Billets Measurement With A150 Pyrometer
The AST A5 pyrometer works on the multi-wave principle with an automatic emission compensation.
Emissions according to:
– Surface hue (light after polishing, dark after graphite spraying).
-Surface texture – As a derivative of the technology process of casting logs (typically for the same alloy variations of emissions, the range may be 0.4-0.8).
For such variations, the experimental error of AST A5 pyrometer for billet measurements:
-Accuracy – fine-tuning at home (adjustment of the Dy Analytic parameter once, according to the Thermocouple reference).
-Mean error ± 0Cº with a standard deviation of 3Cº.
-In 3 measurements out of 1000, an error of ± 9Cº.
-In 50 measurements out of 1000, an error between ± 6-9Cº.
-95% of the measurement, will be between ± 0-6Cº.
The A150 pyrometer, is a single-wavelength instrument designed to work with objects whose emission capacity is constant.
Once you define the value, “ε” it only provides reasonable accuracy of the measurements If “ε ” remains as you set it.
In the case of aluminum billets in the extrusion process, the accuracy sample to be obtained using the A150, shall be as follows:
∨ Measurement accuracy of an aluminum Billet with one wavelength pyrometer compared to measurement with a thermocouple (TR)
∨ Billet average practice temperature TR (Temperature Real) = is 450˚C.
∨ To demonstrate the problematic nature of the measurement, we will perform some temperature measurements on different billets and thus find the average emissivity; let us assume for the demonstration that the found average emissivity is: ε = 0.6 (which is our fixed definition).
∨ This means that when the billet emission is ε = 0.6, the pyrometer
∨ Reading at TR = 450˚C, will be PT (Pyrometer Temperature) = 450˚C, error Δ = 0˚C.
∨ When for the same temperature billet TR = 450˚C, but the emission will be ε = 0.8, PT (Pyrometer Temperature) = 418˚C and error Δ = – 32˚C.
∨ When for the same temperature billet TR = 450˚C, but the emissionwill be ε= 0.4, PT (Pyrometer Temperature) = 475˚C and error Δ = + 25˚C.
For the above reasons, we never recommend our customers use a single-wavelength pyrometer for aluminum extrusion processes (billets and profiles).
Such temperature error range makes the use of such pyrometers a waste of money and time. you can not use in any way for process control or any other helpful task.