Output Queue General Information

The Output Queue uses an optical sensor to verify that bleach and deactivation buffer are dispensed correctly.

The sensor assembly is installed in the top part of the Output Queue injector housing. The injector passes through an opening in the sensor assembly. The sensor assembly consists of two sensors and two emitters attached to a small PCB. The injector assembly tubing extends down into the injector. The injector contains four small windows through which infrared (IR) light passes.

The IR generated by the emitter passes through one window, the injector tubing, and out the opposite window to the sensor. The amount of IR that passes through the injector varies with the presence of liquid in the tubing.

Prior to an injection, the fluid in the injector tubing will not extend down to the area adjacent to the dispense verification sensor. After the dispense, a pullback occurs where the peristaltic pump briefly pumps in the opposite direction so that the fluid in the tube is again pulled up above the sensor level. This functionality allows dispense verification.

The sensor signal contains three distinct time regions: initial air (from the previous pullback), liquid dispense, and final air pullback.The signal is analyzed in each region to determine if the signal substantially matches the expected air/liquid signal. Small signal discrepancies are allowed, but larger discrepancies will generate an error. The specific region parameters and the acquired sensor signal for each dispense are logged in the Output Queue.curve file.

The air/liquid threshold value is determined by sensor calibration that is performed as part of the system Full PrimeOperation of pumping fluid through tubing to ensure proper and consistent fluid delivery (remove air from the tubing, etc.). routine.

The OLV system incorporates a liquid/air sensor near the injector orifice. Each dispense is followed by an airgap pullback. This pulls air back up past the sensor after each dispense. Therefore, the subsequent dispense starts with air in the tubing in front of the sensor.

The sensor signal for a good dispense is composed of the following phases:

1. The process starts a high signal (indicating air).
2. The signal transitions to a low signal (indicating liquid) as fluid is dispensed.
3. The signal remains low as the pullback begins.
4. The signal finally transitions to a high signal (air) as the air/liquid interface is drawn up past the sensor.

The Output Queue Process Control algorithm splits the air-liquid-air signal into three distinct regions. These regions are each defined by the following parameters:

• Start point
• End point
• Criteria (air or liquid)
• Minimum number of points required to meet the criteria

A threshold defined during sensor calibration, as part of a Full Prime procedure, is used to determine if each data point is considered as air or liquid. The threshold calculation sets the threshold at 1/3.5 of the way from the liquid value to the air value.

For a dispense to be considered good, the following conditions must be met:

• Region 2 check passes (this is the liquid phase check)
• Region 1 and/or 3 passes (these are the initial and final air pullback check)

The Non-Deactivated waste message will only appear to the system operator after four dispense failures in a row or six failures out of 20 dispenses.

The specific region parameters and the acquired sensor signal for each dispense are logged in the Output Queue.curve file. Sensor ID 0 corresponds to Deactivation Buffer and Sensor ID 1 corresponds to Bleach.

Typically, the process control system will generate failure flags when the system is dispensing air instead of liquid. This may be observed in the curve file data as Region 2 failures. In this case, the system should be inspected for the following conditions:

• An empty bleach or buffer bottle
• A disconnected bleach or buffer bottle
• A loose fitting in the fluid line from the bottles to the injector
• A damaged fitting or tubing in the fluid line from the bottle to the injector
• Kinked or crushed tubing in the fluid line from the bottle to the injector

  Note — This tubing is very thin-walled and can easily kink and occlude, particularly when routed through grommets and clips.

• Air or occlusion in fluid line from the bottles to the injector
• Old or worn peristaltic pump tubing

If the injector is actually dispensing properly and the failure is a false flag due to a problem with the process control system, then the system should be inspected for the following:

• Wet or damaged process control PCB in the Output Queue injector mount assembly
• Damaged or unplugged process control cable in the Output Queue (from the main PCB to the process control PCB)
• Poor quality of the air/liquid meniscus in the injector tubing during pullback (droplets left behind on the inner wall of the tubing in front of the sensor)

If the system has an Output Queue process control system failure, this failure may occur while performing a Full Prime because the process control system is calibrated during a Full Prime and is used to check to be sure that the bottles are correctly connected during a Full Prime. The process control system is not exercised during a Mini Prime.