How to choose a flow meter
By Grant, Inspection Tool Specialists. Reviewed November 2026.
Three things decide which flow meter you need: the liquid and whether it is clean, the pipe it runs in, and whether you need a portable check or permanent monitoring. Answer those and most of the range falls away. Pressure instruments are a separate choice, covered at the end.
Which method suits your liquid?
| Method | Suits | Limits |
|---|---|---|
| Clamp-on ultrasonic | Checking flow in a full pipe without cutting it, with clean liquids | Needs a suitable pipe material and wall, and accurate pipe data; less reliable where the liquid carries gas bubbles or solids |
| Insertion ultrasonic | Permanent monitoring in larger pipes, with the sensor fitted through a tapping | Needs a fitting in the pipe and installation work |
| Doppler ultrasonic | Liquids that carry particles or bubbles, which reflect the signal | Needs enough particles or bubbles; clean liquid gives no reading |
| Electromagnetic | Conductive liquids in a full pipe, including dirty liquids | Needs a conductive liquid; not suited to non-conductive liquids such as hydrocarbons |
| Oval gear (positive displacement) | High-precision measurement of clean, often viscous liquids | Needs clean liquid; a strainer protects the gears from solids |
What the meter needs to know
A clamp-on or insertion meter works out flow from the pipe itself, so it needs the outside diameter, the wall thickness, the pipe material and any lining. Measure these before you order and tell us the liquid. A wrong pipe entry gives a wrong flow, however good the meter is. Check whether the pipe runs full, because most ultrasonic and electromagnetic meters need a full pipe to read properly.
Portable or permanent?
A portable meter suits spot checks on pumps, branches and supply lines, and it moves between points. A permanent meter, usually an insertion or electromagnetic installation, suits continuous monitoring, billing or process control, where the installation and outputs matter as much as the meter.
Pressure, not flow
Digital pressure gauges and differential pressure meters measure pressure in air, gas and liquid systems. A differential meter across a filter shows when the filter is loading. Airflow and velocity meters measure air moving through ducts. For high-pressure testing, a digital gauge up to 400 bar is listed in our range. Pressure instruments and flow meters answer different questions, so choose by what you need to know.
Which flow meter should I buy?
| Application | Suggested starting point |
|---|---|
| Quick portable check on water pipes | FM-210V5 portable flow meter |
| Clamp-on kit for pipes from DN15 to DN2000 | T200H portable ultrasonic kit |
| Clamp-on for large pipes | TM601 clamp-on meter, or the TM601 Plus |
| Permanent insertion monitoring | ST501 insertion meter |
| Liquids that carry particles or bubbles | DUF901-EC Doppler meter |
| Conductive liquids in a full pipe | LDG-SUP-A100 electromagnetic meter, DN10 to DN1000 |
| High precision on clean liquids | LC Series oval gear meter |
| Filter or HVAC differential pressure | PCE-P05 differential pressure meter |
| Air velocity and differential pressure | DT-8920 airflow meter |
| High-pressure test, up to 400 bar | PCE-932 digital pressure gauge |
As a guide to our current range, including VAT: portable flow meters from about R9,400; clamp-on and insertion ultrasonic meters from about R18,400 to R75,000; electromagnetic meters from about R23,800; Doppler meters from about R108,000; differential pressure meters from about R5,900 to R9,200; digital pressure gauges from about R4,000. Prices change, so check the product pages and confirm the pipe data and calibration options before ordering.
Questions we will ask you
Tell us the liquid and whether it is clean, any solids or gas bubbles, the pipe material, outside diameter and wall thickness, any lining, whether the pipe runs full, the expected flow range, whether you need a portable check or permanent monitoring, and whether the readings are for billing or compliance, which affects calibration. With that we can recommend a meter and provide pricing.