Flow Meter

A flow meter is used to measure the flow rate or volume flow in a pipe. It often doesn't matter whether the medium is gaseous or liquid.

Flow meter for liquids

The flow meter is installed in the pipe or the clamp-on sensors are mounted on the pipe. The flow meters are used in heating and air conditioning technology to check whether all the volume flows, generated by the pumps, are correct. Furthermore, the flow meter together with a data logger thermometer is able to calculate the amount of heat.

Which flow meter is right for my application?

The flow meters of the PCE-TDS 100 series differ basically only by the choice of the sensor, which is included in the standard scope of delivery. So, this is standard for this flow meter to measure the volume flow and the flow rate of liquids in pipes with the diameters:
- 20… 100 mm
- 50… 700 mm
- 300… 6000 mm

The sensors also differ in their design. For the flow meter there are sensors that are separate from each other and can be freely mounted on the pipeline and there are sensors that are mounted in a mounting slide that makes it easier to align the sensors axially to one another. Since the handheld device of the flowmeter is always the same model, different sensors can be connected to the flowmeter depending on the application. If the flow meter is used together with a thermometer, the amount of heat can be calculated. For this purpose, PCE Instruments offers a set consisting of a flow meter, a data logger thermometer and software, specially programmed for this purpose. The software is able to read-out the measurement data from the flow meter and the temperature measuring device and to calculate the amount of heat from the flow rates as well as the flow and return temperatures.

Flow meter for gaseous media

A flow meter for air and gases is usually installed in the pipeline or flow channel. Depending on the design, the flow rate is measured differently by the flow meter. Here, various measuring principles help to determine the measured value:
- impeller
- hot wire
- Pitot tube

The type of measurement principle is selected depending on the application.
The impeller is often chosen for simple testing tasks. The simple structure ensures that the flow meter of this type is comparatively inexpensive and the operation is very easy. The flow meter with impeller is simply held in the air flow and an indicator on the flow meter shows the flow rate. A disadvantage of this flow measuring device is that the access in the flow channel must be comparatively large and the flow meter itself generates a relatively high back pressure.

The hot wire flowmeter, on the other hand, has a very small sensor tip that can be inserted through the small openings in the flow channel. The sensor is often connected to the display device via a cable. Thus, the entire measuring device does not have to be put into the channel and the read-out from the display becomes considerably easier. The flow meters of this type are also particularly suitable for very small volume flows and flow velocities, as the sensor of the flow meter is very sensitive.

Flow meters with a pitot tube work according to the differential pressure method. The flow meter measures the ambient pressure and the inflow pressure of the medium via the Pitot tube. Through the calculation, the flow meter can measure in such a way the flow velocity and, after entering the channel area, the volume flow. Flow meters with Pitot tubes are typically used in channels where high flow velocities prevail or contamination caused by dust complicates the measurement with the other measurement methods.

Should you have any further questions regarding the application of the flow meter, please do not hesitate to contact us.

The device got its name due to its ability to operate in the ultrasonic frequency range and to register what is going on when the ultrasonic waves and acoustic oscillations go through the flow of liquid / gas. The faster the material moves / flows in the pipe, the more the frequency of the wave changes. In fact, by measuring the acoustic effects, the device determines the volume and consumption / flow of a certain material (water, oil, gas, various flowing products). The medium is flowing in the pipe at different speed, and the measurement carried out both, along and against the flow (upstream and downstream) is meant to determine, in the end, the flow rate and volumetric flow. There is no big difference in measurements if there is no flow, but with the increase of the flow, it is much more difficult for the wave to move against the whole flow than down the flow, and that is why the quicker the flow in the pipe becomes, the bigger the difference in up- and downstream measurements will be (different time required for passing a certain distance at certain velocity). Introduction of the acoustic transducer reacting to the density of the medium, provides that even the mass flow can be measured. A lot depends on the liquid, the flow of which should be measured. If the material is clean, the high frequencies are applied, and there is guaranteed a very reliable and accurate measurement to expect. If there are some solid particles in the liquid, spread unevenly, or the material is not clean enough, the frequencies should be lowered, to avoid their scattering and absorption of oscillations.

An ultrasonic flow meter is easy to operate and handle, it is a stable instrument, that has no moving parts and is quite robust with a long-term service life, nevertheless before its application, it is necessary to carry out the check of the liquid flowing so that to avoid uncertainties and failures during the measuring process. When applying flow meters, it should be taken into account that if some materials / liquids are very resistant to ultrasonic waves and reflect them rather than let them pass through, the measurement will be very inaccurate and errors may occur. The particles that may be present in the material have their own speed, different from the whole flow, in which they are in, and theoretically, this also may bring to big fluctuations and errors in the measurements of the flow rate. In spite of the possible difficulties, it is fair to say that modern ultrasonic devices have reached such a level that they cope even with such obstacles as very obscure and inhomogeneous liquids.
The range of application possibilities of an ultrasonic flow meter is high: almost all kinds of industry where the material is flowing in the pipes, most spread in water / wastewater, food and beverages producing industries, pharmaceutical, chemical and others.
Ultrasonic flow meters have got evident advantages which are very valuable and make it an irreplaceable tool when it goes about maintenance and service checks, as well as for measurement which should be preferably carried out without intrusion into the pipes. Depending on the material and kind of enterprise the measurement is carried out at, intrusion into the pipes may be quite undesirable (power or chemical plant), that is why application of non-contact meter that measures the flow of sometimes hazardous substance is very convenient. The flow meter with the clamp-on transducer may be even mounted on the pipe, and carry out the measurement externally, from outside, but there are a few things to pay attention to: it should be mounted and applied on the pipe correctly to avoid the weakening or loss of the ultrasound signal so that the latter was be able to fully reach the liquid. Application of the clamp-on transducer makes it possible to apply the device anytime, not depending on the kinds of liquid and its properties, since the device remains dry and not damaged. The measurement is carried out continuously and the results can be received in real time.

A mobile / portable ultrasonic flow meter facilitates the measurements to such an extent that an operator does not require any additional instruments for carrying out immediate checks wherever it is necessary (from water to oils and chemicals). It is ideal for the situations when quick measurement should be carried out for detecting a problem or just checking the general condition of the ongoing process. Due to the rechargeable battery pack the portable device ensures a few hours of regulative work and the internal data logger stores the measurements for further analysis and processing. Mobile flow meters can always be used as a reference for fixed installed flow meters, since, in spite of their compactness, they provide good measurement results.

One of new application fields is the application of a flow meter for HVAC control. Since nowadays there are strict requirements and regulations as for heating, air conditioning and ventilation, especially in closed spaces, rooms, offices and similar, the necessity to carry out accurate measurement of the air flow is quite high. For this type of measurements, temperature becomes an important parameter and the measurement is carried out taking a thermal flow principle into account. The best solution, when it goes about measurements in heaters, heating systems, fire extinguishing systems is a clamp-on heat meter. Without extra invasion into the pipe with hot / cold substance inside, the meter is fixed on the pipe (the size of the pipe does not matter) and allows carrying out the monitoring in the most difficult to reach and hazardous parts.
Application of the flow meter helps not only to find out the problems and carry out troubleshooting in the pipes, it provides possibilities for monitoring and quality control (for example, in beverages production, or analysis of the heating equipment and installations). If the device has got dual or multichannel option it makes it possible to carry out simultaneous measurements not only at a few points of one pipe, but also in a few pipes, thus providing better accuracy and possibilities to compare the values. Either clamp-on and whetted transducers can be used to make the measuring process more convenient and they are suitable for both, low and high operating temperatures, which ensures the application for monitoring of the cooling as well as for the heating systems.