I don't sell any of these nor do I receive any remuneration if you buy them, and I have not personally reviewed all of them, they are listed here to give you perspective
Introduction
infrared thermometers allow you to ascertain the temperature of objects from a distance by measuring the infrared wavelength of light that they are emitting
this page only discusses those devices which just give a temperature readout rather than a visual heat map and temperature read out - for these see thermal imaging cameras
the temperature range will vary depending upon the device:
those designed for human foreheads will only go to 50degC in general even in “object” mode but are far more accurate than most industrial devices
human skin has an emissivity of 0.95-0.99 but these forehead thermometers use an emissivity of around 0.78 in human mode to give a reading that approximates oral temperatures
when set to object mode they presumably use an emissivity of 0.95
medium temperature “industrial” / BBQ models may have a temperature limit of around 500degC
high temperature industrial ones will have a wide range of temperature from minus 50degC to 1500degC
industrial ones usually have:
1 or 2 lasers to help aim the device
ability to set the emissivity from 0.1 to 1.0
a narrow “angle of view” which is measured as distance to spot (D:S) ratio
wider ones for general use are 16:1, more industrial very high temp usage are 30:1 allowing you to stand 3m away to measure a 10cm area
12:1 models are generally best at 36cm distances from objects
newer sensors have a faster response time of under 250msec, older ones are 500msec
more expensive ones will be drop proof to 3m and water-resistant
industrial IR thermometers are NOT good for assessing fevers as they are NOT sufficiently accurate, even the better ones have an accuracy of only ±1.8°C and that assumes you have ascertained the correct emissivity value!
in fact they are NOT very accurate for most of your needs of ambient temperature measurements where a +/- 2 degC error when measuring something at 20degC can give a measure anywhere from 18-22degC - probably NOT useful
where they are great is for measuring very hot temperatures and a few degrees out does not make any difference for most uses.
the device will need to have the emissivity set for the type of material you are measuring otherwise you will get inaccurate results
for many objects, their emissivity CHANGES significantly with major changes in temperature!
SOME devices have a FIXED emissivity of 0.95 which you cannot change limiting its versatility greatly!
they are however adequate for most non-reflective non-metal surfaces, and painted or non-reflective coated metals
eg. Klein IR1 as emissivity set to 0.95; HoldPeak HP-960C for cooking;
to ascertain the emissivity you can either:
use a table look up
for most materials, emissivity is the opposite of reflectivity
unoxidised aluminium = 0.02-0.03 depending on temp
oxidised aluminium = 0.11-0.19 depending on temp
polished stainless steel = 0.07
matte stainless steel / aluminium = 0.2-0.3
unoxidised cast iron = 0.21
gravel = 0.28
water = 0.67
moderately oxidised cast iron = 0.65-0.78 depending upon temp (strongly oxidised = 0.95)
heat a target object well above room temperature and measure it by a trusted contact probe and via IR making sure the IR is not detecting the probe itself (best to remove the probe)
ensure there are no hot objects nearby that could cause reflections that interfere with the measurement
The surroundings of the object should have the same temperature as the sensor ie. don't measure it inside an oven
Adjust the emissivity setting on the IR sensor until it measures the same temperature as the contact probe
measure it by painting part of it matte black:
paint part of it with matte black BBQ paint
heat the object as above, measure the painted area at emissivity 0.95 then adjust emissivity whilst measuring non-painted area to get the same temperature reading.
wide temperature range devices for really hot objects at a distance
HoldPeak HP-1800C
-50~1800℃ (-58~3272°F)
50:1 D:S thus designed for being around 5m or more from object
HP-1500APP version gives Bluetooth smartphone control $AU84
older model, HP-1420C has older sensor and measures to 1420degC
HoldPeak HP-985B
as for HoldPeak HP-1500C however:
-50℃～1360℃(-58℉～2480℉) accuracy ±3°C
16:1 D:S makes it more useful for cooking than a 30:1 model as you only need to be 1.6m for a 10cm spot not 3m away, 0.7m gives a 4cm spot, 2m gives a 13cm spot;