Why measure oxygen partial pressure?
The oxygen partial pressure can be used to calculate the water vapor content, that is, the oven is working properly and calculate the current relative humidity in the box.
Relative humidity RH% = (WVP ÷ WVPmax) x 100% = {[BP-(ppO2÷0.2095)]÷ WVPmax} x 100%
in:
WVPmax is the saturated water vapor pressure at the current temperature , and you need to know the temperature value inside the steam oven.
WVP real-time water vapor pressure .
ppO2 Partial pressure of oxygen in the chamber.
BP is the air pressure inside the steam oven.
Why measure relative humidity?
Crust Color :
High humidity can cause baked goods to have a lighter crust. This is because excess humidity blocks heat from being transferred directly to the product. Additionally, condensation that forms on the surface of the dough acts as a natural insulator against heat transfer. In this case, the crust temperature during baking is lower than the target temperature, resulting in a lighter-colored finished product.
Dough expansion and product volume :
High humidity increases the volume of baked products. A moisture-rich baking chamber reduces the driving force for moisture migration. As a result, the product loses less moisture to the hot air, allowing the dough/batter to remain moist and expand/stretch further before the crust sets.
Moisture Content :
High humidity increases the moisture content of baked products, which can affect the shelf life and sliceability of the product.
Bread Crust Characteristics :
Some artisan breads and hearth breads require steaming to produce surface condensation and a shiny crust. The higher the humidity, the smoother and thicker the product's crust will be.
How to adjust relative humidity?
Purge system:
Oven humidity and heat distribution is usually controlled by fixed speed exhaust fans and/or dampers . They can be adjusted manually or by electric valves controlled by a PLC . In modern steam ovens, it is usually controlled by a variable speed exhaust fan.
Fresh air:
In some applications, for safety reasons, the hot and humid air can be replaced by fresh air during the baking cycle to improve product characteristics.
Steam Injection:
Monitor and adjust saturation level, pressure and amount of steam injected into steam ovens for baking hearths and artisan breads.
The following diagram shows the difference in humidity in the oven when the damper is open or closed:
Damper open:
Here, Shenzhen Xinshilian Technology Co., Ltd. recommends an oxygen detection sensor O2S-FR-T4.
This sensor is a small gas sensor developed by SST in the UK specifically for detecting oxygen partial pressure.
enter:
Operating: 4.35VDC ± 0.1VDC (1.85A)
Standby: 2VDC (0.85A)
Output (for use with one of the following boards):
O2I-Flex: Digital signal RS232, analog signal 4~20mA, 0~10Vd. Supports 3 signal outputs at the same time.
OXY-LC: Digital signal: RS485, analog signal: 4~20mA or 0~10Vdc. Only one signal can be selected from the three outputs.
wiring: