Answer: Oven temperature uniformity is important to ensure uniform heating of the product. This is different from control sensitivity.
Uniformity – is the greatest deviation, in degrees, between the lowest and highest temperature points within the work area. For example, it is important to note that ±5°F represents an actual difference of 10°F (5.5°C) between the highest/lowest measured points in the oven/furnace.
Control Sensitivity – relates to the ability of a control instrument to measure and react to temperature fluctuations at a given set point.
Many factors influence uniformity:
- Controller calibration
- Sensor calibration
- Sensor placement within the work area
- Oven operating temperature (higher temperature/greater variables)
- Air circulation (the greater the air circulation, the better the uniformity)
- Placement of the product within the work area
- Product geometry
- Airflow pattern
- Heat loss through walls
- Metal-to-metal conduction
It is important to take all of these variables into consideration and to utilize a 9-point thermocouple test to ensure that the specified uniformity is obtained for the application. Although this 9-point test is not always included with the oven purchase, it is recommended and usually available for an additional cost. Some applications such as paint or resin curing require a temperature uniformity of ±10°F (±5.5°C). Many drying or preheating processes only require a uniformity of ±20°F (±11°C). Some technical processes need a uniformity of ±5°F (±2.7°C). Knowing your temperature uniformity requirements will help with oven selection.