicator will illuminate.
When the battery voltage level drops below 4.0-3.4 VDC, the N-20P turns itself off.
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