Low Voltage Low-flow Flowmeter

I can think of several measurement techniques that could be used to measure 125 cc per minute liquid flow rate...

What would the mixture be?

i.e. would it need to be steralised, cleaned, is the liquid a pure liquid clean etc...?

What sort of accuracy and turndown are you looking for?

What output do you need...

so many questions........

John.

The mixture can be a mixture of water and chemicals that might include weedicides, fungicides, insecticides, fertlisers, growth retardants or growth stimulants.

Viscoisty would normally not be higher than for water.

Accuracy ideally would be within 10%.

We are looking for a flowmeter with digital readout.

Thanks

Try a pump by Promenent. I was wondering just how you were going to move such a low low flow. I think they offer a 12 volt with a digital display that can show Rate of Flow. And by using Calibration tube, you can test the rate of flow. You really don't want to over-dose some of those chemicals....

Yup, they make a meteing pump that will meet your needs. Send me your e-mail if you need selection help.

Try this.....

http://www.lmipumps.co.uk/pumps.htm

Surely you did not get an answer you were looking for. I am a farmer and would also have an application for such a flow meter.

Send me a note and I'll get you what ever you need for a metering pump. The pump is microprocessor controled and has a digital display that shows flow rate. What it really does is measure stroke volume and number of strokes per minute, converting them into a flow rate, in this case L per hour. But the scale is user selectable. The pumps operate on 12VDC or 24VDC. It is tough to measure such a low flow in any other way. A Cal tube allows you to varify if the pump says 1 L/minute, 1 L/minute is really flowing through the pump.

The requirement is to measure a continuous flow of water / chemical mixture, measuring around 8 liters per hour.

But, a metering pump will generate a flow of this order. Buying and using this, only for calibration and comparison purpose could be a costly affair. I think the participant Yogi is looking for some cheaper and reliable solution with 10% accuracy.

I think the only way to to generate and measure a flow of this order is by metering pump. And you could set the flow rate to the correct volume. And the flow will be measured continoiusly. Not cheap, but common enough to be durable/reliable and not so expensive as to be unafordable. Even if a seperate flow meter were made, what do you use as a low dosage pump? Something still needs to move the chemical. An insulan pump might work, but the cost....

I agree with your point.

Referring to Yogi's note dated 10/04/2006, the flow liquid is, "The mixture can be water and chemicals that might include weedicides, fungicides, insecticides, fertilizers, growth retardants or growth stimulants".

It look like this soulution is to be prepared and injected along with flowing water to plants, for an application like drip irrigation. If this is the situation, one doesn't need to measure, it is good enough to set the metering rate to 8 lit/hr and inject to main stream. Yes, a metering pump has to be bought.

If water has to feed from a over head tank (of reasonably big in size), we may think of batch addition to this OH tank. By this we may get away for the need of a metering pump. If yogi wants to know of this option, let us discuss of this.

The need is for a low volume spray system we manufacture. We get current low flow rates by using a by-pass system from the pump to get rates to spray heads down low.

Metering pump trials - even at low volume, high stroke rates - gives some pulsing which we want to avoid. Additionally the pumping system has to be able to go as low as 8 lph but as high as 48lph so a metering pump has some problems, whereas a higher volume pump with adjustable bypass gives the flexibility as well as maintaining tank agitation.

The reason for the initial question was that an electronic flow meter could get over our problem of having some chemical mixtures that make use a visual flow indicator difficult.

Check out magnetic flow meters.It h as been a while since I have dabbled in this field, but they can measure any conductive fluid by imposing a magnetic filed on the moving liquid and measuring the voltage generated.You can use this signal for controlling a flow valve via a user adjustable set-point controller.No pulsations.Can even incorporate a strip-chart recorder for monitoring the flow unattended.Totalizers can also be easily incorporated, as well as many communication protocols.

Obenay N Pebvk

Surely a peristaltic pump would fit your needs well...?

They can be speed adjusted over a wide range, from very slow and low flow rates right up to high speed and highish flow rates...

The advantage is also that the media is contained within the tube, so contamination is avoided and if dirt or muck builds up its easy and cheap to just change the pumping tube.

John.