Flowmeters

Buying guide

What the measured medium settles before anything else

The first thing a buyer has to pin down is what the flowmeter has to read and under what conditions, because that decision eliminates most of the catalogue before any brand or price enters the picture. A variable area flowmeter, the clear rotameter with a float rising in a tapered tube, reads a clean gas or liquid at a glance and needs no power, but its accuracy depends on the fluid being what the scale was calibrated for. A thermal or Coriolis mass meter reads mass directly and holds its reading as temperature and pressure shift, which matters when the gas density is not fixed. Line size, pressure rating and the fluid's cleanliness decide which technology even applies, so a buyer starts from the medium and the operating range rather than from a model number.

Condition carries more weight on a flowmeter than on most laboratory instruments, because the reading is only as good as the last calibration. A used variable area meter is largely mechanical and ages gracefully, but an electronic mass flow controller drifts, and a unit sold without a recent calibration certificate has to be recalibrated against a known reference before it can be trusted for anything quantitative. What to verify on a used listing is the wetted-material compatibility with the intended fluid, the state of any seals, and whether the sensor has been exercised recently. Air samplers and microbial air samplers add their own check, the flow rate the head was set to draw, since a sampler that no longer pulls its rated volume misreports concentration. Where a listing leaves calibration history unstated, a buyer should treat the figure on the dial as nominal until verified.

Price sits across a broad band here. Units cost anywhere from EUR 37 to EUR 9.684, with the average landing near EUR 998. A bench rotameter or a single-channel gas flowmeter fits a modest budget and occupies the lower end, while a multi-point industrial flow meter or a process installation from a maker such as Endress+Hauser carries the upper figures. Used and refurbished units are listed for sale below the price of new equipment, which is where most of the catalogue sits. Comparing two listings is easiest within a single maker's range, where the model numbering tells a buyer what separates one unit from the next; across makers, the deciding figures are the flow range, the accuracy class and the wetted materials rather than the badge.

Types of Flowmeters

Which flowmeter types are listed here?

Among the listings that specify a type, the catalogue divides into a handful of recognisable groups. Variable area flowmeters, the tapered-tube rotameters, are the simplest, reading flow by the height of a float and needing no power or calibration electronics; a technician reaching for a quick visual check of a clean line uses one. Gas flowmeters and industrial flow meters cover the metered side, from thermal mass units to inline process meters sized for a production line, chosen where a recorded, repeatable figure matters more than a glance. The air sampler and microbial air sampler groups are a distinct family that happen to measure flow as a means to an end: they draw a known volume of air so that what is captured, whether particulate or viable microorganisms, can be quantified. Environmental monitoring equipment rounds out the sample, used where airborne contamination or emissions have to be tracked over time.

The microbial air sampler ties this category directly to microbiology and life sciences work. These samplers impact a measured volume of air onto an agar plate so that colony counts translate back into a concentration, which is the standard method for environmental monitoring in cleanroom microbiology and sterile manufacturing. In that setting a flowmeter underpins contamination control for cell culture and biomanufacturing, where the air feeding a laminar flow hood or an isolator has to meet a defined cleanliness class before any protein purification or aseptic handling begins. Gas flowmeters also feed the carrier and sheath streams in instruments further down the bench, metering the gas supply to a flow cytometer or the mobile phase pressure in bioprocessing rigs. The flow figure is rarely the end product; it is the quantity that makes a microbiology air count or a genomics sample-prep step reproducible.

The brands behind the flowmeter listings

The listed makers run Various, Endress+Hauser, GF Signet, King Instrument, Copley. The "Various" share reflects the long tail of single-listing and unbranded units common in the used market, while Endress+Hauser anchors the industrial process end, GF Signet the water and utility lines, and King Instrument and Copley the rotameter and air-sampling side. For a buyer, a maker's presence in the catalogue signals two practical things: how easy parts are to source, since established lines like Endress+Hauser keep spares in circulation, and how readily one model compares against another within the same range. Parts can be sourced via Questpair where a used unit needs a seal or a float replaced.

What a used flowmeter costs here

New, used and refurbished units are all listed, and 92 percent of the listings are used. Prices run from EUR 37 to EUR 9.684, averaging around EUR 998. That spread covers the gap between a bare rotameter and a fully calibrated process meter, so the figure a given listing carries depends far more on its type and completeness than on its age. Used and refurbished flowmeters are listed below the price of new equipment, which keeps the bulk of the catalogue affordable for a buyer matching a specification rather than chasing a brand-new unit.