Compare the Exergen Microscanner D-series thermometer with conventional alternatives:
|
Temperature Measurement Factors |
D-series IR Thermometers |
"Point and Shoot" guns and probes, including laser aimed units |
contact probes, thermocouples, RTD's, thermistors |
| 1 Pre-set Emissivity errors? | no effect | very sensitive | no effect |
| 2 Emissivity shift errors? | no effect | very sensitive | no effect |
| 3 User adjustment errors? | no effect | very sensitive | no effect |
| 4 Background reflection errors? | no effect | very sensitive | no effect |
| 5 Contact errors? | no effect | no effect | very sensitive |
| 6 Friction heating errors? | no effect | no effect | very sensitive |
| 7 Heat sinking errors? | no effect | no effect | very sensitive |
| 8 Time based errors? | no effect | no effect | very sensitive |
 The D-Series
is an entirely different type of instrument than conventional temperature
measuring devices. Designed specifically for the highest possible accuracy,
it is the only infrared instrument which can be certified as to NIST-tracable
accuracy on real surfaces of unknown emissivity, while completely free
of contact errors and heat sinking errors of contact devices. |
 Pre-set
Emissivity errors. The true emissivity of a surface is known
only approximately. Conventional IR devices without Exergen's Automatic
Emissivity Compensation System can only display an approximate temperature
over their entire temperature range. The "accuracy" specifications given
by most manufacturers are only for a "black body" calibration and do not
hold outside laboratory conditions. Black body calibrations do not include
emissivity shifts, ambient change effects on the target, and other phenomena
that introduce significant errors.
Emissivity shift errors. Even if an IR "gun" is set to the correct emissivity to read a surface accurately at a particular temperature, it does not mean that the IR "gun" will read the same target correctly at other temperatures. Emissivity of virtually all surfaces changes with temperature. A common assumption for conventional IR thermometry is that emissivity is constant with changes in target surface temperature. Real materials do not have this characteristic. |
User Adjustment Errors. A setting of emissivity = 0.9 on
an IR "gun" from one manufacturer will not necessarily match that of another
IR "gun" manufacturer. There are no standards set in the industry on the
precise measurement and meaning of "emissivity".
Background Reflection Errors. Even if emissivity is constant (see #2), there are still errors induced by changing ambient temperatures. For example, with emissivity = 0.9, ambient reflections account for 10% of the signal that the IR "gun" will see. If ambient changes, the IR "gun" will display a different target temperature, even if the target remains at the same temperature. |
Contact Errors. Thermocouples, RTDs. thermistors, and other contact devices only measure their own temperature. They do not measure surface temperature. Published "Accuracy" specifications are for the probes only, not the surfaces they must measure. Users must guarantee that the probes are brought the same temperature as the surface. Can you guarantee that your probes are brought to the same temperature as the targets to be measured? Friction heating errors. For moving surfaces, a contact probe is prone to frictional heating. The size of the error is dependent on the roughness of the surface, the speed, the coating on the probe, and so on. It is impossible to control all the variables. |
 Heat
sinking errors. For most non-metals, heat sinking errors can
be quite large. The heat transfer rate of the metal leads required on "contact
probes" conducts heat faster than the target material can replace, resulting
in unknown and fairly large errors. In general, the less dense the target
material, the larger the heat sinking error with a contact probe.
Time based errors. Contact temperature probes are slow. The temperature of a target can change more quickly than most probes, resulting in errors in real time measurement. |