Pumps, valves, probes, fittings, tubing and sensing components for precise sample preparation, reagent handling and instrument fluidics.
Bubble and Liquid-State Detection in Analyzer Tubing
Application guide · Bubble detection
A bubble detector is useful only when its location and time window distinguish an intended air segment from a fault. Define the minimum event to detect, tubing and liquid optical behaviour, velocity and the controller action before setting a threshold.
Engineering example: a 2 mm-long bubble moving at 100 mm/s passes one sensing point in 20 ms. Detecting it requires adequate sampling and persistence logic; a 100 ms debounce would intentionally ignore that event.[1][2]
01Define the liquid, receiver and complete duty before selecting the component
Translate the analytical task into an engineering duty
Use case
Inputs to define
Decision supported
Empty-source detection
Continuous gas after expected liquid arrival
Stop before an invalid dose reaches the receiver
Random bubble detection
Minimum length and velocity
Observe short events without excessive false alarms
Programmed air gap
Expected position and duration
Treat as a valid segment, not a fault
02Calculate the working point and the margin the instrument really needs
Calculations to complete before prototype selection
Quantity
How to define it
Why it matters
Event duration
bubble length ÷ local velocity
Sets sample rate and filter window
Sensor location
distance/flow from fault source to decision point
Sets available response time
Tubing fit
OD, wall, transparency and mounting
Determines optical coupling
Use minimum, routine and maximum conditions rather than one nominal point. Include the first cycle after priming or idle, the lowest source level, the highest expected restriction and the actual receiving geometry. A nominal capacity, free-flow value or theoretical command increment is not an acceptance result.
03Map the task to a FOREACH configuration and the rest of the fluid path
04Program the full liquid cycle, including prime, wash and recovery
Learn liquid baseline→Open valid observation window→Filter and classify event→Stop/divert/retry as defined→Prime and confirm liquid→Resume only after recovery test
A complete method cycle is more than the active delivery step
The exact physical order and parallel actions depend on the instrument. Retain each state in the control and verification plan.
Record valve states, motion, dwell, sensor windows and rejected recovery cycles. This makes throughput and liquid consumption auditable and prevents a fast component movement from being reported as the complete analyzer cycle.
05Design abnormal-state diagnosis before the fault occurs
Observed result, likely mechanism and useful next action
Observed condition
Likely mechanism
Engineering response
False bubble alarms
Tube motion, foam or optical variation
Fix mounting and qualify liquid-specific threshold
Missed bubbles
Event shorter than filter or poor coupling
Increase sampling or change location
Bubble detected too late
Sensor downstream of decision point
Move upstream or add diversion capacity
The controller should distinguish a recoverable event from a result-invalidating event. A retry is useful only after the original cause has been removed and the liquid path has returned to a verified state.
06Accept performance where the liquid is actually used
Minimum qualification plan for the integrated channel
Result
Where or how to measure
Acceptance question
Detection limit
Known gas segments across operating speeds
Required event is detected
False-alarm rate
All intended liquids and motions
Supports unattended operation
Recovery
Empty source and random-bubble challenges
Controller prevents acceptance of invalid liquid
Test the exact liquid and complete wetted path at minimum, routine and maximum conditions.
Separate first-cycle, steady-state and post-idle results; do not average away recovery behavior.
Challenge the relevant fault and confirm the controller prevents an invalid result from being accepted.
Retain the configuration, software sequence, consumables and receiving-position result together as the qualification record.
