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Calibrating Thermal Imagers with a 418X

Tech Notes

          

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Title: Calibrating Thermal Imagers with a 418X                                                   

Created:  14 Jan 2013

Last Revised:

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Applies To:  4180 and 4181

 

Problem Description:  Can I calibrate a Thermal Imager with a 418X?

 

Resolution/Work Around:   We cannot provide the specific information on calibration or how we perform the process on the production line due to intellectual property reasons and US Export Compliance regulations, however, we can provide some basic tips for checking the temperature measurement accuracy on the Ti10 and Ti25.

 

The official specification of the imager is at 30 degrees C target temperature, and assuming they have a Hart 4181 which is not specified to be calibrated below 35C… but you still should be able to get good enough results overall.

 

  1. Set the 4181 to .95 emissivity, and allow it to stabilize at 35C.
  2. Power up camera and allow it to stabilize for at least 10 minutes.
  3. Set emissivity in camera to .95.
  4. At a distance of approximately 17‐20 inches from the blackbody surface, focus sharply on the plate, not the aperture. (Focus position is critical.) The imager should be 90 degrees (perpendicular) to the plate surface.
  5. You can repeat for 100C if you wish… but there is an unpublished ambient temperature de‐rating that may cause readings to vary slightly the farther away from 30C you get. When this is done, the imager should be within “plus or minus 2 degrees C or 2%, whichever is greater” for the Ti25 and “plus or minus 5 degrees C or 5%, whichever is greater” for the Ti10.

Another way to check the temperature measurement is with boiling water at 100C or an icewater bath at 0C. (and it is less expensive than a Hart 4181!) In the unlikely event lens cleaning is required:

In the unlikely event lens cleaning is required:

 

  1. Use a photography air bulb to gently blow debris or dust from the lens area. (DO NOT USE compressed air, nitrogen, or carbon dioxide which may cause a temperature drop and “thermally shock” the lens.)
  2. If you do not have a photography air bulb, you can also use a photography lens brush to gently brush off the surface of the lens.
  3. If the lens is still not cleaned sufficiently, or there are fingerprints or residue present, you can clean the lens with the following procedure:
    1. Create a light soap solution with a few drops of a mild liquid soap (like dish soap) in a small container of warm water.
    2. Dampen a clean micro‐fiber cloth in the solution.
    3. Gently wipe the surface of the lens with this cloth, but do not apply significant pressure.
    4. Allow to air dry or gently pat the surface of the lens with another, clean, but dry micro‐fiber cloth.

Keep in mind that you should very rarely need to clean lenses if the cameras are taken care of, and stored properly. Dust particles will usually not cause any deterioration of image quality or performance.  Fingerprints also do not cause major issues because they are not in the focal plane of the target objects.  However, fingerprints contain oils, which if left on the surface of the lens, can cause the special coatings to deteriorate. If the coating deteriorates or is significantly scratched, there will eventually be deterioration in performance.

 

DO NOT use any kind of solvents or commercial cleaners to clean your lenses, (No acetone, alcohol, ammonia, benzene, etc.) as these could damage both the coating and the sealants in the lens assembly.

 

DO NOT immerse the camera or lenses in any liquids, as they are not waterproof, only moisture

resistant per the IP54 testing standards.

 

DO NOT use dirty or heavy rags to clean the lenses, as these can result in scratching.

 

The cases and holsters can be carefully cleaned with light soapy solution and a standard, damp cleaning cloth of some type…. Just like Fluke’s other meters.

 

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