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Know the Simulator Probes

Updated: Nov 13, 2022

Tip 24: Knowledge of #duisimulator probes assists understanding of function & malfunction of thermistor, heater, and thermometer(s).

Many of our trials involve events that happened in Canadian winter conditions. Running evidentiary breath testing of subjects from a breath truck can be challenging for a qualified technician. Defence lawyers need to pay attention to whether or not the wet-bath simulator used in winter in a breath truck was being used properly. Pay close attention to:

  1. how each of the probes in the simulator respond to temperature variations (this blog entry)

  2. simulator heater response time (see another blog entry)

  3. manufacturer's specifications minimum operating temperatures - use of simulator in winter conditions (see another blog entry)

The Guth 2100 Dispersion Tube bubbles air pumped from the approved instrument during the cal check sequence. That air passes through the liquid alcohol standard and pushes alcohol vapour air up through the top of the simulator and is sucked into the approved instrument sample chamber. Hopefully, if there is a tight seal, correct temperature, and equilibrium, the contents of that alcohol standard air reflect the target value of the alcohol standard, usually 100 mg / 100 mls.

The Guth 2100 Agitator (Propellor) is continuously turning to ensure that the contents of the liquid below and the air above are all at the same temperature and at are their respective target concentrations (Henry's Law). A simulator with a propellor that is unreliable may not be maintaining the equilibrium.

The Heating Element turns on and off to heat the liquid contents of the jar to maintain 34.00 ± .05° C.. The heating element is controlled by the heater control that gets its information about current temperature from the micro controller attached to the Temperature Sensor probe which contains a thermistor (similar to a thermostat).

Guth 2100 probes
Probes on the author's Guth 2100

It is the responsibility of the Qualified Technician to record the temperature of the alcohol standard in the #duisimulator system at the time of any cal check to ensure that the alcohol standard vapour being pumped into the approved instrument sample chamber is at 34.0 ± .2° C (Henry's Law reflected in ATC Recommendations). If the temperature of the vapour pumped into the sample chamber is not within that temperature range, then the alcohol standard is NOT RELIABLE, and the subject breath test is NOT RELIABLE.

A good way to check and record that temperature would be for the QT to observe the Optional NIST Mercury Thermometer during the cal check and key that information into the approved instrument or record it in his or her notes.

The usual way, however, is for the QT to observe the temperature on the digital display or the RS232 interface display and report/record that temperature. Quaere: Where is that temperature information coming from? What temperature sensor sends the temperature information to the digital display or the RS232 interface? Is the same "precision thermistor" that controls the heater, also the probe that is the source of temperature information to the QT via the digital display or RS232 interface?

Please study the diagram at page 30 of 238 of the 2013 CFS Intoxilyzer 8000C Training Aid. With respect, the 2013 diagram of the "Guth Laboratories Model 2100 & Guth Laboratories Model 10-4D" is incorrect in its placement of the probes. The diagram at page 5-11 of the 2011 Training Aid is better. Please also see page 3 of the Guth Laboratories Inc. : "Model 2100 Simulator Operation Manual".

#probe #tip

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