© 2019 Allbiss Lawdata Ltd.

This site has been built by Allbiss Lawdata Ltd. All rights reserved. This is not a government web site.

For more information respecting this database or to report misuse contact: Allbiss Lawdata Ltd., 303-470 Hensall Circle, Mississauga, Ontario, Canada, L5A 3V4, 905-273-3322. The author and the participants make no representation or warranty  whatsoever as to the authenticity and reliability of the information contained herein.  WARNING: All information contained herein is provided  for the purpose of discussion and peer review only and should not be construed as formal legal advice. The authors disclaim any and all liability resulting from reliance upon such information. You are strongly encouraged to seek professional legal advice before relying upon any of the information contained herein. Legal advice should be sought directly from a properly retained lawyer or attorney. 

WARNING: Please do not attempt to use any text, image, or video that you see on this site in Court. These comments, images, and videos are NOT EVIDENCE. The Courts will need to hear evidence from a properly qualified expert. The author is not a scientist. The author is not an expert. These pages exist to promote discussion among defence lawyers.

Intoxilyzer®  is a registered trademark of CMI, Inc. The Intoxilyzer® 5000C is an "approved instrument" in Canada.

Breathalyzer® is a registered trademark of Draeger Safety, Inc., Breathalyzer Division. The owner of the trademark is Robert F. Borkenstein and Draeger Safety, Inc. has leased the exclusive rights of use from him. The Breathalyzer® 900 and Breathalyzer® 900A were "approved instruments" in Canada.

Alcotest® is a registered trademark of Draeger Safety, Inc. The Alcotest® 7410 GLC and 6810 are each an "approved screening device" in Canada.

Datamaster®  is a registered trademark of National Patent Analytical Systems, Inc.  The BAC Datamaster® C  is an "approved instrument" in Canada.

Bandwidth of Filters Changes Over Time

January 11, 2018

Purpose:

 

To explain the basic methodology of IR quantitative analysis using an approved instrument.

To explain calibration.

To explain the function of the linearizer.

To explain drift over time.

To explain calibration curve.

 

The pencil is the sample in the sample chamber.

 

The paperclips are the instrument's electronic response to the transmittance of IR light through the sample chamber. An electrical signal is produced by the detector at the end of the sample chamber that has a relationship to transmittance.

 

The instrument has been calibrated at the factory such that the calibration curve recorded in the instrument's calibration software settings says 4 paperclips = 2 gms and 2 paperclips = 1 gm.In other words, 4 paperclips of electronic response in the detector is made to be equal to 1 gm in indication. That making of a relationship is the calibration of the instrument at the factory during a manual tweaking (5000C) or an auto calibration sequence (8000C or 5000EN).

 

The circuit that does that is called the linearizer.

 

That relationship established with a screwdriver on a 5000C or a software adjustment on the 8000C does not change until the next re-calibration at the factory or the Canadian authorized Service Centre.

But what if the electronic response changes "over time" because the filter changes colour or gets dirty? Perhaps the bandwidth changes. Perhaps the properties of the filter and the optical system change "over time". What happens if the IR light bulb dims?

 

The calibration curve becomes wrong. It needs changing. The instrument needs re-calibration. The adjustment require may be non-linear - it may be a different amount at each of 50, 100, 150, 200, and 250 mg/100mls. The new calibration curve relative to the old calibration curve may be a movement up, down, left, right, a stretch, or a rotation on any axis.

 

 

 

 

Please reload

If you are a Canadian criminal defence lawyer and you wish to learn more about cross-examination on these issues, we suggest that you visit the Members page at www.impaired-driving.com and enroll in the three online courses that are described therein. Once you have completed the three online courses, you can apply to become a full Member at that site, and if you are accepted for membership, you will have access to the much more extensive Members Only Blog at that site, as well as  additional international resources, links, and materials.

If you are a Canadian criminal defence lawyer and you wish to learn more about cross-examination of Drug Recognition Experts we recommend that you attend an online or recorded session at  https://www.impaired-driving.com/dre-tutorial.

Featured Posts

OIML R126 is the International Standard for Evidential Breath Analyzers

August 14, 2018

1/5
Please reload

Recent Posts
Please reload

Archive
Please reload

Search By Tags