interference on a HIH-5030 humidity sensor

[cobra1]

Hi,

Im having a small problem with a humidity sensor, HIH-5030.

Iv got it all working fine and displaying the correct results, except when i touch it.

When i touch the sensor, the reading shoots up, when i stop touching it, it drops back down quickly (lower than the actual humidity) and then slowly climbs back upto the right reading.

Now i know the obvious answer is dont touch it, but it happens even if i put my hand within a few inches of the sensor.

Iv read that these sensors are based on capacitance, is this why I affect it???
if it is is there any way to stop it or limit it?

An example is if its on 40% i touch it and it goes upto the 90s
I really could do with finding this out as this sensor has to go into an animal enclosure and i think the animal is going to cause the same problem with the sensor.

 

[Roff]

It would help if you could provide a photo of your test setup.
Your sensor's internal amplifier could be oscillating, or, if you have it connected to an external amplifier, that could be oscillating. Have you bypassed the power pins with a capacitor, such as a 100nF ceramic cap?
If you determine that it is not oscillating, can you put the circuit in a Faraday cage? This can be simply a small metal box, made either of solid metal (aluminum is commonly used), with small holes for air circulation, or an enclosure made of wire mesh. This will shield the sensor from the effect of the approach of your hand, an animal, or whatever.

 

[Vizier87]

From my experience with humidity sensors, the sensor DOES respond to the human touch. Humans or animals also give out moisture, so it should react accordingly.

Anyway, like Roff said, you need a Faraday cage. Or for me just an enclosure to make sure it doesn't get on oily hands.

 

[cobra1]

Hi guys, thanks for your replies

another member on here has this same sensor and his does the same thing, i am told this is normal, so i guess i will just plod on.

 

[Roff]

Hi guys, thanks for your replies

another member on here has this same sensor and his does the same thing, i am told this is normal, so i guess i will just plod on.

You don't have to live with it if you think it's going to be a problem. Just put in in a small aluminum box that has a few small holes.

 

[Vizier87]

yeah, anyway humidity sensors are pretty fragile. Mine's with a thin glass encapsulation around the capacitive material, it looks pretty vulnerable if something falls on it.

 

[Reloadron]

CAUTION
IMPROPER HANDLING
• Do not remove the sensor from its original protective
packaging until it is ready to be installed.
• Do not touch the sensor surface. Use latex finger cots.
Handle the sensor by its package edges or leads.
• Do not allow objects to enter the cavity of the sensor
element.
Failure to comply with these instructions may result in
product damage.

Once installed and during install these sensors should not be touched. When installed these sensors are in a protective screen and not just left open and exposed. There is also this:

• The sensor’s housing does not provide electrical safety
isolation. Mount the sensor in a location where it cannot
be touched, or where a surrounding barrier prevents
human contact.

They seem pretty to the point about mounting and touching. The above quotes were taken in part from the data sheet.


Ron