Humidity sensing for food processing

[3v0]

Micorwave ovens have cycles that run a while then stop heating and do some sensing. On mine it is popcorn and sensor reheat.

I would guess they are sensing humidity. If this is true how do the protect the humidity sensors ?

Has anyone salvaged such a sensor. What are they using ?
why

I am building a controller for a dehydrator. I could leverage a setup I built with a Honeywell HIH-4000-001 sensor that will give me both temp and humidity. I am worried about contamination. This from the datasheet sounds promising.

the RH sensor is a laser
trimmed, thermoset polymer capacitive sensing element with
on-chip integrated signal conditioning. The sensing element's
multilayer construction provides excellent resistance to most
application hazards such as wetting, dust, dirt, oils and
common environmental chemicals.

I would expect a microwave oven to be a harsher environment then the dehydrator. So I am wondering what they are using. Do they use any protection like a filter ?

 

[Reloadron]

Interesting question. I do think that the information regarding the sensor in quotes is more aimed at the protections afforded the sensor when used in what may be a harsh environment.

As to the microwave oven itself. Ours does use a few pulse modes but it has mainly to do with power settings. Meaning if I shove something in there and want some heat level other than High (my personal favorite) the power will pulse at different rates. Sort of like a PWM of the magnetron. I don't believe it senses humidity at all. Then too, I am sure these things vary as to their control. Also, it does have a temperature sensing probe so if you are inclined to shove a roast in the thing you can enter a center temperature for it to shut off at. Though I have never used the temperature probe I have reason to believe it is around here somewhere. Like I said, I only use one setting and that is high and enter a time. The wife used the more advanced features.

A friend of mine named Joe Kulis who goes by "Kastaway Kulis" has made a fortune by freeze drying (using dehydration machines) things like taxidermy and even bait for fishing. He also will taxidermy and freeze dry pets so Rover can adorn your house forever after his passing. Interesting enough he got several of his machines from a pharmaceutical company located locally called Bien Venue Labs. He does not do anything for human consumption that I am aware of but really interesting stuff.

Wish I could add more but I want to see how this goes for you and hope it goes well.

Ron

 

[3v0]

Mine has a cycle called sensor reheat. It is sensing something and without a probe.

It also has a popcorn cycle that pulses. I am thinking that when the popcorn pops it increases the humidity. When the humidity goes back down the popping is done and it stops.

EDIT: A quick google shows many hits for "microwave oven humidity sense". So they use humidity sensors. The question is which ones and do they protect them ?

 

[Reloadron]

Yeah, right on target, I found this:

The microwave system features the 6th Sense™ cooking system. A humidity sensor in the oven cavity detects moisture and humidity emitted from food as it heats. The sensor adjusts cooking times to various types and amounts of food. Sensor cooking takes the guesswork out of microwave cooking.

This led me to open the microwave oven and look around. It does have a popcorn setting I never noticed (I really need to expand my horizons) but nothing visible in the chamber itself. The thing does have airflow in and out of the chamber so maybe in my case the sensor is in the airflow somewhere. Interesting as when the popcorn pops or food cooks it gives up moisture, and once popped the moisture level drops.

Totally off topic but the wife noticed my sudden curiosity with the microwave, which led to a discussion of popcorn before the microwave was around in days of yore. Which led to TV Time and Jiffy Pop which led to This classic commercial. The bummer is I well remember that stuff.

Ron

 

[3v0]

Yeah sadly I remember it too. But we were too poor or too cheap (perspective) to use the expensive jiffy pop.

Now back to getting a body to inspect the sensor or tell us what they know about it.

 

[Reloadron]

Yeah, I doubt she would appreciate it if I begin to disassemble the microwave today. Then too, she is out of town next week. Someone here must have a handle on this stuff.

Ron

 

[cobra1]

The sensors used in microwaves are protected by Gold and/or Nickel, there is also another type used made of a ceramic that is pourus, the amount of moisture in the ceramic determines RH.

There is a sensor that honeywell make that has a built in screen, i belive it stops condensation on the sensor itself, the sensor has analogue output.