BS-240
Benchtop, fully automated discrete clinical chemistry analyzer with an optional ISE module, used in small and mid-size hospital and private laboratories for routine biochemistry.
About 880 manual-derived records (roughly 690 fault and 200 maintenance entries from the service and operator manuals); no field cases.under engineering review
Architecture
Sample/reagent probe and arm
A single probe arm moves horizontally and vertically to aspirate sample and reagent and dispense them into the reaction cuvettes. It carries capacitive liquid-level detection, a collision sensor and a pressure-based clog detection circuit. Most mechanical alarms on this analyzer come from here: sensor or cable faults, loose drive belts, wrong position parameters, clots and clogs.
Syringe and fluidic system
Precision syringes meter the sample and reagent volumes, and further syringes and pumps drive the probe interior wash and cuvette washing. Valves, tubing, DI water and diluted wash solution tanks with float sensors, and high- and low-concentration waste lines complete the circuit. Air bubbles, leaking seals, worn plungers and kinked tubes show up as dispensing errors, poor precision and carryover.
Sample/reagent carousel and refrigeration
A carousel holds sample tubes, reagent bottles and fixed positions for wash solution and saline, with a bar code reader for samples and reagents. The reagent area is refrigerated by a cooling unit with a heatsink and fan. Dusty heatsinks and failing fans cause reagent refrigeration temperature alarms; reader faults show as bar code communication or scan errors.
Reaction carousel, mixer and temperature control
Reactions run in cuvettes on a heated reaction carousel, with a separate mixer to stir sample and reagent. Water, wash solution and reagents are pre-heated. Temperature alarms come from room temperature out of range, sensors, heaters, thermal protection switches or lost parameters; movement errors come from home sensors, belts, jams, drive boards or motors.
Cuvette wash station
The cuvettes are washed and dried automatically between tests by a multi-nozzle wash station driven by its own syringe and pumps. A dirty or blocked wash station leaves residues that show up as cuvette blank and water blank errors and carryover.
Photometer
A lamp, optics and a photoelectric collection board measure absorbance through the cuvettes at several wavelengths. Lamp ageing or poor seating, contaminated cuvettes and gain problems give low light intensity, cuvette blank out of range and dark current errors. The lamp is a routine replacement item.
ISE module (optional)
The ion-selective electrode module measures electrolytes with its own electrodes, reagent pack, peristaltic pumps, air bubble detector, 24 V supply board and communication link to the analyzer. Typical problems are purge failures, air in the calibrator lines, electrode slope and drift errors, and loss of communication.
Control electronics and operating PC
Control and drive boards in the analyzing unit run the motors, sensors and heaters, and an external PC runs the operating software, database and LIS link. Some alarms (CPU busy, database errors, abnormal exit) are purely software-side and are cleared by restarting the software and analyzing unit in the right order.
Faults and how to find them
Probe vertical or horizontal movement error, or 'probe collides with an obstacle' alarm.reference
- Real obstacle (tube cap, misplaced bottle) in the probe path
- Collision sensor not seated after the probe was refitted
- Dust on the position sensor or sensor/cable failure
- Loose drive belt or belt pulley
- Incorrect probe position parameters
- Drive board or motor failure
- Look for an obstacle and for tubes or bottles in the wrong position
- Check the probe is mounted vertically and that the collision sensor is correctly engaged
- Inspect the probe cable for fraying, loose connection or short
- Clean the position sensor and check the belt and pulley tension
- Check and readjust the probe position parameters
- Replace sensor or cable, then drive board, then motor
Remove the obstacle or tighten the belt; recalibrate positions after any probe or arm work. Replace electronics only after mechanics and positions are confirmed.
Probe level detection failed, insufficient sample or reagent, or 'sample contains air'.reference
- Genuinely insufficient sample or reagent, foam or bubbles on the liquid surface
- No DI water or a fault in the probe's fluidic (hydro) path
- Level detection board or its cable
- Incorrect vertical position limit for the probe
- Check volume and remove foam or bubbles; rerun
- Confirm DI water supply and that the probe flushes normally
- Inspect the level detection cable and board connections
- Check the probe's vertical limit position parameters above the carousels
Most cases are pre-analytical. If it repeats on good samples, check the fluidics, then the level detection board and cable, and correct the position parameter.
Probe clog detection alarm, sample with clots or fibrin, or 'probe is clogged during cleaning'.reference
- Clots or foreign matter in an incompletely prepared sample
- Partially blocked probe
- Air bubbles in the clog detection pressure line
- Probe interior wash tubing, pump or valve fault
- Clog detection board or pressure sensor
- Check sample preparation (centrifugation, clots)
- Clean the probe with diluted wash solution; remove and unclog it if needed
- Look for bubbles in the clog detection pressure path
- Check interior wash tubing, pump and valve
- Only then check the clog detection board and pressure sensor
Clean or unclog the probe and purge air from the pressure line; replace the clog detection board or sensor only if the fluidic causes are excluded.
Dispensing errors, poor precision or bubbles visible in the sample or reagent syringe.reference
- Air in the syringe or tubing
- Leak at the syringe tee or plunger guide cap
- Loose syringe mounting screws
- Worn plunger assembly
- Inspect the syringes for bubbles and leaks
- Check the tee and plunger guide cap for leaks
- Check the locking screws under the syringe are tight
- Run the bubble removal procedure and repeat precision checks
Remove the air, reseal leaks and tighten the mounting. The plunger assembly is a wear part: the maintenance data call for replacement after about 100,000 syringe cycles.
Mixer, reaction carousel, or cuvette wash syringe movement error; failure to find the home (zero) position.reference
- Home sensor or sensor cable fault
- Loose belt or pulley
- Mechanically jammed assembly
- Drive board fault
- Motor fault
- Switch the analyzing unit off and on and try to recover the failure
- Check the assembly moves freely by hand with power off
- Check and tighten belts and pulleys
- Check the sensor and its cable
- Swap drive board, then motor
Clear the jam or tighten the belt; replace sensor or cable, drive board or motor in that order.
Water tank empty, insufficient diluted wash solution, or high-concentration waste tank full, while the tanks are actually at a normal level.reference
- Stuck or faulty float sensor
- Broken wiring or poor contact between the float and the main board
- Main board input fault
- Confirm the actual level in each tank
- Run the float check and move the float by hand
- Check float wiring and connectors to the main board
Replace the float sensor or repair the wiring; the main board is last on the list.
Temperature out of range alarm: reaction carousel, cuvette wash solution, DI water for cuvette washing, or reagent preheating.reference
- Room temperature outside the specified range
- Temperature sensor short or open circuit, or cabling
- Thermal protection switch open
- Heater failure
- Temperature control parameters lost
- Electromagnetic interference
- Reproduce the alarm and measure room temperature
- Check the sensor and its connections for shorts or breaks
- Check the thermal protection switch is closed and its connections are sound
- Measure the heater resistance at room temperature against the manual value
- Check the temperature control parameters
Correct the room conditions first; then replace the sensor, protection switch or heater as found, and restore parameters if lost.
Reagent refrigeration temperature out of range.reference
- Dust on the cooling heatsink and fan
- Cooling unit power supply
- Temperature sensor or cabling
- Lost parameters or interference
- Check the cooling unit is powered
- Clean the heatsink fan and dust screens
- Check the sensor and cabling
- Check the refrigeration parameters
Cleaning the heatsink and fan is the most common cure; otherwise replace the failed cooling component or sensor.
Lamp not turned on, light intensity too low, or absorbance readings drifting high.reference
- Lamp failed or aged
- Lamp not seated correctly or fixing screws not tightened after replacement
- Lamp cable disconnected
- Lamp power board not connected properly
- Analyzing unit power supply
- Photoelectric collection board
- Check whether the lamp lights
- Check lamp seating, screws and cable
- Check the lamp power board connection and supply
- Run the light intensity check across cuvettes
- Check the photoelectric collection board
Replace or correctly re-seat the lamp and then run the photometer checks. If the lamp is fine, work back through the lamp supply to the collection board.
Cuvette blank, water blank or R1 blank absorbance out of range.reference
- Contaminated cuvettes
- Cuvette overflow
- Empty cuvette position
- Poorly performing cuvette wash station
- Reagent problem (for R1 blank)
- Ageing lamp
- Inspect the cuvettes and run a water blank on each
- Check the wash station nozzles and tubing for blockage
- Check reagent condition and volume
- Check the light intensity
Clean the wash station, replace dirty cuvettes, and retest. Recurring blank errors after cleaning point to the lamp or the wash station fluidics.
Dark current too high, or photoelectric measurement period or data out of range.reference
- Photometer circuit gain too high
- Poor earth (ground voltage) at the installation
- Interference or poor contact between the photoelectric boards and the main control board
- Software error
- Restart the operating software, then the analyzing unit
- Run the dark current fluctuation test
- Check the ground voltage at the mains supply
- Check cables between the photoelectric boards and the main control board
Correct the earthing and connections; readjust photoelectric gain per the service procedure if the test shows it out of range.
ISE: purge A/B failed, or air in calibrator A or B lines.reference
- Electrode installed incorrectly or missing O-ring (leak)
- Blocked sample injection port or electrode path; salt buildup in the reference electrode
- Calibrator in the reagent pack exhausted
- Peristaltic or waste pump tubes aged or blocked
- Air bubble detector failed
- Reinstall electrodes and check every O-ring
- Rinse the sample injection port and electrode tubing with warm water
- Check the reference electrode for salt buildup
- Check reagent pack level and replace if exhausted
- Increase prime cycles; inspect and replace pump tubes
- Replace the air bubble detector if all else is fine
Most purge and air errors are fixed by reseating electrodes, cleaning the injection port and renewing pump tubes or the reagent pack.
ISE: slope out of range, electrode drift, voltage noise or voltage overflow.reference
- Electrode not installed correctly
- Electrode or reagent pack invalid or expired
- New electrode not yet stabilised
- Reference electrode at the end of its life
- Remove and reinstall the electrode
- Check expiry of electrodes and reagent pack
- After installing a new electrode, allow it to stabilise and run several calibrations before judging it
Replace the failed electrode or reagent pack. The reference electrode is a scheduled replacement item.
ISE unit does not respond, cannot be initialised, or reports command or communication errors.reference
- ISE 24 V power supply board
- ISE communication cable or connector pins
- ISE main control board
- Mismatched software version
- Check the ISE supply
- Check and reseat the communication cable and pins
- Confirm the software version matches the ISE module
- Swap the ISE control board last
Replace the supply board, cable or control board as found, or reinstall the correct software version.
Sample or reagent bar code reader errors (initialisation failed, communication error, buffer full).reference
- Transient communication error
- Reader fault
- Wrong bar code format or label
- Rescan the bar code
- Recover the failure and reinitialise the reader
- Reboot the analyzing unit
- Check the bar code settings and label quality
Usually cleared by reinitialising or rebooting; replace the reader if the error keeps returning.
Preventive maintenance
| Check the DI water tank level and tube connections | daily |
| Check the diluted wash solution container and tubing | daily |
| Check waste tubing and empty the high/low-concentration waste tanks | daily |
| Check the probe for leaks, stains and normal outflow; inspect tubes for kinks and leaks | daily |
| Check or replace the probe wash solution | daily |
| Check system, subsystem and calibration status before running samples | daily |
| Clean the probe exterior and the mixer to prevent carryover | weekly |
| Check cuvettes for contamination with a water blank on each cuvette | weekly |
| Clean the cuvette wash station and wash wells | monthly |
| Check light intensity by measuring the absorbance of several cuvettes | monthly |
| ISE: calibrate the peristaltic pump and the bubble detector | monthly |
| ISE: replace the reference electrode | every 6 months |
| Replace the syringe plunger assembly | after about 100,000 syringe cycles |
| Replace the water inlet filter and the diluted wash solution filter | per the analyzer's maintenance log reminder |
| Clean fans, heatsink fan and dust screens | when needed |
| Replace aged peristaltic pump tubes and ISE electrodes | when needed |
Parts worth keeping on the shelf
| Photometer lamp | Lamp ageing or failure stops all photometric testing; it is the routine wear item of the photometer. |
| Syringe plunger assembly and seals | Wear part with a cycle-based replacement; worn seals cause bubbles, leaks and poor precision. |
| Sample/reagent probe | Probes get bent in collisions or permanently clogged; a spare gets the lab running the same day. |
| Water inlet filter and diluted wash solution filter | Scheduled replacement items; blocked filters starve the wash system. |
| ISE peristaltic pump tubes | Aged tubes are behind most purge failures and air-in-calibrator alarms. |
| ISE reference electrode | Scheduled six-monthly replacement and a common cause of drift and slope errors. |
| Level/float sensor for the tanks | A stuck float gives false empty or full alarms that stop the analyzer. |
After any repair, run the manufacturer's full checkout and performance verification before the device goes back to patients.