Monday, August 22, 2011

Looking Down the Barrel of an Infrared- Part Two



Last week I talked about some of the potential issues for Emergency Responders re build up on the Fresnel lens system in an infrared temperature gun.  Smoke & ash from fires are one set of issues, and chemical extinguishing agents are another.  Chemical vapor residues from a chemical leak (say methyl bromide, for example) can cause problems, too.  There's a fourth category for all detection & measurement equipment, but I'll address that next posting.

But how often should you clean a top notch temperature gun (say our Top Temp Gun or the Flash Point Temp Gun)?  Here's the answer from our techs:

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If the following procedure is not followed, there will be an error of accuracy from 10 degrees F to 40 degrees F minimum for the readings.
  1]   EVERY unit we supply should be cleaned weekly to eliminate dust, girt and grime that will build up on the lens system.

        1a.  This can be done using a soft cloth or cotton swab with alcohol.
 
  2]  The advantage of the IR100_2 and the TN425 is the low temperature range of -76 to check accuracy of the unit.

       2a.  Simply fill a vessel with ice and water : check the temperature:  reading should be between  27F to 35 F.

       2b.  There should be only a drift from 32F .. 27 low and 35 high

       These readings should be within our stated accuracy.

   3] Finally, let's go beyond the lens issue...


        Sometimes dust and particulates from emergency response scenarios can be blown beyond the outer Fresnel  lens, and even  beyond the hard glass lens and right into the microprocessor.
         THIS event will cause an additional error in accuracy of 10 -20 degrees of the reading.

         There is NO WAY to take the unit apart and blow out the dust without destroying the guts of the unit.

 If the unit is too far out of whack as determined by ice water test...   then we will need to replace it ASAP.


Remember that high end infrared temperature guns are precision instruments.  Treat them like they are and they can help keep you and your team safe.

Monday, August 15, 2011

Looking Down the Barrel of an Infrared- Part One




You're looking at a Fresnel lens sysem that we use for our infrared temperature guns.  Notice the ridges along the tapering cone that lead down the barrel to the lens.

I've been hammering this theme home for a while as regards photoionization detectors, but I promised to bring it around to our infrared temperature guns and today I will,

Even though we handle 100:1 distance to spot infrared temperature guns with Class III laser sights, the situations that hazmat responders have to deal with can involve lots of smoke, dust, chemical leaks and or extinguishants.  If you're not using our Top Temp Gun, it means you'll have to be even closer.  With somebody else's infrared temp gun, say a 50:1 distance to spot ratio, you'll have to be twice as close to get a decent reading.

What is distance to spot ratio?  For a 100:1 infrared temperature gun, it means that at one hundred feet you will be measuring a circle with a 1 foot radius.  That's a tight spec.  It's a real instrument that can save lives.

But what if, during an emergency run, you use your temperature gun in a smokey environment, or while your using it, extinguisher fumes blow your way.  Or chemical fumes from a factory?

The answer is that you have to clean it, just like in the case of the PID.  Swab the ridges and the lens with isopropyl alcohol.  Most people forget to clean the ridges that lead up to the main lens.  That's a cricital mistake.  A bad mistake.  Those ridges aren't there for nothing.  They're part of the instrument's operative principle.  So clean them as often as you clean the lens.

Clean them after every emergency you take the infrared gun to.  That way you'll be sure to get more accurate readings.  How inaccurate can the readings be if the unit's lens package (including the ridges)isn't cleaned?

I'll fill you in on that next time.