Topic: Stratus gauge

[CW2274]

Just as an FYI, I bought a new stratus tube only, as I scratched the inside of my other trying to clean the inside, which wasn't difficult to do.    So, I thought I'd compare the two older ones I have against this newer one for accuracy. My two older ones with the meniscus at exactly 1" is 200 grams of water, which is as it should be with a four-inch catch. The new one, 204 grams, yes nothing earth-shattering, but certainly out of spec. The numerals were also slightly different looking as well compared to the older two. Am I trying to say knockoff, perhaps, but who knows. My two older ones I bought directly from Productive Alternatives, the OEM in MN, this new one from RainmanWeather. I'll be returning it and going back to the OEM.   

[CW2274]

I ordered another tube directly from Productive Alternatives and will obviously check. I question RainmanWeather on where their parts come from, and here's the reply...

Hello, to confirm all of our gauges and spare parts come directly from Productive Alternatives. Thank you for the clear explanation of the issue, I will forward your concerns to them and let you know of any replies. I will also inspect our stock to see if there is any difference noted between spares and also those included in complete gauges, will let you know the outcome of the audit.

Please let me know if I can be of any additional assistance.

Thank you,

Robert Ingham
RainmanWeather
14286 Beach Blvd.
Suite 19 #213
Jacksonville, FL 32250

Mods, if you want to move this to the Coco thread, have at it. Probably should have put it there in the first place. 

[WheatonRon]

I thought the conversion rate was 201 grams to an inch of water? I generally weigh the water in the 4” tube not including the inner tube and report that to CoCo. I have two 4 inch stratus gauges and the outer tube weighs slightly different between the two. Statistically insignificant in my view.

[CW2274]

I suppose 201 is acceptable. All I know is my two older ones are identical, the new one 2% different. Their stated accuracy is 1%. Like I said, nothing earth-shattering, but outta spec is outta spec. Evidently, RainmanWether sees it as a problem as well. Whether anything comes from it....

[miraculon]

I complained about the slot in the inner measuring tube not agreeing with the 1" marking due to surface tension. The point that it drains at is higher than the 1" mark. I deliberately displace some water by shaking or whatever to get it into the outer cylinder then measure it on the scale, say 0.96", then use that to subtract from the accumulated total found in the outer cylinder.

What are you using to determine 1 Inch? The overflow or the 1.00" marking on the scale?

I didn't get much of a response from the supplier about this, and CoCoRaHS can't seem to be able to do much about it.

I think that the drainage slot needs to be revamped to eliminate this difference between overflow and exactly 1". Meanwhile, I'll just stick to my current method.

To answer the question, I have used 201 g for years and continue to do so. Although, I have to admit that I have not repeated this evaluation.

Greg H.

[ocala]

I complained about the slot in the inner measuring tube not agreeing with the 1" marking due to surface tension. The point that it drains at is higher than the 1" mark. I deliberately displace some water by shaking or whatever to get it into the outer cylinder then measure it on the scale, say 0.96", then use that to subtract from the accumulated total found in the outer cylinder.

What are you using to determine 1 Inch? The overflow or the 1.00" marking on the scale?

I didn't get much of a response from the supplier about this, and CoCoRaHS can't seem to be able to do much about it.

I think that the drainage slot needs to be revamped to eliminate this difference between overflow and exactly 1". Meanwhile, I'll just stick to my current method.

To answer the question, I have used 201 g for years and continue to do so. Although, I have to admit that I have not repeated this evaluation.

Greg H.

On my old coco gauge I modified that slot to make it right. My new one I do what you do. Just stick my finger in it.

[CW2274]

What are you using to determine 1 Inch? The overflow or the 1.00" marking on the scale?

I'm using the meniscus at the 1" line, not the overflow, and that's with magnification from the glasses I wear when doing this. I've also noticed that the overflow line is even slightly higher with the new ones compared to the old ones.

I just received my second new tube....204. So I've now got two at 200, and two at 204. That said, I could see where 201 and 203 is observed by someone else, which would actually be at the 1% spec. Point being, they are definitely different, albeit slight. I can only assume Productive Alternatives switched molds somewhere up the road.

[ocala]

Did some testing on my end.
I started with Coco in 08 which is when the tube was bought.
1" weighs 195/196 after several tests.
Bought a new tube this past summer.
1" weighs 204 after several tests.
Tests were to the 1" line.
This was based on 200 grams.
Wasn't expecting it to be so different.
As I told CW in a PM a weight based rain collector would be the way to go.
I found this product but I'm sure it's way to expensive.
https://www.ott.com/products/accessories-109/ott-pluvio2-weighing-rain-gauge-963/

[CW2274]

What are you using to determine 1 Inch? The overflow or the 1.00" marking on the scale?

I've now got two at 200, and two at 204. That said, I could see where 201 and 203 is observed by someone else, which would actually be at the 1% spec.

Upon further review, I retract that statement. It's 200 and 204, no doubt, and yes, the scale has been verified for accuracy.  So, the guarantee, and it is, of 1% accuracy is out, and ocala's post above proves that even further. I'll wait to see if RainmanWeather gets back to me shorty and go from there.

[CSB]

Where are you guys buying these from and how accurate and easy to read are the new ones? I take it Stratus is the gauge of choice?
TKS, CSB

[miraculon]

I usually get my gauge parts from Weatheryourway.

Status is used because many here on WxForum contribute to CoCoRaHS. It is the "approved" gauge for CoCoRaHS.

It is also available from other suppliers: https://www.cocorahs.org/Content.aspx?page=store

Greg H.

[CW2274]

I just received my reply from RainmanWeather's query to Productive Alternatives about my query on the difference in tubes...

"There is no change".
Productive Alternatives

Really? I guess I and others are seeing things. Obviously, this person is unwilling to investigate further, and is blowing it off. This also constitutes fraud, as they guarantee 1% accuracy that's not being delivered.

[miraculon]

Either something has dimensionally changed (I doubt it), or there is a change to the polycarbonate material.

The former can be easily verified (i.e. the ID of the measuring tube) with a digital micrometer (or dial if you prefer).

I was wondering if there could be something about the polycarbonate plastic. (Rainmanweather's site says this, I can't confirm at Productive Alternatives)

I found this page regarding hydroscopic resins, sure enough polycarbonate is hygroscopic. I wonder if some material change, or variation in the material itself accounts for higher absorption of the water, thus increasing the mass of the tube.

Or, maybe the inner cylinder swells slightly when wet and changes dimensionally. Perhaps check the ID when completely dried out, then soak the cylinder and recheck?

Just musing on possibilities here....

Greg H.

[PaulMy]

As I told CW in a PM a weight based rain collector would be the way to go.I found this product but I'm sure it's way to expensive.

So I contacted OTT to see if that could be used to improve on snow precipitation measurement, and you were right... way expensive.


Enjoy,
Paul

[CW2274]

Interesting theories, however, I don't personally believe the material is responsible. Therefore, the dimension must have changed. The two newer tubes I have are the larger diameter, and have never been exposed to the elements. I just put old and new side-by-side, and the increments on the tubes are identical in height, which proves a slight change of inter dimension. I also just measured 1.00" in the old tube, carefully poured it into the new...0.985". Once again, must be a different dimension. No other explanation.

All I tried to do here is bring attention to a discrepancy. I'm not trying to "bring anybody down", but I would like some accountability, and a fix, but looks like that's not gonna happen. I mean, after all, this is "supposedly" our "gold standard", right?

Maybe they'll "sneak in" a fix without telling anybody. Sound like Davis and the SHT31 fiasco? Just sayin'...

[CW2274]

 Just in from RainmanWeather. Now THAT'S customer service! He sent a bunch of pics as well, but I'm not going to post them here, unless someone wants them.

Hello, I finally got time to experiment and was able to verify your findings. I had an older measuring tube that had been set aside at least a couple of years ago due to some stray ink marks on the side, I compared the older with one from our most recent shipment of spares. Firstly, I did not observe any physical difference in the markings other than the letters appeared a little darker and thicker on the newer one. I also noted after looking over the photos that the older has a clearer plastic, where the newer appears to be somewhat tinted. I weighed both and found them to be consistent 90g each. After zeroing the scale, I filled the older tube to 1” and found it to be 200g just as you had stated. Then the newer tube was filled to 1” mark and verified that it weighed 204g again just as you had observed. To truly verify, I then carefully poured the water from the new tube into the older and found that it filled noticeably above the 1” mark. My conclusion is that although there is nothing physical visibly different to the naked eye, and even the weight of the empty tube remains the same, apparently something has changed in the plastic molding to cause this difference. As there is no other physical difference noted, my assumption is that the wall of the tube has become marginally thinner causing this discrepancy.

 

I have confirmed your findings and will see to it that you receive a full refund for the replacement measuring tube that you were sent. If you have not yet returned it to us, I will send you a pre-paid return label or will reimburse you for the return postage.

 

 

Please let me know if I can be of any additional assistance.

 

Thank you,

 

Robert Ingham
RainmanWeather
14286 Beach Blvd.
Suite 19 #213
Jacksonville, FL 32250

[CW2274]

Okay.... just heard from Productive Alternatives as well! They informed me that their "molder" will be informed of the discrepancy, and will get back to me/RainmanWeather upon their findings. Sweet! Like my dad told me long ago.... the squeaky wheel gets the oil!

[miraculon]

Now, if they would only fix the overflow notch while they are at it....

Greg H.

[RainmanWeather]

Hi all, CW2274 alerted me to this thread, so thought I would drop on in. He has stated everything exactly where it stands at this point. The only thing to add is that I do believe miraculon is onto something and it is possible the plastic composition has changed somewhat which unintentionally introduced the difference. I suspect if that is the case, the current plastic composition is causing the inner tube diameter to be ever so slightly larger (curing differently?) thus accounting for the observed difference. I did try to measure the different tubes with a digital micrometer however did not have much luck getting consistent readings with the one on hand, it is going to require a very good precision instrument to verify.

[CW2274]

The only thing to add is that I do believe miraculon is onto something and it is possible the plastic composition has changed somewhat which unintentionally introduced the difference. I suspect if that is the case, the current plastic composition is causing the inner tube diameter to be ever so slightly larger (curing differently?) thus accounting for the observed difference.

Now that is something I could see. Being environmentally related to cause such a huge discrepancy seems over the top to me. But, who knows...

Thanks again for your backing!

[davidmc36]

.. it is going to require a very good precision instrument to verify.

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