EZT-570S User Manual
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A good starting point is to use the maximum deviation found for the upper set point and use three
times the deviation for the lower set point. This allows the air temperature to drop further in order to
increase the rate at which heat is pulled from the product in order to compensate for its internal heat
generation.
Process Control
Process control also operates in the same manner for live loads as dead loads. However, due to the
fact that the product is generating heat, process control is typically unstable and produces
undesirable results with fluctuations and oscillation in temperature control. It is recommended to use
deviation control mode for these applications.
5.5.1.4
Considerations When Applying Product Control
Product control is a powerful tool, and when used properly, can decrease test cycle times and provide
more accurate and thorough product testing to insure the quality of your product. However, it is
important to consider all of the factors that may affect the test results.
Product Sensor Placement
Whether the product is a live load or a dead load, sensor location will play an important part in the
test results. If the test method is correct, but you are not getting the desired results, try changing the
location of the sensor on the product or change the orientation of the product within the chamber.
This may provide the results you were expecting.
Humidity Control
Relative humidity is a measurement of the amount of moisture in air at a given temperature as a
percentage of the total water it could hold at that temperature. If your test requires both humidity and
temperature control, product control may have a detrimental effect on the chamber’s ability to control
humidity. Since the air temperature varies in order to maintain product temperature, humidity control
will be affected by the difference in air temperature required to get the product to temperature. The
magnitude of this affect will be dependent upon your test conditions. Under some conditions, product
control may have to be turned off in order to achieve the test results you require, or more extensive or
tighter product control set point adjustments may be required.
5.5.1.5
How do I Know when Product Control is Active
When product control is not active, the product set point will follow the temperature set point. As the
temperature set point is changed, the product set point will automatically change with it. If you
attempt to change the product set point, the set point entered will revert back to the temperature set
point.
When product control is active, the temperature set point will be controlled by the product loop. The
temperature set point typically varies readily as the product loop drives temperature. The product set
point will also take user entry and control the value entered via the numeric keypad. The
“temperature” set point is then entered on the product loop as the EZT-570S is now controlling
product temperature.
The “units” display on the Main and Overview screens will also display the text “DUT Active” instead
of the temperature units, i.e., C or F. This provides the user with direct status indication that product
control is active and the temperature loop is under product loop control.
Summary of Contents for EZT-570S
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