Airflow Problems
For any airflow-related issue, begin with this general checklist before proceeding to specific symptoms.
General Airflow Checklist
- Internal Tubing: Confirm that all tubes inside the instrument are securely connected. After maintenance, tubes leading to the preconditioning unit at the top are often forgotten.
- Flow Sensors:
- Ensure flow sensors are installed in the correct orientation with the arrow indicating flow direction.
- Ensure all flow sensors are in their correct places and not switched with each other.
- Check that the correct signal cables go to the correct flow sensors.
- External Flow Meter Check (if available):
- Using a flow meter (e.g., TSI 4000 series), compare the actual flow rates with the values displayed in the measurement software. Note that the software shows volumetric flow rates, not corrected to STP conditions.
- Measure the sample flow rate at the instrument's exhaust.
- Measure the sheath flow rates by disconnecting the tubes leading up to the preconditioning unit and measuring flow coming from the sheath filters.
Fluctuating Flow
Symptom: The standard deviation of a flow sensor signal is abnormally high.
Solution: In addition to the general checklist, verify that the instrument's inlet is not exposed to strong wind, which can cause flow fluctuations.
Flow Too Low / Control Signal at Maximum
Symptom: The blower control signal is at its maximum, but the flow rate reported by the sensors remains below the target value. The system cannot increase the blower speed further.
Solution: After completing the general checklist, check for any obstructions in the airflow path. Ensure all tubing and electrical connections to the blowers are intact.
Flow Too High / Control Signal at Minimum
Symptom: The blower control signal is at its minimum, but the flow rate reported by the sensors remains above the target value.
Solution: After completing the general checklist, ensure all tubing and electrical connections to the blowers are intact.