Hi Samantha,

actually, we have implemented something similar at the TECHNOSEUM this 
year. We are monitoring temperature and humidity with self-built loggers 
on the basis of the ESP8266, a microcontroller board that has WiFi. The 
loggers send their data to a website where it is stored and displayed 
for conservation and collections staff to monitor. Warnings are sent via 
email if certain threshold values are passed or there is a sudden change 
in a given time. At the moment 7 loggers are doing their duty on and off 
site with additional loggers being added in the next months as we passed 
our second testing phase. It must be said that prior to this 
implementation I ran several tests (accuracy, 1-year-stability, extreme 
climate conditions) privately as a hobby before I was convinced enough 
to suggest the solution to my boss (our professional ones are old and 
became unreliable some time ago).

Along with the things William already suggested, here are some 
additional considerations:

- ALL sensors lose accuracy over time. The ones you buy have to be sent 
in for calibration, the self-built ones you can - but have to - test 
yourself. We use an Assmann psychrometer and in addition two of the 
three salt solutions recommended here: 
http://www.connectingtocollections.org/wp-content/uploads/2012/03/Calibration-using-saturated-salt-solutions.pdf 


- The checking interval is 6 months. The data sheet of these sensors 
give +/- 2% for relative humidity but we found them differing wider in 
testing. Something that can be corrected in the code, but also HAS to be 
corrected in the code.

- There is some coding to do, but if you have the IT guys on your side, 
this isn't much of a problem. For an IT guy the involved coding is a 
kindergarten game. Hey, I learned it and I have just a museum studies 
degree.

- As the ESP8266 needs power to send the WiFi signal, so ours need a 
power connection. We are experimenting with power bars, though. Will be 
the same with the raspberry, I guess.

- The system depends on available WiFi, obviously. We have some of our 
old thermohygrographs as a backup in places where we want to make sure 
we have continuous data, although so far there were no larger drop-outs.

The cost is at about 40 Euro a logger, including casing and power 
adapter, the exchange of a sensor is at about 8 Euro for the 
DHT22/AM2302, about 10 Euro for an ESP8266 board.

I tried to attach screenshots, but the list won't let me. Feel free to 
drop me a line at [log in to unmask]

Good luck with your project, please keep me posted because I'm 
interested how it works with a raspberry.


Best wishes
Angela

Angela Kipp
Collection Manager
TECHNOSEUM, Mannheim, Germany
http://www.technoseum.de

Join the Registrar Trek at http://world.museumsprojekte.de/
Follow us on Twitter @RegistrarTrek

This is a personal opinion, my institution can't be held responsible for 
anything I write.


Am 11.04.2017 um 16:59 schrieb William Shepherd:
>
> Hello Samantha,
>
>                 Most of my experience is with HOBO units as well but 
> ultimately if the units that IT has designed are accurate and can plot 
> the information in some way for you, why not? As great as HOBO units 
> are they’re not cheap and I’m guessing the Raspberry Pi units will 
> come in considerably cheaper. If IT here had laid the groundwork with 
> hardware and software I’d certainly trial it. Are you able to borrow 
> HOBO or similar units from a state organisation to compare readings 
> over a few months?
>
> Some things I’d ask IT:
>
> ·How accurate are the devices (+/-)?
>
> ·How is the data retrieved from the devices?
>
> ·How is the data plotted/read out?
>
> ·Are you able to retrieve and plot the data yourself?
>
> ·What is the cost per device?
>
> I’d be interested in hearing your experience going ahead as an option 
> for my institution as well.
>
> William Shepherd
>
> Collections Officer
>
> Swift Current Museum
>
> 44 Robert Street West
>
> Swift Current, Saskatchewan
>
> S9H 4M9
>
> Phone: 306-778-4815
>
> Fax: 306-778-4818
>
> *From:*Museum discussion list [mailto:[log in to unmask]] 
> *On Behalf Of *Samantha Sauer
> *Sent:* Tuesday, April 11, 2017 6:50 AM
> *To:* [log in to unmask]
> *Subject:* [MUSEUM-L] Raspberry Pi for a data logger?
>
> Good morning!
>
> I'm exploring ways to help track our temp/humidity settings on campus 
> in our archive, reading room, and museum. (I have the NPS 
> Conserv-O-Gram issue on data loggers by my side as I type...)
>
> It turns out that our IT team on campus is also doing something 
> similar utilizing raspberry pi devices to help track temp in computer 
> server rooms. It sounds like there is interest in collaboration to 
> help with the archive/museum needs, and I may be able to piggyback on 
> with a small investment for supplies. The raspberry pi would be able 
> to record temp/humidity readings and send via email.
>
> Has anyone else utilized these devices as a platform to track and 
> record data? I'm intrigued and tempted to try it, if only as a short 
> term experiment, since this is already happening in some form on our 
> small campus. It also seems like a neat way to incorporate a different 
> technology to read data. I am most familiar with HOBO data loggers, 
> but have not used raspberry pi devices in this way.
>
> Any insight and/or advice is welcome.
>
> Many thanks - as always!
>
> *Samantha *
>
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