Topic: Sensor with SHT35.

[krojan]

Two days ago in one of the WH31A sensors I replaced the sensor from SHT30 to SHT35. Everything works fine.

[galfert]

WHAT ??? !!!   

You did an SMD soldering! Impressive! Did you have anything covering the sensor hole while soldering to keep fumes away from damaging sensor?

Too bad that the firmware is limited to 10% - 99% RH and it still wont ever read 100% RH or below 10% RH.
I think all you gained was a little more precision in the 90% to 99% RH range.

I thought about doing this but I didn't see much to gain because of firmware. Besides I've never attempted SMD soldering as I just have a regular Weller WSD81.

[krojan]

Yes, I did SMD soldering.
I have a Chinese hot air station with fume extraction.
Earlier I trained a lot on other elements. I think it worked.
I now have a sensor better than Davis. It is a pity that the software limits the operation of SHT35.

[krojan]

I thought about doing this but I didn't see much to gain because of firmware.

Accuracy should also change in other temperature and humidity ranges.
See the entries in the attachments.

[WA4OPQ]

You could start a small business doing this.
I would be interested.

[krojan]

You could start a small business doing this.
I would be interested.

The cost of shipping to Poland and back makes this business unprofitable.
They should be able to replace the sensor at the local electronics service center. Price in my opinion a few dollars.

[mauro63]

You could start a small business doing this.
I would be interested.

The cost of shipping to Poland and back makes this business unprofitable.
They should be able to replace the sensor at the local electronics service center. Price in my opinion a few dollars.

Hi Krojan, very interesting, can you tell me the exact version of sht35 you have used?

Mauro

[krojan]

SHT35 is only available in a digital version with or without a filter. I bought SHT35-DIS-B here:
https://www.tme.eu/pl/details/sht35-dis-b/czujniki-wilgotnosci/sensirion/1-101388-01/

Italian side:
https://www.tme.eu/it/details/sht35-dis-b/sensori-dumidita/sensirion/1-101388-01/#

USA website:
https://www.tme.com/us/en-us/details/sht35-dis-b/humidity-sensors/sensirion/1-101388-01/#

[mauro63]

SHT35 is only available in a digital version with or without a filter. I bought SHT35-DIS-B here:
https://www.tme.eu/pl/details/sht35-dis-b/czujniki-wilgotnosci/sensirion/1-101388-01/

Italian side:
https://www.tme.eu/it/details/sht35-dis-b/sensori-dumidita/sensirion/1-101388-01/#

USA website:
https://www.tme.com/us/en-us/details/sht35-dis-b/humidity-sensors/sensirion/1-101388-01/#

Many thanks Krojan, I will try

Mauro

[krojan]

I wonder if FineOffset / Ecowitt is going to mount SHT35 in its sensors?

[mauro63]

I wonder if FineOffset / Ecowitt is going to mount SHT35 in its sensors?

absolutely not, for the moment, there are no plans about this now

Mauro

[krojan]

I wonder if FineOffset / Ecowitt is going to mount SHT35 in its sensors?

absolutely not, for the moment, there are no plans about this now

Mauro

Is this Lucy's official answer or your guess?

[mauro63]

I wonder if FineOffset / Ecowitt is going to mount SHT35 in its sensors?

absolutely not, for the moment, there are no plans about this now

Mauro

Is this Lucy's official answer or your guess?

I'm in costant contact with Lucy and updated about new products or improvements, but I can ask directly to have an official response
For example there are some improvements to ws80, I will explain later

Mauro

[krojan]

If they write us more to Lucy, maybe they'll take it into account.

[Mandrake]

I suspect its more about cost versus performance.
Producing consumer electronics is all about profit margin and I suspect it makes no sense to the average Joe about having a higher fidelity sensor installed if that impacts costs.
Likewise Ecowitt could sell a 'pro' version of their products with the SHT35 but would they sell enough to us enthusiasts to justify the engineering cost and then that would also cannibalise the normal product line sales.

I think its very unlikely at this stage but not impossible.
Fine Offset are clearly going upmarket with their technology options and products so its possible in the future.
These are my own opinions and not those of FO/Ecowitt despite my close ties to Lucy and team.

[galfert]

I suspect its more about cost versus performance.
Producing consumer electronics is all about profit margin and I suspect it makes no sense to the average Joe about having a higher fidelity sensor installed if that impacts costs.
Likewise Ecowitt could sell a 'pro' version of their products with the SHT35 but would they sell enough to us enthusiasts to justify the engineering cost and then that would also cannibalise the normal product line sales.

I think its very unlikely at this stage but not impossible.
Fine Offset are clearly going upmarket with their technology options and products so its possible in the future.
These are my own opinions and not those of FO/Ecowitt despite my close ties to Lucy and team.

I totally agree! I would pay for an SHT35. But it makes no sense for FO to use the SHT30 when everyone else is using the SHT31. The least they could do is use and SHT30 and remove the firmware limitations of 10% - 99% RH and provide the full range.

[raffaello.dimartino]

Hi guys,
following what have already done krojan, I have done a bit more hacking on a DP50 unit:

http://www.kwos.it/joomla/weather-monitoring/articoli/136-wh31-o-dp50-con-sensore-esterno




DP50 and sensors like that, with an external SHT35 sensor
The modification consists into removing the internal SHT30 sensor and put a connector to send externally the i2c signals: SCK(SCL), SDA, VCC, GND.

Follow on the image attached.
1) Locate on the PCB the SHT30 chip called U5
2) Locate, just near the U5 the two pull up resistors called R8 and R9
3) Locate also the filter capacitor called C16
4) remove the protective paint over the PCB around the just found components.
5) eliminate from the PCB all the components found
6) now add four cables just where, on the image, I wrote SCK, SDA, VCC, GND (for GND you can use any place on the PCB set to ground)
7) you have all the i2c signals. You can install a little connector modifying the sensor case.

[galfert]

Very nice mod. Can you tell us more about where you got that cable with the blue tag. And the end with the metal cylinder is that homemade or part of the cable assembly? Where did you get all those parts? I understand that on the end you likely have an SHT85 or something like it (the SHT85 is an already mounted SHT35.) Did it come with that white filter? Please let us know more.

Thank you.

[mauro63]

Very nice mod. Can you tell us more about where you got that cable with the blue tag. And the end with the metal cylinder is that homemade or part of the cable assembly? Where did you get all those parts? I understand that on the end you likely have an SHT85 or something like it (the SHT85 is a mounted SHT35.) Did it come with that white filter? Please let us know more.

Thank you.

Hi Galfert, Raffaello is my friend and also staff part on Meteonetwork
the sensor is like this one and is an sht35

https://www.amazon.com/Dustproof-FS400-SHT3X-Temperature-Humidity-Stainless/dp/B07WV924M8

Mauro

[galfert]

Thank you Mauro and Raffaello!  Very interesting and useful looking part. SMD soldering scared me off because I don't have a hot air system. But this is a rather nice looking solution.

I would like to see a comparison with this modification and a standard WH31, especially above 90% RH to 100% RH.

[Mandrake]

Its a great hack!
I must admit I am tempted too.
With the WH31 its only 20$ or so should you make a mess up and not catastrophic so well worth the costs of the parts required to play me thinks!

[mauro63]

Thank you Mauro and Raffaello!  Very interesting and useful looking part. SMD soldering scared me off because I don't have a hot air system. But this is a rather nice looking solution.

I would like to see a comparison with this modification and a standard WH31, especially above 90% RH to 100% RH.

Link at Raffaello's comparision test Page

http://www.kwos.org/comparison/

I hope he will not kill me for sharing
Pay attention, this is not a good time for temperature comparision, pay attention also to the firmware limitations about wh31 humidity read
Sorry for my English

Mauro

[raffaello.dimartino]

Thank you Mauro and Raffaello!  Very interesting and useful looking part. SMD soldering scared me off because I don't have a hot air system. But this is a rather nice looking solution.

I would like to see a comparison with this modification and a standard WH31, especially above 90% RH to 100% RH.

Hi Mauro and galfert,

Now I installed the SHT35 external inside a Davis 4 plates screen, the one that is used under the aerocone.
This is not the right period of the year to do comparisons.

If you don't have the hot air soldering station, you can try to remove the SHT chip with a very thin tip, jumping around the chip.

Or in this way:
https://www.youtube.com/watch?v=xMXJTLWyBCo

[fkapp]

Has anyone run a field comparison of the SHT 35 vs the SHT 31?
Wondering how these compare?

[raffaello.dimartino]

Has anyone run a field comparison of the SHT 35 vs the SHT 31?
Wondering how these compare?

To make a precise and scientific comparison between these two sensors, a high-precision climatic chamber is required.
The differences can also be minimal and would be observed above all at the extreme limits of their range curves.

Another possibility, but less precise, could be to have the two sensors in two identical screens.

At the moment I have moved my setup, but I have had this situation for months and I tell you, that there was no big difference in the temperature range of my area. It was always in the order of 0.1 degrees celsius which is also a limit to the accuracy of the instrument which means that they were almost the same.

I didn't notice any big differences in humidity either.

My field comparison is this: http://www.kwos.org/comparison