Which branches make up a hematology analyzer fluidic system?
Arrows indicate task relationships, not that every component is connected in series in one tube. Check valve positions, pump wetted boundaries and operating states for each branch.
Typical branches handle whole-blood sampling, diluent metering, channel-reagent addition, detection-fluid supply, cleaning and waste removal. This sequence describes functional relationships; channel operations may be interleaved by the instrument scheduler.
With a metering valve, first fill the metering chamber completely, then isolate and transfer its fixed volume; filling, sealing and residue also affect delivery. With pump-displacement metering, consider pump stroke, probe tip, tubing and isolation interface as one system. Blood passing through the sampling probe does not necessarily enter the pump chamber: system-liquid drive and direct sample contact require different materials and cleaning coverage.
Common product roles and application guides
Assign a clear task to each component before combining branches. A shear-type metering valve separates a volume using its metering chamber; an ordinary multiport rotary valve primarily selects paths. Define their functions and acceptance checks separately.
| Product | Task in a hematology analyzer |
|---|---|
| Piston pump / syringe pump | Drive sampling or meter diluent and channel reagents; configure for direct liquid contact or system-liquid drive |
| Liquid diaphragm pump | Liquid replenishment and cleaning-fluid supply, combined with reservoirs, pressure stabilization or point-of-use metering |
| Gas–liquid diaphragm pump | Remove wash fluid and aerated waste, accommodating simultaneous inflow from multiple branches |
| Multiport rotary valves / solenoid valves | Select sources, channels and cleaning paths; open and close branches |
| Sampling probes, tubing and fittings | Provide sampling and connections while controlling residue, inlet resistance and assembly variation |
| Bubble and pressure detection | Provide phase-specific abnormality signals, interpreted by the instrument with valve position, sample and action |
Operating conditions to confirm at each stage
Provide the following information separately for each channel. A shared liquid source reduces components, but replenishment or pressure fluctuations can affect several channels simultaneously; dedicated branches require more space, tubing and maintenance points.
| Stage | Conditions determining configuration |
|---|---|
| Whole-blood sampling | Interval from mixing to aspiration, dose, minimum usable remaining volume, open-tube or piercing mode, liquid-contact arrangement |
| Dilution and channel reagents | Actual dose per branch, serial-dilution sequence, mixing location and processing time |
| Detection-fluid supply | Sample and sheath-flow requirements, detection-window duration, permissible pressure and flow fluctuations |
| Cleaning and waste removal | Surfaces requiring cleaning, cleaning agent, peak simultaneous drainage and blank-recovery requirements |
| Recovery from abnormalities | Sensor locations, sample association, steps that permit retry and termination conditions |
Sampling: retain mixing and low remaining sample-volume conditions in evaluation
Cell settling makes sampling time and position important to sample representativeness. Arrange mixing according to sample and assay requirements, then keep the interval from mixing completion to aspiration consistent. A mode for low remaining sample volume must account for container-bottom geometry, probe descent position and available sample volume; lowering the probe further to obtain liquid may increase liquid carried on its outer surface.
If aspiration lags, first check probe contact with the container wall, inlet resistance, bubbles and sealing, then consider reducing aspiration speed or extending the wait; extra waiting consumes cycle time. Clots or abnormal resistance should trigger the instrument's corresponding exception procedure. Simply increasing suction may carry the problem into downstream channels.
Further technical reading
Dilution and lysis: actual ratios in each counting channel
Red-cell, white-cell and other channels have different processing objectives; lysis, staining and dilution sequences must match the specific method. First measure sample and reagent volumes delivered at the mixing location separately, then check mixing and processing time, and finally assess counting and differentiation results.
The same total volume can contain different sample proportions, so an acceptable total still requires checking each branch's contribution. Serial dilution also requires recording the preceding stage's mixing state and the position of secondary aspiration. Where sample and diluent doses differ greatly, prioritize separate metering capacities. Sharing a metering unit reduces hardware but increases flushing and sequential scheduling time.
Further technical reading
Detection channels: sheath flow, apertures and fluid renewal
The detection structure determines whether sheath flow is needed. Impedance counting can also use sheath-flow focusing: the Sysmex DC sheath-flow approach guides diluted cells through the center of the aperture and then toward the drain. List sample flow, focusing flow and drainage separately rather than deciding whether sheath fluid is needed solely from the label 'impedance' or 'optical'.[2]
When a syringe pump supplies liquid during a detection window, usable capacity must cover that window and necessary auxiliary actions. If replenishment interrupts flow, schedule it between measurements. For longer continuous supply, compare reservoir-based pressure stabilization or alternating supply and check handover fluctuations. Source-supply pumps and point-of-use flow control serve different tasks; selection must account for the detection channel's actual resistance.
Further technical reading
Cleaning and waste removal: restore the channel for the next sample
The inner and outer sampling-probe surfaces, mixing chamber, aperture or flow cell each need adequate cleaning coverage. For inadequate supply, first check installed resistance and flow splitting between branches. For delayed drainage, check the waste circuit, foam and container state. Increasing supply also increases waste-removal load; match pump capacity to peak simultaneous inflow.
After blockage, use the model's permitted flushing or backflushing procedure and check channel flow, blank and specified quality controls before resuming samples. Judge cleaning success by restored channel performance, not merely by pump operation or a cleared alarm.
Further technical reading
State identification: distinguish blockage from air aspiration
Establish separate pressure baselines for sampling, reagent addition, counting and cleaning. Inlet obstruction, an exhausted liquid source, bubbles, valve changes and leaks can all alter the trace; combine the timing of changes with bubble or level signals to narrow the cause.
The instrument control system associates sensor outputs with sample ID, current channel and step. Distinguish commanded volume, stroke-estimated volume and independently measured volume in records. If an abnormality occurs after partial aspiration or dispensing, preserve completion status before deciding to resample, remake that sample's diluted mixture or terminate the determination.
Further technical reading
Explore configurations through product application guides
For multiple metering units, compare channel configurations in the FOREACH HMD series. For one metering unit selecting multiple liquid sources sequentially, compare the HLD syringe and multiport rotary-valve combination. Multiple metering channels and multiport routing are separate dimensions; more ports do not automatically create more branches that can meter simultaneously.[3][4]
Compare piston and syringe pumps by minimum dose, auxiliary strokes, replenishment timing and wetted path. Select cleaning and waste pumps by installed flow and gas–liquid conditions. For valves, prioritize shared-path residue; for probes and fittings, cleaning coverage and dead volume. Model-specific capacity and materials must suit the actual reagents, cleaning agents and operating sequence.
- View the IVD product–task matrix
- Piston pumps in hematology analyzers
- Syringe pumps in hematology analyzers
- Diaphragm pumps in hematology analyzers
- Multiport rotary valves in hematology analyzers
- Sampling probes in hematology analyzers
- Bubble and pressure sensing in hematology analyzers
- Tubing and fittings in hematology analyzers
Validate the complete cycle through application results
Record metering, ratios, detection flow and recovery separately, then look for relationships within the same test batch. Acceptance targets are defined by the corresponding method and project.
| Stage | Actual measurement | Priority areas to investigate |
|---|---|---|
| Sampling | Delivered volume at normal and low remaining levels; carryover from high to low samples | Mixing, air aspiration, clots and residue inside and outside the probe |
| Dilution processing | Delivered volume by branch, mixing and processing time, assay results | Capacity configuration, shared residual liquid and aspiration position |
| Detection-fluid supply | Flow, pressure, bubbles and counting blank during the detection window | Replenishment handover, focusing-fluid supply, aperture or flow cell |
| Cleaning recovery | Peak waste removal, blank after flushing and first sample after recovery | Flow splitting, foam, residual liquid and maintenance assembly |
| Abnormality identification | Phase-specific detection and false alarms, response time and sample association | Baseline differences, sensor position and control state |
Common selection and recovery questions
Why can counts remain abnormal when sampling repeatability passes?
Continue by checking actual sample-to-reagent ratios, mixing and processing time, then flow, bubbles and channel blank during detection. Repeatability describes only the consistency of one action; persistent delivery bias or channel residue can still affect results.
Does increasing syringe-pump capacity guarantee continuous sheath-fluid supply?
Greater capacity can extend a single supply window while changing stroke utilization and replenishment scheduling. Calculate the required supply volume first, then check whether replenishment fits between measurements. If no gap is available, evaluate alternating or pressure-stabilized supply and its switching fluctuations.