Humidity Sensors

[CharlieWayne]

I have several humidity sensors (mechanical & electronic). Most are cheap other then my venstar Tstat but all differ in their readouts and accuracy. This has me wondering which ones are right or wrong. Reading up about this is there are so many environmental variables that make calibrating these sensors difficult.

My question is what us everyone's experience with with humidity sensors that can be incorporated into HS such as 1 wire sensors? ( non weather station humidity sensors)

I'm not looking for tenths of a percent but would expect both stable readings and within a couple percent + or -

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[Olbrit]

I have 6 Everspring ST814s that, according to the website, are +-15% RH, so that certainly wouldn't fit into your +-2% requirement.

However, I got these more useable by buying a separate non-Z-Wave NIST calibrated temp/humid sensor and sitting all 7 sensors side by side on a table for a few days and noted their readings every few hours or so. Using the NIST sensor as the datum I could then determine an approximate deviation for each ST814 and include that in any HS calculations/views. (It's by no means a linear deviation and so this is a rough technique that probably brought the margin of error to around +- 3%, but that's good enough for me as I only need a reasonable sense of the internal/external humidities).

I'll be interested to read about more accurate solutions that others suggest.

[Rupp]

The one-wire sensors are advertized at +-2%.
http://www.hobby-boards.com/store/pr.../Humidity.html

There is at least one one-wire plugin that would work to integrate these into HomeSeer.

[Pete]

Here I have been using 4 types of 1-wire combo temperature and humidity sensors.

1 - AAG very old combo sensors - first gen - tiny circular combo sensor about 1/2 the size of my thumbnail - parasitic - after around 15 years still working just fine.
2 - newer AAG combo sensors - in the legacy telephone jack cases - don't recall when I purchased these - still working fine - did purchase these from AAG.
3 - Hobby boards combo sensors
4 - Midon Design combo sensors

Most recently I like the Midon combo sensors. Today currently utilize 3 Midon Design Temp0X 1-wire devices and 3 Maxim Integrated Serial 9097's and 1 noname USB 9097 with two mini stereo jacks on it for the 1-wire sensors. Note that the Hobby boards and Midon Design combo sensors utilize different DC voltages. My preferences would be that all of the sensors be parasitic. They used to be but no longer are.

The last one above I purchased as a package with two sealed temperature sensors and cable and extension cables. It works as well as the Maxim Integrates ones which I purchased from Maxim.

Long time ago went to wiring in a star topology using cat5e with one run per sensor. Today's recommendations are a star / hub and spoke with sensors connected to one run in a perpendicular fashion. I have numerous temperature and combo sensors outside and inside of the house.

[CharlieWayne]

Re: Humidity Sensors

I got these more useable by buying a separate non-Z-Wave NIST calibrated temp/humid sensor and sitting all 7 sensors side by side on a table for a few days and noted their readings every few hours or so. Using the NIST sensor as the datum I could then determine an approximate deviation for each ST814 and include that in any HS calculation.

This is exactly what I'm getting at. Being many devices calibrated or not are all reading different specs, how.do you know which one is correct to establish a baseline?


On a diff note, environment can also impact accuracy either knowingly or not. What has started this whole concern of mine is the data records I'm getting from a Tstat with.humidity sensor. I started seeing large rises in humidity during times it should be falling. I bought 2 other devices as I first thought a defective humidity sensor in my Venstar T1900 Tstat. After comparing each temp/humidity combo device I notified little diff in temp but humidity was not consistent.

What I suspect the issue with my incorrect Tstat reading are that the blower motor is sucking Hot Humid through holes in my walls top plate, down the wall and through the vents on the actuall Tstat. The issue with data is that once the A/C kicks on then the humifty readings slowly rise very high, and then when u turn the HVAC off the humidity drops 10-15% in 90 seconds or less. My point here is that environment plays huge factors into accuracy and if these swings in humidity were no so severe, I would have likely never found out about this error.

Pete I think has a lot of experiences with many systems as well Rupp from the post I read. What have you encountered with errors and how did u detect or correct such?



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[Pete]

I don't really see too many differences in temps and humidity except for rooms that are not utilized and where the vents are closed. I do also have a few HAI temp and combo temp / humidity sensors.

The HAI Omnistat2 also has direct connects to more sensors such that you can utilize an averaging between these sensors for setting your thermostat. I purchased a few of those a couple of years ago to play with.

I have left the control and scheduling of the HVAC to the HAI panel and thermostat and HAI panel and thermostat/panel connected sensors. I utilize the 1-wire sensors for my own thing and comparing the temperatures to the HAI temps which are relatively the same anyways. I do utilize the 1-wire humidity sensors in the basement and it is kind of indirectly connected to the de humidifier.

I do keep my furnace fan on 24/7. It's been very warm here in the last few days and I have kept the thermostat at 72 (hold). In the basement though I do run a dehumifier. Looking just now noticed my wife set it to 70F instead. House temps are about 1-2 degrees higher on the second floor.

I did though replace the outside AC unit last year. Old one was some 10 years old which kind of PO'd me. That said installer "was" the partner / owner of an HVAC company. He is semi retired and his partner is totally retired. I have known him and his partner (she is also retired) for some 25 years now. I did help / watch the installation and put the endeavor in his hands. The unit outside appears to be twice the size of the old unit but has a similiarly sized compressor. It's been working fine but I hear the rise and fall of the line pressure which bugs me a bit and I have called him regarding said concern.

Over the years though as I changed over to utilizing the Omnistat RC-80 and automating the whole HVAC thing it did cause some grief in general. Old fashioned methodologies versus what I was doing "complicating" things.....meanwhile learned much diagnostics and DIY stuff relating to my HVAC setup ....that and concurrently doing IT stuff hanging around their offices for some 25 years or so....

[Steve Q]

Humidity Sensors

Charlie, how do you use the humidity data with Homeseer? Do you have events that are triggered by humidity? I have only one digital humidity sensor and it is not hooked up to HomeSeer. (It is a wireless Meade Instruments sender, but I do not have the receiver). I have moved it all around the house for the past year and it has not provided any information that I didn't already know. In the summer, high humidity is a problem. My air conditioning is my only source of humidity control. But the humidity is was it is. I would not use Homeseer to run the AC more to lower the humidity. In the winter, low inside humidity is the issue. I have a humidifier on my furnace controlled by a humidistat. The humidifier works when the furnace fan runs. In the winter, Homeseer turns on the furnace fan (via my Z wave tsat) multiple times throughout the day to even out the temperature and add humidity. This approach works well. I suppose in the winter I could monitor the humidity and run the furnace fan more or less based on the humidity setting, but this approach runs counter to my energy conservation approach!

Steve Q


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[Pete]

Yup here in the winter I do control the humidifier and try to get some 35-40% even humidity levels throughout the house.

Now with the heat humidity levels are running some 45-50% in the house except for the basement which I keep at lower levels.

Homeseer does the double checking of my temps and humidity levels more than anything with a "look see" but do not touch methodology thing.

[Olbrit]

This is exactly what I'm getting at. Being many devices calibrated or not are all reading different specs, how.do you know which one is correct to establish a baseline?

You're right, initially you can't know if any of them can be used to establish a baseline, which is why I invested in a 3rd party calibrated temp/humid sensor from this company: http://www.control3.com/cgi-local/fu...?col1=Humidity. This removed my guesswork and if I feel like it I can send it back for recalibration every couple of years or so.

I use Jon00's excellent graphing utility to which he kindly added an 'offset' capability for me, so I can enter the average deviation from datum for each temperature and humidity reading, which means that the graphs below show the 'corrected' data.

[CharlieWayne]

Olbrit: do u have a conditioned attic with foam on the underside of the roof deck?
I'll assume those numbers in you attachment are from your FL home?
That's good idea on buying a certified humidstat to set your base line.

[CharlieWayne]

Re: Humidity Sensors

Charlie, how do you use the humidity data with Homeseer? Do you have events that are triggered by humidity? I have only one digital humidity sensor and it is not hooked up to HomeSeer. (It is a wireless Meade Instruments sender, but I do not have the receiver). I have moved it all around the house for the past year and it has not provided any information that I didn't already know. In the summer, high humidity is a problem. My air conditioning is my only source of humidity control. But the humidity is was it is. I would not use Homeseer to run the AC more to lower the humidity. In the winter, low inside humidity is the issue. I have a humidifier on my furnace controlled by a humidistat. The humidifier works when the furnace fan runs. In the winter, Homeseer turns on the furnace fan (via my Z wave tsat) multiple times throughout the day to even out the temperature and add humidity. This approach works well. I suppose in the winter I could monitor the humidity and run the furnace fan more or less based on the humidity setting, but this approach runs counter to my energy conservation approach!

Steve Q


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Hey Steve, right now I only have my Venstar Tstat hooked up to HS and am using McsTemp to build a data base. Today triggers are not the intent but once I expand the system, I will start to incorporate some triggers such as bathroom humidty for exhaust fans, humidity triggers for a whole house dehumidifier, warnings through email or HS speaker client for extreme humidity (cautious about mold or fungus), and anything else that might come up.

Right now my main imtemt is to you all this as a diagnostic tool. One of the additional humidity sensors I have is a Meade temp/humidity station with remote sensors as well. It works and I make note of it to watch my attic temp and humidity but it has its limits.

In the above picture I attached the data is overlaid on each other. By looking at multiple sources of data I can use this to troubleshoot. Let me show u an example.

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[CharlieWayne]

Re: Humidity Sensors

Sorry, I didn't finish my post.

So as an example in above attachment,
Green is Cool Setpoint
Purple is Actual Temp
Blue is Actual Humidity.
Tstat has a 3 degree deadband.

At the 2nd 8am-9am the actual temp hits the top of the deadband Turing on the A/C system. U will see the humidity start to rise almost 10-12% when in fact running the A/C should dehumidify.

At around 2pm my A/C shuts off and then the actual humidity drops about 18% in mins.

If I had humidity sensors that would.feed this data base, I would likely find that attic humidity levels would resemble the peak levels of humidity on the chart.

Now based on this observation using the overlaid charts, I believe that when my Air Handler turns on it is creating a vacuum in the house and drawing attic are down through the wire holes in the walls top plate and then through the hole in the wall where Tstat is mounted.

A little bit of caulk, foam, or acoustical sealant on the top plate would confirm my suspicions.

Now this is just one of many examples of how it could be used.

Steve, you said in the summer you have very high humidity levels yet in the winter you have to run a humidifier a lot. Setting up sensors inside the building envelope, attic, and outside might start showing you where your faults are. Correcting these faults would have major impacts on both energy and comfort. A simple blower door test might door the same but where's the fun in that.

In the coming time I plan to start a simple 1 wire network to gain better understanding of my home and the retro needs to.conform with today's energy efficient models.

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[Olbrit]

Olbrit: do u have a conditioned attic with foam on the underside of the roof deck?
I'll assume those numbers in you attachment are from your FL home?
That's good idea on buying a certified humidstat to set your base line.

Hi Charlie, well spotted! When I bought the FL house in 2009 I found the HVAC ran 8+ hours/day in Summer, barely kept up with the setpoint and cost a fortune in electricity. The HVAC fan coil and ducts are in the attic that could reach 120+ degrees when it was 90 outside, plus 1/3 of the roof was flat i.e. no attic access. Roof underside icynene foam wasn't able to be applied, so after research I bought SureCoat and painted the entire outside roof area, shingles, flat asphalt, etc., plus I had lots of blown insulation applied in the attic space, and installed a solar-powered attic fan. Result was an attic that rarely goes 5 degrees above outside ambient temperature, but does not have to be conditioned. Made a huge reduction on the frequency and duration of HVAC runs and saved me a ton on electricity costs.

[NeverDie]

Being many devices calibrated or not are all reading different specs, how.do you know which one is correct to establish a baseline?

You can run a saturated salt test. The 75% relative humidity saturated salt test can be made using regular table salt:

http://harizanov.com/2013/06/dht22-a...y-test-part-1/

http://harizanov.com/2013/06/dht22-a...-test-part-22/

Also, Ambient Weather sells a couple different tests that operate on a similar principle. With their gear, you seal your sensor/device in their ziplock bag that will attain a standardized RH.

[Pete]

A bit overpriced just purchased a 1-wire temperature sensor with a power LED on it. I've never seen one of these before and its more of a curiousity purchase. I could make a little glowing glass jar outdoor sealed temperature sensor out of it....

Ebay search: Digital DS18B20 Temperature Measurement Sensor Module

Price: $4.39

Specs:
1. board DS18B20 chip left 3P hole seat easily accessible DS18B20 chip.
2. pin chip has all the leads, built-in pull-up resistor.
3. Onboard power indicator.
4. board size: 21 (mm) x10 (mm)