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Weather Station Hardware => Davis Instruments Weather Stations => Topic started by: dport on July 13, 2018, 08:55:50 AM
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Any suggestions on a manual rain gauge to help calibrate my VP2? I'm not really interested in the cocorahs for $38 as I really only plan to use it a handful of times to nail the calibration. Surely there is a somewhat accurate solution for under $15.
So many gauges on amazon though. Couldn't tell you which are accurate and which are not. Reviews are all over the place.
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I used a gallon milk jug with a small hole poked in the bottom corner and use putty to open or close the orifice to control the rate of flow. I also used a scale accurate to the gram to weight the water for the desired amount (1ml of water weighs exactly 1gram). Being gravity fed, the rate obviously starts high, then slows as it empties. The rate I used starts about 4-4.5" per hour, then drops to less than 1" by the time it empties.
If you're unfamiliar, the amount of water equaling 1" of rain for the VP2 is 544ml.
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I used a gallon milk jug with a small hole poked in the bottom corner and use putty to open or close the orifice to control the rate of flow. I also used a scale accurate to the gram to weight the water for the desired amount (1ml of water weighs exactly 1gram). Being gravity fed, the rate obviously starts high, then slows as it empties. The rate I used starts about 4-4.5" per hour, then drops to less than 1" by the time it empties.
If you're unfamiliar, the amount of water equaling 1" of rain for the VP2 is 544ml.
Great, good to know. This will be a little project for me tomorrow. Will measure out 544ml into a milk jug and slowly release into VP2. Should take 20-30 minutes if I use your desired rain rate. Let's hope it comes out close to 1 inch!
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I used a gallon milk jug with a small hole poked in the bottom corner and use putty to open or close the orifice to control the rate of flow. I also used a scale accurate to the gram to weight the water for the desired amount (1ml of water weighs exactly 1gram). Being gravity fed, the rate obviously starts high, then slows as it empties. The rate I used starts about 4-4.5" per hour, then drops to less than 1" by the time it empties.
If you're unfamiliar, the amount of water equaling 1" of rain for the VP2 is 544ml.
Great, good to know. This will be a little project for me tomorrow. Will measure out 544ml into a milk jug and slowly release into VP2. Should take 20-30 minutes if I use your desired rain rate. Let's hope it comes out close to 1 inch!
You can use the adjusting screws or if you have something like WL, you can adjust for the error there too. Always duplicate the test to make sure you've indeed got it where you want it (I did it ad nauseam).
Oh, don't forget to disable your PWS's internet connection while testing.... #-o
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I used a gallon milk jug with a small hole poked in the bottom corner and use putty to open or close the orifice to control the rate of flow. I also used a scale accurate to the gram to weight the water for the desired amount (1ml of water weighs exactly 1gram). Being gravity fed, the rate obviously starts high, then slows as it empties. The rate I used starts about 4-4.5" per hour, then drops to less than 1" by the time it empties.
If you're unfamiliar, the amount of water equaling 1" of rain for the VP2 is 544ml.
Great, good to know. This will be a little project for me tomorrow. Will measure out 544ml into a milk jug and slowly release into VP2. Should take 20-30 minutes if I use your desired rain rate. Let's hope it comes out close to 1 inch!
You can use the adjusting screws or if you have something like WL, you can adjust for the error there too. Always duplicate the test to make sure you've indeed got it where you want it (I did it ad nauseam).
Oh, don't forget to disable your PWS's internet connection while testing.... #-o
Yeah I was actually just thinking about that. I use the WifiLogger. I can easily disable uploads to WU, CWOP, etc, however, I am unsure how to disable the actual internal logging of my logger. Don't want to take it out of the console as I think I'll have to do a full set up again.
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I used a gallon milk jug with a small hole poked in the bottom corner and use putty to open or close the orifice to control the rate of flow. I also used a scale accurate to the gram to weight the water for the desired amount (1ml of water weighs exactly 1gram). Being gravity fed, the rate obviously starts high, then slows as it empties. The rate I used starts about 4-4.5" per hour, then drops to less than 1" by the time it empties.
If you're unfamiliar, the amount of water equaling 1" of rain for the VP2 is 544ml.
Great, good to know. This will be a little project for me tomorrow. Will measure out 544ml into a milk jug and slowly release into VP2. Should take 20-30 minutes if I use your desired rain rate. Let's hope it comes out close to 1 inch!
You can use the adjusting screws or if you have something like WL, you can adjust for the error there too. Always duplicate the test to make sure you've indeed got it where you want it (I did it ad nauseam).
Oh, don't forget to disable your PWS's internet connection while testing.... #-o
Yeah I was actually just thinking about that. I use the WifiLogger. I can easily disable uploads to WU, CWOP, etc, however, I am unsure how to disable the actual internal logging of my logger. Don't want to take it out of the console as I think I'll have to do a full set up again.
You don't need to remove the logger, just delete the rain totals in the console or thru your software after testing.
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I used a gallon milk jug with a small hole poked in the bottom corner and use putty to open or close the orifice to control the rate of flow. I also used a scale accurate to the gram to weight the water for the desired amount (1ml of water weighs exactly 1gram). Being gravity fed, the rate obviously starts high, then slows as it empties. The rate I used starts about 4-4.5" per hour, then drops to less than 1" by the time it empties.
If you're unfamiliar, the amount of water equaling 1" of rain for the VP2 is 544ml.
Great, good to know. This will be a little project for me tomorrow. Will measure out 544ml into a milk jug and slowly release into VP2. Should take 20-30 minutes if I use your desired rain rate. Let's hope it comes out close to 1 inch!
You can use the adjusting screws or if you have something like WL, you can adjust for the error there too. Always duplicate the test to make sure you've indeed got it where you want it (I did it ad nauseam).
Oh, don't forget to disable your PWS's internet connection while testing.... #-o
When I did this a while back duplicate tests would come back off by .01. ](*,)
Just kept doing several tests until it was tweaked just right.
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To calibrate you could do this without a calibrator. Level gauge especially direction tippers line up . Get a medicine dropper and adjust tippers to tip 4.2 ml per tip. Factory is 4.282 ml per tip, it's 1 or 2" per hr rate. I would shoot for more and adjust tippers starting at 4.2 maybe even 4.1 ml to tip buckets.
Doesn't help finding manual rain gauge but checking and tweaking calibration this may help someone.
Here is where I found the numbers. http://www.emesystems.com/davis/documents/D7852%20Installation.pdf
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To calibrate you could do this without a calibrator. Level gauge especially direction tippers line up . Get a medicine dropper and adjust tippers to tip 4.2 ml per tip. Factory is 4.282 ml per tip, it's 1 or 2" per hr rate. I would shoot for more and adjust tippers starting at 4.2 maybe even 4.1 ml to tip buckets.
Doesn't help finding manual rain gauge but checking and tweaking calibration this may help someone.
Here is where I found the numbers. http://www.emesystems.com/davis/documents/D7852%20Installation.pdf
Now I'm confused, CW2272 said that 544ml would equal 1 inch of rain in the VP2. That would come out to 5.44ml per tip. But you are saying 4.282ml is one tip?
It's early and I haven't had my coffee. I must be doing math wrong.
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Now I'm confused, CW2272 said that 544ml would equal 1 inch of rain in the VP2. That would come out to 5.44ml per tip. But you are saying 4.282ml is one tip?
Assuming you're in N America then 5.44ml per tip is correct - it's really not difficult to work out for yourself. Personally I hate the thought of calibrating with a medicine dropper for all sorts of reasons. Much better to allow a known large amount (eg 544g or ml) of - preferably distilled or rain (which would be kind of appropriate) - water to drip steadily through the gauge.
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Now I'm confused, CW2272 said that 544ml would equal 1 inch of rain in the VP2. That would come out to 5.44ml per tip. But you are saying 4.282ml is one tip?
Assuming you're in N America then 5.44ml per tip is correct - it's really not difficult to work out for yourself. Personally I hate the thought of calibrating with a medicine dropper for all sorts of reasons. Much better IMO to allow a known large amount (eg 544g or ml) of - preferably distilled or rain (which would be kind of appropriate) - water to drip steadily through the gauge.
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Having done a lot of Davis rain gauge calibrations a lot of different ways, including a burette in a lab stand, and an eyedropper, I concur with Johnd. Trying to do it with a dropper will just lead to a lot of frustration. In theory, it sounds great, in practice, not so much. I finally purchased a Novalynx calibrator.
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Thanks guys. Think I'm going to experiment with 500ml in a water bottle today. That equals 0.92 inches in the VP2. Will poke a hole or two with a pin to start.
I'm not terribly worried about being 100% accurate, but I do want to be within the 4% spec that davis cites.
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To calibrate you could do this without a calibrator. Level gauge especially direction tippers line up . Get a medicine dropper and adjust tippers to tip 4.2 ml per tip. Factory is 4.282 ml per tip, it's 1 or 2" per hr rate. I would shoot for more and adjust tippers starting at 4.2 maybe even 4.1 ml to tip buckets.
Doesn't help finding manual rain gauge but checking and tweaking calibration this may help someone.
Here is where I found the numbers. http://www.emesystems.com/davis/documents/D7852%20Installation.pdf
Now I'm confused, CW2272 said that 544ml would equal 1 inch of rain in the VP2. That would come out to 5.44ml per tip. But you are saying 4.282ml is one tip?
It's early and I haven't had my coffee. I must be doing math wrong.
My bad 4.2 must of been the .2 mm gauge, I gave the link address.
Anyway I disagree with the notion dropper doesn't work well. I use the Novalix calibrator also but once I know what is needed the dropper method works every time. It's quick, easy and accurate.
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The results are in! At least after two of my tests. Both tests achieved an average rainfall rate of about 4 inches an hour using 500ml in a water bottle with a pin hole at the bottom. So, we know that 500ml is supposed to equal 0.92 inches of rain in the VP2. Here are the actual results
Test 1: 500ml = 0.89 inches
Test 2: 500ml = 0.90 inches
Some water may have been left in the tipper from test 1 to test 2, that could account for the extra hundredth. Regardless, these numbers are technically within spec according to Davis. I will also say that I performed this test during the middle of the day with bright sunshine, temp of 87, and dew point of 62. Some evaporation may have occurred, but probably not enough to make a real different.
Now, the question is, do I even bother adjusting the screws? My calibration tells me I'm low by about 2% on my gauge.
*Edit*, just opened unit to see the tipper. It was about half full at the end of the 2nd test. I think I was probably spot on at about 0.895 inches per test. 0.895/0.919 = 2.61%
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Now I'm confused, CW2272 said that 544ml would equal 1 inch of rain in the VP2. That would come out to 5.44ml per tip. But you are saying 4.282ml is one tip?
Assuming you're in N America then 5.44ml per tip is correct - it's really not difficult to work out for yourself. Personally I hate the thought of calibrating with a medicine dropper for all sorts of reasons. Much better IMO to allow a known large amount (eg 544g or ml) of - preferably distilled or rain (which would be kind of appropriate) - water to drip steadily through the gauge.
Just for clarification, the dropper is merely to get both spoons to tip as close together at the specified amount required. Then you use a much larger amount to fine tune by moving both screws up or down the exact same amount to keep the spoons as close to the same volume as possible. This method can also help correct for a less than perfectly level placement.
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The results are in! At least after two of my tests. Both tests achieved an average rainfall rate of about 4 inches an hour using 500ml in a water bottle with a pin hole at the bottom. So, we know that 500ml is supposed to equal 0.92 inches of rain in the VP2. Here are the actual results
Test 1: 500ml = 0.89 inches
Test 2: 500ml = 0.90 inches
Some water may have been left in the tipper from test 1 to test 2, that could account for the extra hundredth. Regardless, these numbers are technically within spec according to Davis. I will also say that I performed this test during the middle of the day with bright sunshine, temp of 87, and dew point of 62. Some evaporation may have occurred, but probably not enough to make a real different.
Now, the question is, do I even bother adjusting the screws? My calibration tells me I'm low by about 2% on my gauge.
*Edit*, just opened unit to see the tipper. It was about half full at the end of the 2nd test. I think I was probably spot on at about 0.895 inches per test. 0.895/0.919 = 2.61%
I also kind of screwed myself with upload data. I disabled all uploads while testing, then zeroed out the daily rainfall in the console after testing was complete. Then, when I enabled uploads again it added the rainfall to CWOP, WU, etc. Bummed.
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Some water may have been left in the tipper from test 1 to test 2
You should always ensure both spoons are empty before starting a new test if you want consistency.
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The results are in! At least after two of my tests. Both tests achieved an average rainfall rate of about 4 inches an hour using 500ml in a water bottle with a pin hole at the bottom. So, we know that 500ml is supposed to equal 0.92 inches of rain in the VP2. Here are the actual results
Test 1: 500ml = 0.89 inches
Test 2: 500ml = 0.90 inches
Some water may have been left in the tipper from test 1 to test 2, that could account for the extra hundredth. Regardless, these numbers are technically within spec according to Davis. I will also say that I performed this test during the middle of the day with bright sunshine, temp of 87, and dew point of 62. Some evaporation may have occurred, but probably not enough to make a real different.
Now, the question is, do I even bother adjusting the screws? My calibration tells me I'm low by about 2% on my gauge.
*Edit*, just opened unit to see the tipper. It was about half full at the end of the 2nd test. I think I was probably spot on at about 0.895 inches per test. 0.895/0.919 = 2.61%
I disabled all uploads while testing, then zeroed out the daily rainfall in the console after testing was complete. Then, when I enabled uploads again it added the rainfall to CWOP, WU, etc. Bummed.
Are you sure you cleared the data? That shouldn't have happened. You may want to try again. If you're successful, the CWOP data should clear by itself, WU dunno.
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Now I'm confused, CW2272 said that 544ml would equal 1 inch of rain in the VP2. That would come out to 5.44ml per tip. But you are saying 4.282ml is one tip?
Assuming you're in N America then 5.44ml per tip is correct - it's really not difficult to work out for yourself. Personally I hate the thought of calibrating with a medicine dropper for all sorts of reasons. Much better IMO to allow a known large amount (eg 544g or ml) of - preferably distilled or rain (which would be kind of appropriate) - water to drip steadily through the gauge.
Just for clarification, the dropper is merely to get both spoons to tip as close together at the specified amount required. Then you use a much larger amount to fine tune by moving both screws up or down the exact same amount to keep the spoons as close to the same volume as possible. This method can also help correct for a less than perfectly level placement.
The dropper is really all you need if you know how much. That's the key and why the calibrator comes in handy you can select a volume of water knowing how many tips you expect.
Then check tippers and measure how much water they take to tip. Keep this information and share it Its all you need to recalibrate later.
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The results are in! At least after two of my tests. Both tests achieved an average rainfall rate of about 4 inches an hour using 500ml in a water bottle with a pin hole at the bottom. So, we know that 500ml is supposed to equal 0.92 inches of rain in the VP2. Here are the actual results
Test 1: 500ml = 0.89 inches
Test 2: 500ml = 0.90 inches
Some water may have been left in the tipper from test 1 to test 2, that could account for the extra hundredth. Regardless, these numbers are technically within spec according to Davis. I will also say that I performed this test during the middle of the day with bright sunshine, temp of 87, and dew point of 62. Some evaporation may have occurred, but probably not enough to make a real different.
Now, the question is, do I even bother adjusting the screws? My calibration tells me I'm low by about 2% on my gauge.
*Edit*, just opened unit to see the tipper. It was about half full at the end of the 2nd test. I think I was probably spot on at about 0.895 inches per test. 0.895/0.919 = 2.61%
I disabled all uploads while testing, then zeroed out the daily rainfall in the console after testing was complete. Then, when I enabled uploads again it added the rainfall to CWOP, WU, etc. Bummed.
Are you sure you cleared the data? That shouldn't have happened. You may want to try again. If you're successful, the CWOP data should clear by itself, WU dunno.
Ok once I cleared the "daily rain" AND "storm total" I am now reset to ZERO on WU and CWOP. Unfortunately, pwsweather.com is still showing the rainfall.
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Now, the question is, do I even bother adjusting the screws? My calibration tells me I'm low by about 2% on my gauge.
Definitely not would be my view. Best not to touch the factory settings at all IMO. It sounds like you're as close as you're ever going to get in practical terms to checking that the calibration of the gauge is properly within spec.
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Now, the question is, do I even bother adjusting the screws? My calibration tells me I'm low by about 2% on my gauge.
Definitely not would be my view. Best not to touch the factory settings at all IMO. It sounds like you're as close as you're ever going to get in practical terms to checking that the calibration of the gauge is properly within spec.
Yeah I'm leaning towards your viewpoint. I really wanted to test though because I read about some folks being 30-40% off from the factory. I'm so thankful mine is within spec.
Now, that said, I wonder if me being low by 2% has do to with actual rainfall not going into the bucket (but rather a water bottle with a pin hole). Also to note is that I averaged 4 inches per hour rate during my test. Perhaps if I used a rate of 2 inches per hour I would be at 0% error. Who knows.
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Now, the question is, do I even bother adjusting the screws? My calibration tells me I'm low by about 2% on my gauge.
Definitely not would be my view. Best not to touch the factory settings at all IMO. It sounds like you're as close as you're ever going to get in practical terms to checking that the calibration of the gauge is properly within spec.
Also to note is that I averaged 4 inches per hour rate during my test. Perhaps if I used a rate of 2 inches per hour I would be at 0% error. Who knows.
You averaged 4" per hour or started at 4? I start at 4 and by the time the jug is empty, it's about 1" per hr.
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Now, the question is, do I even bother adjusting the screws? My calibration tells me I'm low by about 2% on my gauge.
Definitely not would be my view. Best not to touch the factory settings at all IMO. It sounds like you're as close as you're ever going to get in practical terms to checking that the calibration of the gauge is properly within spec.
Also to note is that I averaged 4 inches per hour rate during my test. Perhaps if I used a rate of 2 inches per hour I would be at 0% error. Who knows.
You averaged 4" per hour or started at 4? I start at 4 and by the time the jug is empty, it's about 1" per hr.
I averaged about 4 inches an hour. It started north of 6 inches an hour. All said and done it took 16 minutes to dump all 500ml of water. Averages to about 3.4 inches an hour if you do math. So, I take back my original 4 inch per hour mark :)
Most of the rain we get from May through August is in the form of thunderstorms with heavy rainfall rates. I wanted it to be as accurate as possible for those instances.
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How accurate is your 500 ml measurement?
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How accurate is your 500 ml measurement?
In my opinion, very accurate. I used a 500ml water bottle (actually labeled as 500ml) for the test. I had a whole case. The actual amount varied VERY slightly from bottle to bottle. However, I dumped all the water out of one bottle, then measured exactly 500ml using a measuring cup for liquids that held 500ml. I poured this back into the water bottle and it filled it to the exact spot the rest of the bottles were filled to.
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Now, the question is, do I even bother adjusting the screws? My calibration tells me I'm low by about 2% on my gauge.
Definitely not would be my view. Best not to touch the factory settings at all IMO. It sounds like you're as close as you're ever going to get in practical terms to checking that the calibration of the gauge is properly within spec.
Also to note is that I averaged 4 inches per hour rate during my test. Perhaps if I used a rate of 2 inches per hour I would be at 0% error. Who knows.
You averaged 4" per hour or started at 4? I start at 4 and by the time the jug is empty, it's about 1" per hr.
I averaged about 4 inches an hour. It started north of 6 inches an hour. All said and done it took 16 minutes to dump all 500ml of water. Averages to about 3.4 inches an hour if you do math. So, I take back my original 4 inch per hour mark :)
Most of the rain we get from May through August is in the form of thunderstorms with heavy rainfall rates. I wanted it to be as accurate as possible for those instances.
Wow, that's cookin'. If I were you, I'd drop the average rate down to 1-2" and see what you get then. At that toad choking rate, you may have had some spill out, and maybe not, but I'd slow it down to be sure.
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Now, the question is, do I even bother adjusting the screws? My calibration tells me I'm low by about 2% on my gauge.
Definitely not would be my view. Best not to touch the factory settings at all IMO. It sounds like you're as close as you're ever going to get in practical terms to checking that the calibration of the gauge is properly within spec.
Also to note is that I averaged 4 inches per hour rate during my test. Perhaps if I used a rate of 2 inches per hour I would be at 0% error. Who knows.
You averaged 4" per hour or started at 4? I start at 4 and by the time the jug is empty, it's about 1" per hr.
I averaged about 4 inches an hour. It started north of 6 inches an hour. All said and done it took 16 minutes to dump all 500ml of water. Averages to about 3.4 inches an hour if you do math. So, I take back my original 4 inch per hour mark :)
Most of the rain we get from May through August is in the form of thunderstorms with heavy rainfall rates. I wanted it to be as accurate as possible for those instances.
Wow, that's cookin'. If I were you, I'd drop the average rate down to 1-2" and see what you get then. At that toad choking rate, you may have had some spill out, and maybe not, but I'd slow it down to be sure.
I literally can't make the hole any smaller (sounds like a personal problem). I used a pin and punctured one little hole in the bottom of the water bottle. May have to find something other than a water bottle.
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Now, the question is, do I even bother adjusting the screws? My calibration tells me I'm low by about 2% on my gauge.
Definitely not would be my view. Best not to touch the factory settings at all IMO. It sounds like you're as close as you're ever going to get in practical terms to checking that the calibration of the gauge is properly within spec.
Also to note is that I averaged 4 inches per hour rate during my test. Perhaps if I used a rate of 2 inches per hour I would be at 0% error. Who knows.
You averaged 4" per hour or started at 4? I start at 4 and by the time the jug is empty, it's about 1" per hr.
I averaged about 4 inches an hour. It started north of 6 inches an hour. All said and done it took 16 minutes to dump all 500ml of water. Averages to about 3.4 inches an hour if you do math. So, I take back my original 4 inch per hour mark :)
Most of the rain we get from May through August is in the form of thunderstorms with heavy rainfall rates. I wanted it to be as accurate as possible for those instances.
Wow, that's cookin'. If I were you, I'd drop the average rate down to 1-2" and see what you get then. At that toad choking rate, you may have had some spill out, and maybe not, but I'd slow it down to be sure.
I literally can't make the hole any smaller (sounds like a personal problem). I used a pin and punctured one little hole in the bottom of the water bottle. May have to find something other than a water bottle.
You may have missed what I said earlier, I used putty, rope putty to be exact (any will work), to put over the hole to reduce the diameter. Takes a little time to get the flow you want, but you will.
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Now, the question is, do I even bother adjusting the screws? My calibration tells me I'm low by about 2% on my gauge.
Definitely not would be my view. Best not to touch the factory settings at all IMO. It sounds like you're as close as you're ever going to get in practical terms to checking that the calibration of the gauge is properly within spec.
Also to note is that I averaged 4 inches per hour rate during my test. Perhaps if I used a rate of 2 inches per hour I would be at 0% error. Who knows.
You averaged 4" per hour or started at 4? I start at 4 and by the time the jug is empty, it's about 1" per hr.
I averaged about 4 inches an hour. It started north of 6 inches an hour. All said and done it took 16 minutes to dump all 500ml of water. Averages to about 3.4 inches an hour if you do math. So, I take back my original 4 inch per hour mark :)
Most of the rain we get from May through August is in the form of thunderstorms with heavy rainfall rates. I wanted it to be as accurate as possible for those instances.
Wow, that's cookin'. If I were you, I'd drop the average rate down to 1-2" and see what you get then. At that toad choking rate, you may have had some spill out, and maybe not, but I'd slow it down to be sure.
I literally can't make the hole any smaller (sounds like a personal problem). I used a pin and punctured one little hole in the bottom of the water bottle. May have to find something other than a water bottle.
You may have missed what I said earlier, I used putty, rope putty to be exact (any will work), to put over the hole to reduce the diameter. Takes a little time to get the flow you want, but you will.
Fair. Though, with most of our rain coming at heavy rates during the summer, I feel confident that my VP2 is at least not under reporting significantly like some others have stated. For reference, my unit was shipped in early June 2018.
May do some additional testing tomorrow once I can slow the flow of my calibration device.
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Now, the question is, do I even bother adjusting the screws? My calibration tells me I'm low by about 2% on my gauge.
Definitely not would be my view. Best not to touch the factory settings at all IMO. It sounds like you're as close as you're ever going to get in practical terms to checking that the calibration of the gauge is properly within spec.
Also to note is that I averaged 4 inches per hour rate during my test. Perhaps if I used a rate of 2 inches per hour I would be at 0% error. Who knows.
You averaged 4" per hour or started at 4? I start at 4 and by the time the jug is empty, it's about 1" per hr.
I averaged about 4 inches an hour. It started north of 6 inches an hour. All said and done it took 16 minutes to dump all 500ml of water. Averages to about 3.4 inches an hour if you do math. So, I take back my original 4 inch per hour mark :)
Most of the rain we get from May through August is in the form of thunderstorms with heavy rainfall rates. I wanted it to be as accurate as possible for those instances.
Wow, that's cookin'. If I were you, I'd drop the average rate down to 1-2" and see what you get then. At that toad choking rate, you may have had some spill out, and maybe not, but I'd slow it down to be sure.
I literally can't make the hole any smaller (sounds like a personal problem). I used a pin and punctured one little hole in the bottom of the water bottle. May have to find something other than a water bottle.
You may have missed what I said earlier, I used putty, rope putty to be exact (any will work), to put over the hole to reduce the diameter. Takes a little time to get the flow you want, but you will.
Fair. Though, with most of our rain coming at heavy rates during the summer, I feel confident that my VP2 is at least not under reporting significantly like some others have stated.
Okey dokey... Would not be my choice, but not my PWS either.
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A 1ml syringe is a handy tool (as opposed to an eye dropper) to initially get a rough feel for tipper operation, then feed a measured amount of water (measured using graduated glass cylinder) through the gauge and initially multiple runs at varying time spans trying to emulate the most appropriate rain rate. As a home made dripper, a garden variety adjustable irrigation dripper works fine. What I use as a counter to count the tips is an old WMII console.
For a 0.2mm tipper I run 425ml and top off the last tip with a syringe then compute the adjustment noting that you shouldn't adjust the whole adjustment if it is large as the dynamics of the tipper will change and you will get an over adjustment. If you require say a 18% adjustment (not uncommon) then go maybe 2 full turns of the screws then run the test again.
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Now, the question is, do I even bother adjusting the screws? My calibration tells me I'm low by about 2% on my gauge.
Definitely not would be my view. Best not to touch the factory settings at all IMO. It sounds like you're as close as you're ever going to get in practical terms to checking that the calibration of the gauge is properly within spec.
Also to note is that I averaged 4 inches per hour rate during my test. Perhaps if I used a rate of 2 inches per hour I would be at 0% error. Who knows.
You averaged 4" per hour or started at 4? I start at 4 and by the time the jug is empty, it's about 1" per hr.
I averaged about 4 inches an hour. It started north of 6 inches an hour. All said and done it took 16 minutes to dump all 500ml of water. Averages to about 3.4 inches an hour if you do math. So, I take back my original 4 inch per hour mark :)
Most of the rain we get from May through August is in the form of thunderstorms with heavy rainfall rates. I wanted it to be as accurate as possible for those instances.
Wow, that's cookin'. If I were you, I'd drop the average rate down to 1-2" and see what you get then. At that toad choking rate, you may have had some spill out, and maybe not, but I'd slow it down to be sure.
I literally can't make the hole any smaller (sounds like a personal problem). I used a pin and punctured one little hole in the bottom of the water bottle. May have to find something other than a water bottle.
You may have missed what I said earlier, I used putty, rope putty to be exact (any will work), to put over the hole to reduce the diameter. Takes a little time to get the flow you want, but you will.
Fair. Though, with most of our rain coming at heavy rates during the summer, I feel confident that my VP2 is at least not under reporting significantly like some others have stated.
Okey dokey... Would not be my choice, but not my PWS either.
Limited resources here at the moment. Like I said, will try to create a new calibration device tomorrow to slow the flow.
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To calibrate you could do this without a calibrator. Level gauge especially direction tippers line up . Get a medicine dropper and adjust tippers to tip 4.2 ml per tip. Factory is 4.282 ml per tip, it's 1 or 2" per hr rate.
My metric (0.2mm) Davis rain gauges tip at 4.8 ml on one side and 3.6 on the other. I know this is intentionally done that way by Davis. Are you saying it is better to adjust the screws so each side tips with the same volume of water?
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A 1ml syringe is a handy tool (as opposed to an eye dropper) t
Thanks for the term syringe correction... I have always called the device that came with my Novalynx a dropper when it's a medicine syringe with much larger opening vs a needle syringe.
https://www.amazon.com/Ezy-Dose-Calibrated-Medicine-Syringe/dp/B0040HH7VO/ref=sr_1_4_s_it?s=hpc&ie=UTF8&qid=1531651958&sr=1-4&keywords=10%2Bml%2Bmedicine%2Bsyringe&th=1
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Thanks for the term syringe correction... I have always called the device that came with my Novalynx a dropper when it's a medicine syringe with much larger opening vs a needle syringe.
How it works is that such syringes in medical or lab use are almost always used with a separate disposable needle. The fitting between syringe and needle is typically what's called a Luer fitting (probably Luer Slip in this case rather than Luer Lock). So what you have there is very likely a medical syringe but supplied without the disposable needles.
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I see. :-) I've went through 2 of these because the black etched numbers wear off.