Teledyne MX300 - Manual (Page 35)

Portable Oxygen Monitor Service Instructions
Teledyne Analytical Instruments 27
Symptom Why What To Do
C) Calibrate.
Note: In the event that none of these procedures produces desired results, remove the
batteries and return the unit to Teledyne for repair.
3.9 Watchdog
The MX300 is equipped with a watchdog circuit that continuously analyzes the
electronics for proper operation. If the watchdog detects a failure, one of the codes in
Table 3.3 will appear on the LCD.
The error codes can appear on the LCD when batteries are first installed,
during normal operation or if the unit is subjected to shock. In some cases, an
additional digit is used in the error code to supply additional information. For
example, the error code 6 and 7 are followed by another digit listed as (N) in Ta-
ble 3.2. The error code 65 would indicate that a key is stuck and this key is the
Silence key.
In addition to supplying visual error codes, the audio device will beep a
number of times to indicate the general error in case the display is not functional.
Note: To reset the watchdog error code, remove one battery for 5 seconds and re-
place. If the error persists, contact your local representative or Teledyne for as-
sistance.
Table 3.2 Error Codes
Error Code Audio Beeps Error
Indeterminate 2 The watchdog timer has timed out indicating
a serious software error
30 3 Analog output is different from the expected
value. May indicate a shorted or over-loaded
analog output or a failure of the analog to
digital converter or digital to analog conver-
ter circuit.