Searching for Portable Flow Meter


Thread Starter

Mark Hill

Greetings all;

I'd like to measure water flow through 6 and 8 inch plastic piping. The water contains a very small amount of suspended solids.

Does anyone have experience with portable flow meters ??

I'd like to find something with 4 to 20 mA output, powered by 110 VAC, and is relatively inexpensive to buy/rent.

Thanks in advance.

Mark Hill
[email protected]
If it is rigid plastic piping (Schedule 40 or Schedule 80 or Schedule 300 PVC) it is very easy to measure. If it is either HDPE or LDPE, consult your manufacturer of choice for special instructions. YOu can do it several different ways, both inexpensively and not so inexpensively.

The method depends quite a bit on what you mean by "a small amount of suspended solids."

If you mean less than 100 mg/l of greater than 200 mesh (75 micron) solids, you can do it either of three ways:

-- a hot tap insertion turbine or paddlewheel or insertion point magnetic flow sensor (prices vary between $500 and $2000...depending on accuracy
-- an insertion multipoint pitot tube or magnetic flow meter which can be hot tapped and removed for easy portability, leaving the tap for later.
-- an ultrasonic portable clamp on flow meter of the transit time variety.

Insertion turbine, paddlewheel and magnetic flow sensors, hot tapped, can be easily portable, and can give you a realistic performance somewhere in the 2-5% of span accuracy range, although some manufacturers may elect to tell you that they can perform better than that.

Insertion multipoint meters, of either the magnetic or averaging pitot tube variety can give you an accuracy installed with some care in the range of 1% of indicated rate, above 20% of span, and 1% of span below 20% of span.

Transit time ultrasonic flow meters can be extremely accurate: on the order of 0.1% of rate, but of the types listed here, are much the most expensive.

If the "very small amount of suspended solids" is larger than 100 mg/l or the particle size is greatly in excess of 200 mesh (75 micron) on average, the best alternative is a doppler ultrasonic flow meter. The normal installed accuracy of these devices is approximately 2% of span, regardless of manfacturers' specifications.

Several manufacturers of transit time and doppler meters lease their units. Most people buy them however, because they are useful tools to have around.

Hope this helps.


Walt Boyes

Contributing Editor, Flow Control Magazine

Walt Boyes--MarketingPractice Consultants
21118 SE 278th Place - Maple Valley, WA 98038
425-432-8262 home office - 253-709-5046 cellphone
eFax: 801-749-7142 - email: [email protected]

Paul Hamilton


With regard to your flow meter query Rosemount has a good portable flow meters, it might pay to give them a call.

They may be a little more expensive but usually deliver a more accurate measurement of flow whilst having a relatively longer life span than most other brands.

Hope you find what you are looking for!

ultrasonic flowmeters with clamp on attachments are commonly used for this purpose in the energy and hvac industries. see the web sites for controlotron and panametric and others. some utilities have loan scheme in their dsm departments which make loans, eg pacific gas and electric in san francisco has a loan scheme run thru their pacific energy center.


ps dsm = demand side management.
Give panametrics a try. They have units for both portable and permanent installation, 110 VAC power with isolated 4-20 ma output. Relative inexpensive they probably aren't, though. In the $4k range, if I recall.

Good luck.

Paul Yankello

Mark, There are basically two types of strap-on ultrasonic flow metering technologies availble for your application. The first being Doppler
ultrasonic flow meters. These meters require some amount of dirt, particulate, or aireation in the flow stream. The transducer emits a
signal and looks for reflection of that signal off the dirt, particulate, etc. Basically, it like standing on a railroad track. As a train
approaches you the pitch or frequency or the whissel changes as the train goes passes. This is how the doppler frequency shift ultrasonic
flow meter works. This technology does have some limitations. (1) It will not work on clean fluids. (2) The flow profile in the pipe is
faster in the center (center of pipe) than it is at the edge (close to the wall of the pipe). The doppler meter does not know if it has
reflected on a piece of dirt at the center or the edge. Where every it hits the particlulate you get this as a reading. The other technology is the transit-time ultrasonic method. This meter works well on both clean and dirty fluids. This metering technology measures the phase shift of the ultrasonic signal not the frequency shift. Basically it like this, you have a transmitter/receiver sensor on one side of the pipe and a transmitter/reciever on the other side of the pipe. The transcever produces a signal (we will call T1)which is shot across the profile of the flow and received at the other side of the pipe. The transcever at the other side of the pipe then send a signal back (will call T2), and so on and so fourth. The signals are emitted at the same frequency (eg 640 khz). However, the sonic velocity of the fluid creates a phase shift of the two signals (T1 and T2)as it fights accross the flow profile and travels with flow profile. This frequency shift is equal to fluid velocity. Knowing the Area of the pipe we can calculate the floe Q=V X A. Its hard to discribe with out a sketch. The easy way to think of it is as a time difference. If you were in a boat and crossing a lake with the current, it would take you T1 to get accross the lake. If you were to take the same route back fighting against the current it would take you T2. Knowing T1 and T2 we can now calculate velocity. Knowing Area we can now calculate flow Q= V X A. The advantage of this technology is that (1) it works in both clean and dirty liquids and (2) it take a chordal velocity measurement accross the flow profile which is more accurate. The portable doppler meter can range in price from $1250.00 to $3800.00 USD and the transit-time meter can range from $1250.00 to $9000.00 USD depending on options, pipe size capabilities, etc. We handle both technologies, if your application is still valid or you would like addtional info, check out or web site at - I hope this helps you out!!