Ultrasonic Flowmeter GHL Integration

[cpeguero]

Since I'm a bit of a data nerd and a scientist/engineer, I decided I wanted to measure the flowrate of my return pump to my display. I have a 260 gallon display, plumbed to my basement fish room that is also at the other end of the house. Vertical run is about 10 feet, horizontal is 40-50 feet, with a couple of twists and turns along the way. I run a Reeflo Hammerhead Gold, which, based on some back of the envelop calculations, (both assuming head and doing a quick stopwatch and watching it fill my tank) was giving me about 1500 gph. I figured measuring the flow could help me decide when it was time to service my return pump, or give me warning that something was wrong. 

 

Based on my assumed flowrate, I needed the highest range flowmeter GHL makes, 9000 L/hr. So, I get the flowmeter, and (as I knew before), it's a smaller diameter than my return piping. I run 1.5 inch return pipe, the ID of the flowmeter is about 1 inch. Now, I also happen to have studied fluid mechanics in school (and still do this for a living), so I know reducing my pipe diameter is not good. I though, perhaps, the GHL folks had done some work and found that a reduction like this for a small bit wouldn't have a big impact on flowrate...... Well, trust but verify, right? I set up my own flow loop with my backup pump and confirmed, as supsected, reducing to 1 inch diameter even for a small bit severely reduced the flowrate. Set aside some time to be irritated with the GHL folks (who's running that high a flow through 1 inch pipe?).

 

Now, I have a few options: 1 - run this in "bypass" mode, to minimize impact of reduction in flow. This requires a lot more plumbing and reduced probability of success; 2 - buy a second one and install both on my return after it splits at the DT into 2x 1 inch diameter pipes; 3 - find a 3rd party solution and make it feed into the Profilux. I chose option 3 for various reasons, primarily because I found an ultrasonic flowmeter for about the same price as the inline flowmeter from GHL. Bonus: I don't have to do any plumbing mods to use it.

 

Got the flowmeter (https://www.amazon.com/gp/product/B0BM4H9NPM/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) and ran it on my test flow loop to confirm I could configure it and get the same reading as the GHL flowmeter - success! Now comes the fun part - how do I make the 3rd party flowmeter feed a signal into the Profilux that will register as their own flowmeter? I figured they wouldn't just tell me how to do it, so I decided to figure it out for myself.

 

The GHL flowmeter hooks up to a 6-pin connector, whose pinout is available. Each 6-pin can connect to 2 level sensors or flow sensors. So 3 pins total used for a single flowmeter - 12 VDC, Level, and Ground. 

 

I found the likely OEM for the flowmeter, and looked at the output. Turns out the number of pins on the GHL-branded meter is different than the specs on the OEM.... I assumed they would at least keep the same signal output - OEM states 4-20 mA output. Great! The ultrasonic flowmeter has the same output. So, I try to hook up that output and..... nothing. No registered flow on the Profilux.....

 

Next step, see if I can probe the output from the flowmeter and figure out the signal. Luckily, a friend of mine is an Electrical Engineer, and had an oscilloscope I could borrow. We figured out that it's some sort of pulse, and through much trial and error, figured out all the flowmeter is doing is flipping a switch on then off once a certain amount of flow passes through the pipe. Big clue was the calibration factor in the Profilux software is in mL/pulse, but still took some tinkering to figure out it was that straightforward. 

 

Now, how do I turn the 4-20mA signal from the 3rd party flowmeter into a pulse? Convert the current signal to a voltage (https://www.amazon.com/dp/B07MYXVDDX?psc=1&ref=ppx_yo2ov_dt_b_product_details) (you can also do this with just some resistors, but since the output is 4 mA at 0 flow, you end up with a 2 volt output at 0 flow, which you can't zero out in the software). Great, now, turn that voltage into a frequency output (https://www.amazon.com/dp/B06XZY3B6D?psc=1&ref=ppx_yo2ov_dt_b_product_details). Hooked this up, thought I'd be great, but.... still nothing on the Profilux. Eventually, I figured out that it was switching too fast. The max frequency from the GHL flowmeter was around 1 kHz. So I needed a prescaler/frequency divider (https://www.ebay.com/itm/154654108784). I also got some solid state relays to make sure the relay could switch fast enough (https://www.amazon.com/dp/B07ZHC5M7H?psc=1&ref=ppx_yo2ov_dt_b_product_details) and needed to power the prescaler (https://www.amazon.com/dp/B07YXN8J6R?ref=ppx_yo2ov_dt_b_product_details&th=1). Some of the other items needed DC power, which was supplied by the flowmeter internal wiring (it has 28? volt DC inside the control box). 

 

Finally, I had everything together, and it works! To sum up, I'm taking the output from the flowmeter, which is 4-20 mA, converting it to a 0-10 Volt DC signal, converting the voltage output to a 0-10 kHz frequency signal, which is divided by 10 with the prescale, to produce a frequency output 0-1kHz. This is used to switch the solid state relay. That relay shorts between the 12 VDC pin and the Level pin. Each "pulse" registers in the Profilux, and I just needed to calibrate the input to know how many milliliters per pulse! Luckily, the ultrasonic flowmeter has a "virtual" mode, which simulates the output for whatever flow I put in. So I was able to quickly calibrate it, input that calibration into the Profilux, and viola! I now get my flowrate read into my Profilux. I figured I'd document all this here to save someone else the 2+ months (on the weekends and in between) that I spent figuring this out!

 

Also, I learned that my actual flowrate is about half what I thought it was - around 760-800 gallons per hour! I was counting on this to be a significant part of my flow in the tank, so I added a couple of MP40s to up the flow in the tank.

 

I hope someone finds this helpful. I certainly felt great finally figuring this out!