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Rainfall Measurement with Digitally Output Signal

12/16/2020 5:20 AM

Hello Friends,

My client need a instrument to measure rain at their plant, they want to make underground water storage at their site. So, they want us to install an instrument which measure the rainfall in day and they need the digital signal to be sent out at their PLC / DCS system as well.

Please suggest an instrument which can measure and send digital signal at the output.

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#1

Re: Rainfall measurement with Digitally output signal

12/16/2020 5:41 AM
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#2

Re: Rainfall Measurement with Digitally Output Signal

12/16/2020 9:56 AM

I don't understand what they think they want to do with the data. Surely records of monthly average rainfall exist for the area.

Though you clearly need to sort the grain from the chaff: these are just a couple of google searches: One site claims twice the anual rainfall than the other???

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#3
In reply to #2

Re: Rainfall Measurement with Digitally Output Signal

12/16/2020 1:07 PM

Well it could be they measure the water depth in the underground storage, and monitor the rainfall by inches, they can then estimate how many inches of rain it will take to fill the tanks...then they can monitor the water level in the tank to see if it matches the amount of rainfall they have had or there's some leak or evaporation going on...knowing the average annual rainfall does not tell how many inches must fall to fill the tanks, you have to take into account the area of the catch basin and the amount of rainfall that occurs in that particular spot....the amount of water will also dictate the amount of water treatment necessary...

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#4

Re: Rainfall Measurement with Digitally Output Signal

12/16/2020 4:20 PM

It is customary on this forum to decline to do something to which an internet search engine is more suited.

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#8
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Re: Rainfall Measurement with Digitally Output Signal

12/17/2020 5:37 AM

Not really.

Just a few of you.

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#13
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Re: Rainfall Measurement with Digitally Output Signal

12/20/2020 1:49 PM

Please feel free to tell anyone who gives a damn.

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#14
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Re: Rainfall Measurement with Digitally Output Signal

12/20/2020 3:51 PM

I did.

I told all of you

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#10
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Re: Rainfall Measurement with Digitally Output Signal

12/17/2020 10:50 AM

Internet searches frequently lead to erroneous results, as illustrated by Randall's above post: One of his sources says: "Average Annual precipitaton 40.78", while another says: "Annual precip. 19.30". both apparently for the Washington , DC area.

That's a huge discrepancy!

Also, I agree with JE.

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#5

Re: Rainfall Measurement with Digitally Output Signal

12/16/2020 9:03 PM

20 years ago, a company that I worked for, had thousands of solar powered remote weather stations, polled every 15 minutes thru satellites. We used tipping buckets. Very accurate.

Only one failure I can remember. Magpie's nest.

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#11
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Re: Rainfall Measurement with Digitally Output Signal

12/17/2020 11:11 AM

I've had a Davis Vantage Pro 2™ Weather station for a bit over 8 years (visible on the internet at KCAPLACE21). It has a tipping bucket with a reed switch, as does the one you suggest.

There are a variety of trees nearby, and the funnel leading to the bucket does get plugged occasionally with debris from the trees, so it needs to be cleaned at least a couple of times a year.

If you live in an area where it snows, the funnel needs to be heated whenever the temperature gets below freezing.

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#6

Re: Rainfall Measurement with Digitally Output Signal

12/17/2020 12:44 AM

I recommend a good sensor and a versatile datalogger.

These are ultra-low power, very accurate & reliable, and can communicate with almost anything via cable, RF, optical, etc. That logger can even talk Modbus over cellular.

You can connect a water level sensor to include the storage tank's level with the rainfall data. The logger can also monitor flow rates, control valves, send alarm SMS's, etc.

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#7

Re: Rainfall Measurement with Digitally Output Signal

12/17/2020 1:37 AM

Simple method would be to purchase a wireless weather station that downloads a signal for daily rainfall to a computer and then package the daily value and send it to the PLC via any protocol that interfaces with their computer. Wireless signal is usually 433MHz or 918MHz.

Second alternative is to use the same weather station that outputs a bluetooth signal and do the same data processing.

A more expensive operation and one I installed at a mine was to use a rainfall measurement device that outputs either an analog signal or a digital pulse for each discrete rainfall value measured. This then interfaces to a Modbusplus Analog and digital remote slave interface which has its radio signal sent to an antenna, in my case we used a Yagi and directed it at another Yagi mounted on a control room which was connected to a modbus plus master remote IO controller.

The master controller then interfaced with an analog input card and a digital input card on a Bailey control system. The master and slave carried out the handshaking and radio protocol needed to obtain the signal. and the logic in the Bailey DCS did the tabulating and supplied the information to the Citect SCADA.

The display screen provided readouts in mm/hr, mm/Day, mm/Year and with calculations could provide cubic metres of water in a dam.

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#9
In reply to #7

Re: Rainfall Measurement with Digitally Output Signal

12/17/2020 5:39 AM

Could I find your answer on Google?

Oh.. maybe now I can.

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#12

Re: Rainfall Measurement with Digitally Output Signal

12/17/2020 2:29 PM

First, how much does the local (weather service agency) say the local rainfall is?

Second, where is the watershed in which the plant is located?

What are the known maximum, and average, intensities-per-hour?

How big is the watershed, and what kind of surfaces comprise it?

How big is each such surface?

How much does the local (Flood Control Authority) say is the spectrum of local rainfalls (for 5-, 10-, 20-, 50-, and 100-year floods)?

What is the (local government agency) that prescibes the acceptable method for calculating design volume capacities?

Etc., ...

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#15

Re: Rainfall Measurement with Digitally Output Signal

12/21/2020 12:09 PM

Digital: the tank is either full or it isn’t.

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#16
In reply to #15

Re: Rainfall Measurement with Digitally Output Signal

12/21/2020 12:28 PM

That's not Digital. That's binary!

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#17
In reply to #16

Re: Rainfall Measurement with Digitally Output Signal

12/22/2020 9:07 AM

Not at Dodman's Lane Level Crossing, it isn't.

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