Although your infrared thermometer meets the calibration test, keep in mind that the calibration test/procedure is in a controlled environment - ie: pointing the IR thermometer at a blackbody ( known source ), at a specific distance by a trained instrumentation person. Field of View or Distance Ratio is ONE important component of accurate IR measurement. Think of the IR Thermometer as a Pen Light. If you hold the pen light over your desk about 2" away you will see the light image of a 1/4" circle . When you move the pen light further away the circle gets bigger. 12" inches away the light image is now much bigger in diameter. Now you're viewing/measuring a much bigger area of the blood bag.. The IR Thermometer mentioned earlier by sgoertzen has an 8 to 1 ratio. 8" away from the blood unit has a measuring area of 1" circle/diameter. Movie it closer 4" and you're measuring 1/2" diameter and 2" away you're measuring a 1/4" diameter. If the operator is measuring the unit of blood 24" away the measuring area is now 3" diameter. The laser beam is just a pointing device. The warmest temperature of the unit of blood will be on the outside surface and measuring the blood temperature through a plastic bag will introduce an error if the emissivity is fixed at .95. I checked with an expert who said IR thermometers would need to be set to .85 emissivity to allow for the clear plastic bag. I agree with a previous post that stated the use of an IR Thermometer should be used as a screen ( Go / No Go ) and if out of range use a NIST certified surface thermometer held on the bag for about 8-10 seconds.
