The new response to temperature control in ovens.
Both the accuracy and uniformity that is currently expected by a laboratory oven reconsidered a deeper investigation about how to improve the aspects of stability (or accuracy) and uniformity, that's the way that BLAST SYSTEM was born.
BLAST SYSTEM is exclusively designed for Ovens, by getting optimum performance based on the formula which takes as reference data the rise and fall of temperature to a greater extent than any other PID controller.GROUNDS
The accuracy and uniformity that is currently expected by a laboratory oven both reconsidered a deeper investigation about how to improve the aspects of stability (or accuracy) and uniformity.
Although, there is a high percentage of probability to get stability and uniformity by means of a forced circulation of triple chamber, where the air enters at temperature of operation within the working chamber (without numbers in the percentages, since there are many variables that influence to a greater or lesser degree). The real forced circulation with the preheating chamber means a high cost, which can triple the value of a natural convection oven. Even though, in the cultivation ovens that work at low temperatures, forced circulation is not justified, since the improvement in temperature uniformity is inconsiderable.
Trying to return to the issue of thermal management, we began again to rethink the temperature controller. Generally, a control is sought in the market that can provide the necessary accuracy services according to the quality of the oven.
Regarding the manufacturers of controls, the company can carry on better controls every day, but always bearing in mind that they must be for all types of use: oven, thermostatic baths, bakery's ovens, fridges, etc.
With the consequent idea of being for all products independently of the operation, this type of controls turn to be quite expensive if they are relatively good and with many functions to be able to be implemented in a wide range of products
Until the arrival of BLAST SYSTEM the manufacturers of ovens had to choose a quality and accuracy control and it involved the implementation of these high-cost controls and, in general, they were difficult to use and / or easy to deprogram, they were very complete, but with many performances that are not for the use of an oven.
Therefore, for the exclusive use in ovens, it was necessary a control that would provide:
- Maximum accuracy
- Good uniformity
- Easy use
- Moderate cost or cost matching the benefits.
The development of the BLAST System involved the approach of research with electronic and physical engineers and also an enquiry to national and international electric power companies, avionics metrology engineers, and also companies devoted to calibration seeking accuracy as a subject of study, which offer calibration training.
At the beginning of the project, it was observed that there were temperature measurement equipment with an accuracy of 0.000005 ºC approximately. The idea was to develop a practice as economically as possible for unnecessary functions and invest as much as possible in parts and materials of the highest quality to get the best accuracy.
As far as the control itself it is logically linked to a temperature measurement that must be extremely accurate.
It would be useless for the control to be accompanied by an inadequate sensor. The sensor used must be a PT100 that has a platinum wire that increases the electrical resistance with temperature, in a non-linear way.
"The most common thing is to see 2-thread sensors, but 3-thread sensors should be used to avoid the error that occurs with the length of the cable from the control to the steel sheath that checks the temperature.
These three cables have the same electrical resistance, since the measurement system is based on the "Wheatstone bridge".
Although there are 4-thread sensors that can be more accurate than 3-wire sensors, they work in the following way:
a known current goes through 2 of the wires and it causes a potential difference, the other two cables are connected to a high impedance voltmeter. The reader is considerably more expensive, even though the main problem is that the rises or falls of current voltage are much more affected than the 3-thread sometimes with bigger errors, if instead of a voltage of 220V there is 190V or 240V. The 3-thread PT100 option is the ideal one in practice, being Class A for the best accuracy.
The control takes into account in its design the Joule effect (P = I * I * R) correcting that error that takes place generally at low temperatures.
The control has the lowest possible electrical excitation, the lowest in itself achieved by a control, getting an important decrease in the error that occurs with the power of self-heating and a decrease in the error that entails the temperature checked by air the temperature is taken by air (it is more accurate the temperature check of a liquid medium).
The Fuzzy Logic PID control is used from an oven to a washing machine, which must be adapted as much as possible for each product where it is used.
The BLAST System PID controller achieves greater accuracy and uniformity of temperature in the internal chamber throughout the range offered by the Controller. BLAST SYSTEM
The BLAST System PID control is a new and exclusive temperature control system that is based on an individual mathematical calculation for each oven model of the PID parameters (Proportional, Integral and Derivative) in the Auto tuning, it optimizes the variables and avoids the permanent recalculation of the BLAST System in the same way as it is in the Control Fuzzy Logic. REAL PERFORMANCE OF TEMPERATURE IN WORK PROCESS
The BLAST System was exclusively designed for ovens and it is for this reason why aspects related to it have also been taken into account for an optimum development such as:
• The weight and volume of the products that are placed inside
• Useful camera size
• Location of the heat source (resistances)
• Power of resistances
• Inertia of the resistances
• Position of the temperature sensor
• Camera construction material.
• Work temperature
• Position of the temperature sensor
• Top aerator and its way of dissipating heat
• Radiation indexes of internal material
• The doors and their sealing.
All these variables make up a complex mathematical formula, which must work at any temperature offered in the range of the Control and that large number of variables make it instead of a temperature control, it is a temperature system, hence the name System BLAST .
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Exhibitor Data Sheet