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A tutorial on Paddle Flow Meters for Flow Measurement and Control

This article will look in detail at the Paddle Wheel measuring principle for flow measurement and control. Experts in Flow measurement, Bürkert, provide us with technical explanations of how the different types of paddle wheel flow meters operate and also which applications these different types of flow meters are suited to.

Understanding Paddle wheel flowmeters

Paddle wheel flowmeters may be differentiated by the material used for the paddle wheel (plastic or stainless steel) or on the basis of signal detection/evaluation (coil sensor, HT coil sensor, Hall sensor or optical sensor). This results in the different paddle wheel sensors; the measuring principles of these paddle wheel sensors will be described below.

Different types of Paddle wheel flowmeters

Plastic paddle wheel flowmeter with inductive detection and pulse output

A PVDF or PP paddle wheel with four moulded permanent magnets in the arms rotates on a precision, wear resistant ceramic spindle and two ceramic bearings. A Hall sensor detects the magnetic field of the rotating paddle wheel is placed outside of the fluid area. Two output signals are generated per revolution and the frequency changes proportionally with the speed of rotation of the paddle wheel. An integrated electronics board converts this signal to a square-wave frequency signal.Plastic paddle wheel (PVDF or PP) with inductive 1

Type 8011 Paddle wheel flowmeter

The Type 8011 Paddle Wheel flowmeter is for continuous flow measurement and is especially designed for use in neutral, slightly aggressive, solid free liquids.

Type 8011 paddle flow meter

Plastic paddle wheel flowmeter with inductive detection and sinusoidal output

A PVDF or PP paddle wheel with four molded permanent magnets in the arms rotates on a precision, wear resistant ceramic spindle and two ceramic bearings. A coil with a ferrite core, detecting the magnetic field of the rotating paddle wheel, is placed outside of the fluid area. The frequency and voltage change in proportion to the rotational speed of the paddle wheel and two positive signals are generated per revolution. The rotation of the paddle wheel generates a sinusoidal voltage signal in the coil proportional to the flow rate. This sensor is two-wire and requires no additional auxiliary energy supply. A connected, battery operated display unit allows operation independent of mains voltage.

Plastic paddle wheel (PVDF or PP) with inductive 2

Type 8012 Paddle wheel flowmeter

The type 8012 paddle wheel flowmeter is used for continuous flow measurement and is especially designed for use in neutral, slightly aggressive, solid free liquids. The flowmeter is available in 2 measuring principles; a magnetic measuring version and an optic measuring version which allows infra-red to be passed for use with liquids.

Type 8012 paddle flow meter

Plastic paddle wheel flowmeter with optical detection and pulse output

The paddle wheel is made of PVDF material and the spindle and two bearings are made of wear-resistant ceramic material (Al2O3). Two infrared transmitters (IR) and receivers are placed in the electronics housing outside of the medium area, separated by plastic which allows infrared radiation to pass through it. The rotation of the paddle wheel is detected with these IR diodes and the integrated electronics converts the reflected IR-Signal to a square wave frequency signal, proportional to the flow rate. This optical method allows the flow rate to be detected in media with ferromagnetic particles and to detect the direction of the flow.

Plastic paddle wheel (PVDF) with optical detection 3

Type 8039 Paddle wheel flowmeter

The type 8039 paddle flowmeter has an extra-large display and is specially designed to switch a valve and to establish a monitoring system or an On/Off control loop. This flowmeter allows for Indication, monitoring, transmitting and On/Off control – all in one device.

Type 8039 paddle wheel sensor

Stainless steel paddle wheel flowmeter with inductive detection and pulse output

This paddle wheel consists of stainless steel with very low ferromagnetic characteristic. The spindle is made of a high- tech ceramic or stainless steel and the bearing is made of PEEK or ceramic. Inside the top-mounted electronics is a HT coil with permanent magnets and electronics which converts the coil signal into a square wave frequency signal proportional to the flow rate. The frequency changes in proportion to the speed of rotation of the paddle wheel. Two positive output signals are generated per revolution. This method is particularly used for media with temperatures up to 160°C (320°F). Ferromagnetic particles and contaminants in the fluid do not restrict the range of application.

Stainless steel paddle wheel with inductive 4

Type 8030 HT Paddle wheel flowmeter

The 8030 HT paddle-wheel flowmeter is an INLINE flowmeter for use in high temperature application. The flowmeter is especially designed for use in neutral, slightly aggressive, solid free liquids and can handle fluid temperatures up to 160°C.

Type 8030 HT Paddle wheel flowmeter

For more information about Bürkert’s range of flowmeters, download their Flowmeter brochure below. Alternatively, visit Bürkert technical experts in the PIF Solution Centre.

Burkert Flow Brochure

Company Profile

Bürkert Fluid Control Systems

Bürkert Fluid Control Systems is a world-leading manufacturer of control and measuring systems for fluids and gases.

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