Specification :

Specifications
Backlit display for use in poorly lit areas
Fluke 61 Yes
Fluke 63 Yes
Fluke 66 Yes
Fluke 68 Yes
Holds temperature readings
Fluke 61 Yes
Fluke 63 Yes
Fluke 66 Yes
Fluke 68 Yes
Range
Fluke 61 -18 to 275 º C ( -0 to 525 º F)
Fluke 63 -32 to 545 º C ( -25 to 999 º F)
Fluke 66 -32 to 600 º C ( -25 to 1100 º F)
Fluke 68 -32 to 760 º C ( -25 to 1400 º F)
MIN/ MAX/ AVG
Fluke 61 N/ A
Fluke 63 MAX
Fluke 66 All
Fluke 68 All
Datalogging
Fluke 61 N/ A
Fluke 63 N/ A
Fluke 66 Yes
Fluke 68 Yes
Distance to spot ratio
Fluke 61 8: 1
Fluke 63 12: 1
Fluke 66 30: 1
Fluke 68 50: 1
Hi-Lo Alarm
Fluke 61 N/ A
Fluke 63 Yes
Fluke 66 Yes
Fluke 68 Yes
Optional RTD probe ( contact temperature measurement)
Fluke 61 N/ A
Fluke 63 N/ A
Fluke 66 Yes
Fluke 68 Yes
Emissivity
Fluke 61 Fixed at 0.95
Fluke 63 Fixed at 0.95
Fluke 66 Digitally adjustable ( from 0.1 to 1.0 by 0.01)
Fluke 68 Digitally adjustable ( from 0.1 to 1.0 by 0.01)

Measurement Accuracy
Fluke 61
-18 ° C ( 0 ° F) to -1 ° C ( 30 ° F) ± 3 ° C ( 5 ° F)
above -1 ° C ( 30 ° F) to 275 ° C ( 525 ° F) ± 2% of reading or 2 ° C ( 3.5 ° F)
( With the instrument stable between 23-25 ° C)
Fluke 63, 66, 68
-32 to -26 º C ( -25 to -15 º F) : ± 3 º C ( ± 5 º F)
-26 to -18 º C ( -15 to 0 º F) : ± 2.5 º C ( ± 4 º F)
-18 to 23 º C ( -0 to 73 º F) : ± 2 º C ( ± 3 º F)
For targets above 23 º C ( 73 º F) : ± 1% of reading or ± 1 º C ( ± 2 º F) , whichever is greater