CMLA Laboratory Equipment Operation & Maintenance 4 — Questions and Answers
Question 1: What is the purpose of the condenser on a compound light microscope?
- To magnify the image
- To focus and direct light onto the specimen (Correct answer)
- To protect the objective from immersion oil
- To adjust the eyepiece distance
Correct answer: To focus and direct light onto the specimen
The condenser collects and concentrates light from the illuminator and focuses it onto the specimen for optimal image brightness and resolution.
Question 2: A urinalysis analyzer reports 'cuvette dirty' error. What is the correct response?
- Ignore the error and proceed with testing
- Clean the cuvette per manufacturer protocol and run a system check (Correct answer)
- Replace the entire reagent cartridge
- Restart the analyzer without cleaning
Correct answer: Clean the cuvette per manufacturer protocol and run a system check
A dirty cuvette causes optical errors; cleaning per manufacturer instructions restores accurate photometric readings.
Question 3: Which safety feature prevents a centrifuge lid from being opened while the rotor is spinning?
- A rotor lock bolt tightened by the operator
- An interlocking lid mechanism tied to the rotor speed sensor (Correct answer)
- A warning sticker on the lid
- A manual brake applied by the operator
Correct answer: An interlocking lid mechanism tied to the rotor speed sensor
Modern centrifuges use an electronic interlock that prevents lid opening until the rotor has fully stopped, preventing injury from the spinning rotor.
Question 4: When performing quality control on a coagulation analyzer, two consecutive QC results fall outside the 2SD warning limit on the same side. This pattern represents which Westgard rule violation?
- 1-2s warning rule
- 2-2s rule (Correct answer)
- R-4s rule
- 10-x rule
Correct answer: 2-2s rule
The 2-2s rule is triggered when two consecutive QC results exceed the same 2SD limit, indicating a possible systematic error.
Question 5: Before storing a pH electrode overnight, it should be placed in:
- Distilled water only
- pH 7 buffer or electrode storage solution (Correct answer)
- Dry storage in a capped tube
- 70% isopropyl alcohol
Correct answer: pH 7 buffer or electrode storage solution
Electrodes must be kept moist in pH 7 buffer or storage solution to prevent the reference junction from drying out and losing function.
Question 6: What is the function of the decontamination cycle at the end of run on an automated blood cell counter?
- To calibrate the cell counting aperture
- To flush the fluidic system with cleaning solution and prevent carryover or clogging (Correct answer)
- To print a final QC report
- To reset reagent volume counters
Correct answer: To flush the fluidic system with cleaning solution and prevent carryover or clogging
The end-of-run decontamination cycle removes residual blood and reagent from the fluidics, preventing clogging and biohazard contamination between sessions.
Question 7: An incubator temperature log shows a 1°C drift upward over one week. Which action is most appropriate?
- Document and continue monitoring without action
- Investigate the cause, recalibrate or service the unit, and assess any affected cultures (Correct answer)
- Increase the setpoint to compensate for the drift
- Switch to a different incubator without documentation
Correct answer: Investigate the cause, recalibrate or service the unit, and assess any affected cultures
A consistent temperature drift indicates a calibration or mechanical issue that requires investigation and service before further use.
CMLA Laboratory Equipment Operation & Maintenance 4
What is the purpose of the condenser on a compound light microscope?