Theory And Design Of The Alco-Sensor Fst - Intoximeters Alco-Sensor FST Operator's Manual

Alco‐Sensor FST®
The Alco‐Sensor FST® has an automatic sampling system designed to ensure that a sample of
deep lung air is obtained and analyzed. In order to trigger automatic sampling the subject must
blow with a minimum flow rate, must produce a minimum breath volume and blow for a
minimum duration. When the minimum flow rate is met a continuous tone will sound, the
head icon will stop flashing, the message Blow will disappear, and one of three progressive
dashes will appear to the right of the icon. If the subject continues to blow while exceeding the
minimum flow rate two more dashes will appear to the right of the head icon.
If the subject stops blowing before the sampling requirements have been met, one of the four
flow messages will appear and the device will re‐cycle to allow a second attempt to provide a
sample. After a very short wait the flashing head icon will reappear and the subject should be
directed to blow again. The device will allow up to three attempts to provide a breath sample
for each test sequence.
When all the sampling requirements are met there will be an audible click and the sample will
be accepted and analyzed. The analysis of the breath sample usually takes less than 10
seconds to complete and there are three possible results:
Result displayed on screen
Digital Numerical Reading
WARN
FAiL
The test result will be displayed for about ten seconds and then the device will power off
automatically. Show the reading to the subject. You can recall the test result using the menu
function, LAST (see Alco‐Sensor FST® Menu Functions on page 17).
4.2 Theory and Design of the Alco‐Sensor FST®
The Alco‐Sensor FST® contains a fuel cell sensor and an electrically operated sampling system. A
pressure sensor in the device monitors breath flow and volume to determine when to capture a
breath for analysis. While a subject is blowing and when deep lung breath is reached the
sampling system is activated. A small, fixed volume of deep lung breath is drawn onto the
surface of the fuel cell, any alcohol present in the sample is oxidized, generating a current. The
resulting electric current is translated into a blood alcohol concentration and the result is
displayed on the Alco‐Sensor FST® in blood alcohol concentration units of milligrams of alcohol
in 100 milliliters of blood (mg%).
Display ‐ The display and the back light turn on when the device is powered ON. Various
commands and symbols appear on the display to direct the operator through the testing
procedure and alert the operator of improper testing conditions detected by the system.
Alco‐Sensor FST® Operator's Manual
BAC Level
0 to 59 mg%*
60 to 99 mg%
100 mg% or higher
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Operator's Manual
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2018‐12‐18