Humidity sensor or temperature sensor or both? Please help!

[desmond1310]

Hi, my project is to make a dish dryer, and I have doubts about which sensors to use.
One of the modes i plan to program is an Auto mode. The auto mode should estimate the time needed for my dryer to use to complete its drying task successfully. The two important hardwares i plan to use in this dryer are:
1) fans
2) and most probably a heating element
i have read articles and patents of dish washers and drying water-damaged buildings; i am convinced that heat will help evaporate the water vapor more effectively, and here comes the problems:

a) if i use the humidity sensor, aside from my budget issue for now, i have read upon this:

"The most important of these problems is the fact that the humidity sensor is not simple and practical. Most of these devices respond very slowly and are not accurate in environments with high condensation. Therefore under the conditions present inside the dish washer, measurement of humidity is quite difficult and generally require costly solutions. Furthermore the measurements taken, give information about the humidity condition at the point where the sensor has made the measurement, instead of giving an average value." -quoted from A DISH-WASHER WHEREIN THE HUMIDITY CONTROL IS MADE BY A TEMPERATURE SENSOR.

it also suggested that a temperature sensor as a substitute for the humidity sensor, but here comes the other problem:

b) since i am planning to increase drying effectiveness, i plan to use a heating element. and i came across this:

"the temperature sensor (8) placed in the air discharge duct (7) used for removing air from the dishwasher tub during drying process, measures the changes in the air temperature. An increase in the temperature (because of objects start to heat the air due to their thermal inertia) is evaluated as an indication of the dryness of the contents of the dish washer. Therefore, the present invention eliminates the requirement to use a humidity sensor for dryness control and provides control method for the operation of the fan." -quoted from A DISH-WASHER WHEREIN THE HUMIDITY CONTROL IS MADE BY A TEMPERATURE SENSOR.

Note: this application didn't mention the usage of a heating element. so if i were to channel in warm air, won't the sensor be influence by this warm air, and halt immediately? Although the idea above sounds valid, but i believe i lack the knowledge of how drying really works to be confident that heating element won't be needed.

Or should I include both? :\ Please advice me thank you!

[shahrul]

Use many sensor, ofcourse better. More information you get, more reliable.

For humidity sensor, maybe the response is low. It takes time to detect the changes. (or maybe it's hard to change air humidity)
For temperature sensor, it's ok. By it's application to detect temperature, I think it's can stand for high temperature.

That's why this application hard to apply. Easier on dryer manually and off after while using timing.

[robosang]

i support shahrul, use both and combine those sensor information.

[desmond1310]

okay thank you!