Topic: Wh32-ep with metal probe vs wh31-EP with plastic probe

[Ivan13]

Hello everyone, I take the liberty of opening this new discussion because I think it can be interesting for everyone.  A few days ago I had a wh32 box sensor modified into a wh32-ep, with a metal probe from the sensirion SHT35 instead of the plastic probe that is used by the ecowitt.

 Soon I will start the comparisons between the two probes using two identical sun screens, two standard meteosheild barani, positioned in the same location, in a swimming pool lawn.  The purpose is to understand the difference between the two types of probes.

 This is the link to follow the progress of the probe: https://www.ecowitt.net/home/index?id=24281

 P.s.  The probe sensor has already been aligned with the other sensors I have available

 At the moment I am comparing the metal probe sensor with a normal “box” sensor.

here are some photos. I created a sheet with drive in which I put the photos: https://drive.google.com/drive/folders/1-1wpo6Q4esIV4sKTmrtnG4mNm6PWBIRz

[Ivan13]

Here I have created another link with the drive in which I put the data collected yesterday and today is the related graphs in which you can understand the trend of the two sensors, that is, the sensor box and the metal probe. https://drive.google.com/drive/folders/1-4QUDFid06XDeSOvpCD8s9yorp8aMjYa

[ivano]

great ivan, if you rename the photos you created in the drive, it's even better;) for example "screen temperature of 08/10/2020" or deviations of the day ... etc etc 

[Ivan13]

These instead are today's charts.  It can be seen that the box sensor is less reactive than the probe, in one case I arrived at 1.4 ° C less than the probe. The day was more sunny

This is the link of the folder drive: https://drive.google.com/drive/folders/1-9-owursvIveuitUW_E6GtllbeP4tBc8

[Ivan13]

I also add here the graphs of yesterday and today.  the two days were practically the same, from this afternoon it was cloudy.  maximum deviation of -1.7 ° C and average of -0.3 ° C.  This is the link from yesterday: https://drive.google.com/drive/folders/1-BnVIPUDvwnDZ-KB6GWsfjwp4v0E4VPr

This from today: https://drive.google.com/drive/folders/1-CqoGlQC2SuXRAwLuUzZ8YBzMZzeBi5b

I also added the humidity graph because it is also interesting. 
The graphs are the same as those of the previous times, i.e.:
- graph with temperature of the two sensors and radiation,
- humidity graph of the two sensors,
- graph on the deviation between the two sensors,
- graph on wind and gusts
- summary screen

[Ivan13]

Today's data: in today's graph I also added the data from yesterday evening, from about 7:30 pm.  I also added the precipitation graph, to better understand the current weather situation.

Usual drive link: https://drive.google.com/drive/folders/1-MajCcO8m6IQSsG97NBjn_eSxG1G9_h-

[zoomx]

Looking at the graph data it seems that the sensor overestimate every time there was the sun

since the sensors are in the same radiation shield

It was strange since the probe is inside a metallic case so I though that maybe there was an influence by the UV rays. Since I have an UV led flashlight, a UV spectrometer and a similar sensor I made some experiments.

I have an SHT30 in a metallic case like the Ivan13's one
I got my UV LED flashlight anch cheched it with the spectrometer. It is an Ocean Optics USB2000+ that I used with the OceanART V1.01 software.
This is the LED spectrum

The peak is around 365nm, I have a common UV LED.

Then I connected the SHT30 to an Arduino board and used the IDE plotter and put the flashlight over the sensor tiny hole and I got this

As you can see the temperature increased dramatically and the humidity decreased accordingly. When I removed the light the temperature decreased more slowly and the umidity returned to the previous value. Temperature is in °C and since i plotted 4 data every seconds the time in the X axis must be divided by four to obtain seconds. Every 100 values are 25 seconds.
Then I use a white LED flashlight but nothing happened.

So I tested the plastic of the Ecowitt WH31 using the battery cover.
Without plastic the spectrum is the one above but when I put the plastic over the spectrometer hole I got this

The signal is near zero.
So I put the flashlight just over the spectrometer hole with the platic battery cover in the middle and I got this.

No UV light but there is a light with longer wavelenght, maybe due to fluorescence effect

Snow, an user of Meteonetwork forum, suggested me to use the flashlight with the WX31 so i put it just in front of one of the two small slits that are on the WH31 case and I got this.

Then I put the flashlight over the SHT30 metallic case and used agai Arduino and the IDE plotter getting this one.

The increase is small and the return to the previous temperarute take about one or two minutes

Then I checked how the plastic battery case reflected the UV light and I got this

So there is an UV reflection added to another light that is the same that is transmitted across the plastic.

It seems that the sensor is sensible to UV light but I am not sure if it is a photoelectric effect or there is a real temperature increase.

[Ivan13]

Great work "zoomx”.

[Ivan13]

Data and graphs today 16-10-2020.  Mostly sunny day. I take photos from the meteonetwork forum.

- Temperature and humidity
- deviation
- Humidity
- Wind and Gust
- summary

[Ivan13]

There was further evidence to understand the difference between the two sensors.  If you are interested, I am attaching the direct link to the meteonetwork forum, where there are all the details.

Here the link: https://forum.meteonetwork.it/stazioni-meteorologiche-ecowitt-fine-offset/169543-wh3x-ep-sonda-in-metallo-vs-wh3x-ep-sonda-in-plastica-3.html

[Ivan13]

Finally a little while ago (around 15:00) I mounted the plastic probe sensor in the barani screen.  All this after having carried out an alignment with the other sensors and resulted accurate without the need to give any offset to either the temperature or humidity.

The data of the two sensors can be consulted at the following link: Ecowitt Weather.

I am also attaching some photos of the probe installation on the screen:




P.s.  I removed the tape from the sensor with metal probe that I had put on for the other comparison, as can be seen from the photo.

 Ivan

[Ivan13]

These are today's graphs.  Max deviation of -0.7 ° C, with average deviation of -0.133 ° C compared to the metal probe.  NOT BAD.  What I expected.  The next test will be to compare the box sensor with the plastic probe sensor.

[Ivan13]

The tests still continue.  In the last few days I have in comparison a plastic probe sensor and a dismembered box sensor of all plastics.  These are the latest comparison results:
I'll briefly summarize the latest results:

-- COMPARISON OF PLASTIC PROBE - METAL PROBE: maximum deviation of -0.7 ° C and average of -0.13 ° C
   - drive folder link with the collected data of those comparisons:
 https://drive.google.com/drive/folders/10_P59nEMIfN5f6dx1nO2CXq9a8PhdD-Y

 -- COMPARISON OF PLASTIC PROBE - BOX: maximum deviation even of -1.1 ° C and average of about -0.20 ° C
   - link to the folder with the graphs of those comparisons:
 https://drive.google.com/drive/folders/10sOdam3DGou7jr2z2mWTL3ptWFJsabZ9

 -- COMPARISON OF PLASTIC PROBE - DISMEMBERED BOX (still in progress): maximum deviation of -1° C and average of -0.06 ° C (much, much better than the normal box.
   - link to drive folder: https://drive.google.com/drive/folders/110c0rrSBAy9p0xNVU-6RBaAXK19eU_lL

[hmderek]

Between some of the Italian terms, am I to understand that your experience now is that the plastic probe is doing better than the metal probe in the same shield?

I'm also considering getting a second Pro Shield and using an SHT35. Not the Ecowitt though, Want to play around with an Arduino setup along with an SHT35 probe.

[Ivan13]

Between some of the Italian terms, am I to understand that your experience now is that the plastic probe is doing better than the metal probe in the same shield?

I'm also considering getting a second Pro Shield and using an SHT35. Not the Ecowitt though, Want to play around with an Arduino setup along with an SHT35 probe.

The plastic probe comparing it with the metal one registers maximum temperatures lower than the metal one and almost identical minimum temperatures.  In my opinion the best is the metallic one, looking at the graph you should understand, sorry for the terms in Italian



In the first photo there are the temperature data of the metal probe (blue), plastic probe (orange) and solar radiation (yellow).  As you can see, they measure almost the same temperature, the plastic one registers the temperature a little lower.  In the second photo instead there is the deviation of the plastic probe (orange) with respect to the reference which is the metal probe (blue).  The horizontal line you see and the average of the deviation

[hmderek]

In my opinion the best is the metallic one, looking at the graph you should understand, sorry for the terms in Italian

OK, yes I see that the metal probe measures a little higher during day time. How does it follow that the metal probe is better? Do you mean to say that the plastic probe is missing some of the heating during day time, considering that the shields should create equal conditions? In other words, the metal probe is better at taking on ambient temperature?

My first intuition is to assume the plastic one is better, but you are of couse comparing sensors, not shields.

[Ivan13]

In my opinion the best is the metallic one, looking at the graph you should understand, sorry for the terms in Italian

OK, yes I see that the metal probe measures a little higher during day time. How does it follow that the metal probe is better? Do you mean to say that the plastic probe is missing some of the heating during day time, considering that the shields should create equal conditions? In other words, the metal probe is better at taking on ambient temperature?

My first intuition is to assume the plastic one is better, but you are of couse comparing sensors, not shields.

In my opinion yes, in equal conditions (inside the sun screen) the right temperature is the highest one, already it is the sun screen that does this work.  If you also look at the humidity graph, you notice that the metal probe sensor detects a higher humidity than the plastic one.


P.s. in the graph the metal probe is the blue one while the plastic one is the orange one

[hmderek]

Do you have a link to the metal probe you are using? There seem to be some slight variations.

[Ivan13]

Do you have a link to the metal probe you are using? There seem to be some slight variations.

This is the link: € 5,89  6％ Off | Sht20 sht11 Sht30 Sht31 Sht35 di Temperatura e Umidità Sonda Del Sensore Impermeabile Antipolvere di Alta Temperatura di Marca Nuovo e Originale
https://a.aliexpress.com/_m04WIrj

you have to choose the SHT35 metal probe

Let me know if the link works.  if you give me an e-mail address I can send you a screen, here on the forum it doesn't do it

[hmderek]

This is the link

Thanks!