Test equipment oxygen analyzers

Teledyne AX300: troubleshooting and error codes

The ServiceForge knowledge base holds 17 documented symptoms for the Teledyne AX300, with 31 ranked causes, 19 diagnostic checks with test points and expected values, and 10 error codes. Each symptom below shows its causes and the first check; the rest is one connection away. Connect ServiceForge to your AI

Symptoms

Display flashing √ SENSOR alarm patient safety

Unit displays flashing √ SENSOR message with continuous audible/visual alarm

Ranked causes

1. Faulty sensor connection (common)
2. Sensor expired (common)
3. Sensor exposed to gas with less than 18% oxygen (occasional)
4. Sensor output fallen below usable level (occasional)

First check

Verify sensor cable connection integrity

Test point: Sensor connector and capture nut
Expected: Completely inserted, capture nut firmly secured

1 more check with pass and fail actions, 4 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Sensor will not read below 22% after 100% O2 calibration

Unable to achieve readings below 22% oxygen after calibration in 100% O2 environment

Ranked causes

1. Invalid calibration in 100% oxygen (common)
2. Exhaust tubing too short or gas flow rate excessive (occasional)
3. Room air enriched with excess oxygen above 21% (occasional)
4. Sensor defective or degraded (rare)

First check

Recalibrate in 100% dry oxygen

Test point: Calibration gas source
Expected: Valid calibration in 100% O2

1 more check with pass and fail actions, 4 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Oxygen reading fluctuates or appears incorrect

Displayed oxygen concentration reading is unstable, fluctuating, or does not match expected value

Ranked causes

1. Exhaust side restriction or sensor pressurization (common)
2. Humidified gas used for ventilation (occasional)
3. Blender miscalibration (occasional)

First check

Verify no exhaust restriction during calibration

Test point: Sensor exhaust tubing
Expected: No restriction; reading stable regardless of flow

1 more check with pass and fail actions, 3 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Unit displays √ SENSOR alarm with flashing display

Continuous audible and visual alarm with √ SENSOR message displayed

Ranked causes

1. Faulty connection between sensor and unit (common)
2. Expired or faulty sensor (common)
3. Oxygen concentration below 18% (occasional)

First check

Verify sensor cable connection to unit

Test point: Sensor connector
Expected: Fully seated and locked connection

2 more checks with pass and fail actions are in ServiceForge. Connect ServiceForge to your AI

Unit stopped working with alphanumeric characters on display caution

Unit ceases operation and LCD displays alphanumeric characters; watchdog circuit activated

Ranked causes

1. Poor battery connections or corroded contacts (common)
2. Expired or defective batteries (common)
3. Radio frequency interference (occasional)

First check

Inspect battery contacts for corrosion

Test point: Battery compartment contacts
Expected: Clean, bright contacts without corrosion

1 more check with pass and fail actions, 3 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

No display on unit caution

LCD display is blank or not illuminating

Ranked causes

1. Batteries expired (common)
2. Bad battery connections (common)

First check

Verify battery expiration and condition

Test point: Battery terminals and date
Expected: Fresh batteries within valid date range

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Sensor does not react to oxygen changes or readings unstable

Sensor output does not respond to oxygen concentration changes or readings drift unpredictably

Ranked causes

1. Water condensation on sensing surface (common)
2. Electrical interference from external sources (occasional)

First check

Inspect sensing surface for condensation

Test point: Sensor sensing membrane
Expected: Clean, dry sensing surface

1 more check with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

ADC circuit failure detected

Error code 5 displayed during POST (Power-On Self-Test)

Ranked causes

1. ADC circuit defect (rare)

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Alarm condition triggered below 18% O2 patient safety

Visual green light flashes and alarm buzzer activates when oxygen concentration falls below 18% (ISO 7767 standard)

Ranked causes

1. Oxygen concentration below 18% (unknown)

First check

Verify oxygen concentration at analysis point

Test point: Analyzer display
Expected: ≥18% O2

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

DAC circuit failure during automatic calibration

Error code 7 displayed; second digit indicates DAC failure type (0=Measurement, 1=High Test, 2=Low Test, 3=Offset Cal, 4=Gain Cal)

Ranked causes

1. DAC circuit defect during calibration (rare)

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Incorrect oxygen reading in breathing system patient safety

Oxygen measurements are inaccurate or erroneous when analyzing breathing systems with the AX300 analyzer

Ranked causes

1. Breathing system downstream of sensor produces backpressure or flow restriction (common)

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

New sensor responds slowly or drifts

Newly installed sensor exhibits slow response time or concentration drift

Ranked causes

1. New sensor requires warm-up time (common)

First check

Monitor sensor response after warm-up period

Test point: Oxygen concentration reading
Expected: Stable reading without drift after 1-2 hour warm-up

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Sensor fail or disconnect detected caution

Audible and visual alarm indicator activates when sensor fails or becomes disconnected from analyzer

Ranked causes

1. Sensor disconnected or failed (unknown)

First check

Verify sensor connection

Test point: Sensor connector
Expected: Firmly seated connection

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Slow oxygen response time in confined volumes

Sensor response time is degraded when measuring oxygen in incubators, hoods, tents or other confined gas chambers

Ranked causes

1. Flow diverter installed on sensor in confined volume applications (common)

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Stuck key alarm activated caution

Alarm triggered when alarm silence key held down for extended duration; can only be deactivated by removing batteries

Ranked causes

1. Alarm silence key held down too long (occasional)

First check

Release alarm silence key if held depressed

Test point: Alarm silence key
Expected: Key released

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Stuck key detected

Error code 6 displayed; second digit indicates which key is stuck (1=Batt, 2=Cal, 5=Silence, 8=Key Lock)

Ranked causes

1. Mechanical key switch failure or debris (occasional)

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Unit displays √ SENSOR alarm for low oxygen concentration patient safety

Alarm indicates oxygen concentration below 18% threshold

Ranked causes

1. Gas supply oxygen concentration below 18% (common)

First check

Verify oxygen supply concentration

Test point: Oxygen source
Expected: Oxygen concentration at least 18%

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Error codes

Code	Meaning	Trigger	Severity
`30`	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 converter circuit.	Watchdog detects analog output mismatch during operation	error
`5`	Stuck key detected	Keyboard mechanism stuck during power-on self-test	warning
`5`	ADC circuit failure during POST	Power-on self-test detects ADC circuit malfunction	critical
`50`	ADC circuit failure during power-on self-test	Analog to digital converter fails self-test at power-on	critical
`6`	Stuck key detected	Key press detection circuit identifies stuck key	error
`6 or 7 + digit`	Stuck key error; additional digit (N) identifies which key	Watchdog detects key stuck condition	warning
`7`	Digital to analog converter (DAC) circuit calibration failure	Automatic DAC calibration fails during power-on self-test	error
`7`	DAC circuit failure during automatic calibration	Automatic calibration process detects DAC malfunction	critical
`Indeterminate`	The watchdog timer has timed out indicating a serious software error	Watchdog circuit detects failure during operation or after shock	error
`√ SENSOR`	Faulty connection between sensor and unit, expired or faulty sensor, or oxygen concentration below 18%	Continuous audible and visual alarm with √ SENSOR message display	error

Likely causes and actions for each code are in ServiceForge. Connect ServiceForge to your AI

Community

0 fixes logged by technicians through their AI, with outcomes, for this model.

ServiceForge knowledge base record. Field-unverified unless technicians confirmed it. A teaching summary of the record, not a service manual. Export 2026-10-14.