Jos Abbing
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Experiencing harsh industry applications for many years now, I have seen several unpleasant results of corrosion. The global corrosion costs are huge, more than 2000 billion Euros according to NACE. Almost 60% occurs in industrial use, with the chemical, process, and oil & gas industry accounting for the majority share.

These types of industries are coping with demanding environmental and process conditions in production and operation. This includes associated services, such as in heat-transfer systems, transmissions, and distribution and storage of gases and liquids. Prevention or control of corrosion by the use of inhibitors often proves to be an economic solution.

Using a low flow control system can help you dose more accurate amounts of corrosion inhibitors. Accuracy is crucial here; it greatly influences the efficiency and minimizes environmental impact of an inhibitor system.

General corrosion factors

In fact, all metals have a tendency to corrode or dissolve to some degree. Corrosion is a natural process converting metals to a more chemically stable form. The main process medium and the environment have a major impact on corrosion factors such as oxygen, water content, acidity levels, temperature and other factors.

Image description Corrosion Factors

Influencing these main drivers allow corrosion to be stopped or slowed down sufficiently and it is here that inhibiting can play an important role.

Desgining in corrosion resistantance by selection of best compatible material and combinations, additional material thickness, and application of protective coatings may have an initial technical preference to inhibiting. Additionally, metal damage by erosive particles, fatigue, mechanical stress or cavitation may cause corrosion processes which cannot be controlled sufficiently with the use of inhibitors.

However, prevention or control of corrosion by inhibiting often proves to be an economic solution in lots of other situations, improving life time and operational costs with minimum environmental impact. Some relevant examples are to follow.

Examples of metal corrosion

Corrosion can have different drivers and causes:

Image description Anode-cathode principle

Galvanic corrosion requires two different metals that are in electrical contact. When exposed to an electrolyte, a migration of ions from the anode to the cathode causes a release of free electrons. The more noble metal (cathode) is protected and the more active metal (anode) tends to corrode.

Electrochemical corrosion, involving the release of electrons of anodic parts, is related or involved in a lot more corrosion processes, such as concentrated cell (crevice) or pitting corrosion.

Another example is chemical corrosion, which is often induced by strong oxidants, and may not be accompanied by the flow of electric current.

Biological corrosion is caused by the presence and growth of micro organisms. Their direct presence or their corrosion product caused by metabolic activity of the organisms damages the metal which can also lead to pitting or crevice corrosion.

Inhibitor classifications

The task of an inhibitor substance is to slow down or prevent the damage caused by corrosion to acceptable levels. Most corrosion inhibitors used are multi-component mixtures. Below some important examples for (liquid phase) inhibitors.

Image description Inhibitor classification

Environmental or scavengers inhibitors control corrosion by reducing or removing the corrosive properties in the medium, often involving oxygen reduction.

Interface inhibitors form a protective film on the metal, isolating the metal from the corrosive medium.

Anodic inhibitor will facilitate the formation of passivation layer blocking the anodic process. The critical concentration of the inhibitor is important to secure effectivity and to prevent corrosion acceleration caused by a too high concentration of inhibitor.

Cathodic inhibitor will decrease the corrosion rate by reduction of oxygen concentrations or increase in the over potential of hydrogen liberation (poison) and precipitate (deposit) on specific cathodic areas (precipitator), forming a protective film.

Mixed or organic inhibitors can moderate both anodic and cathodic principle e.g. by adsorption, chemisorption and film formation. An adsorption processes (physical) is relatively quick but are also more easily removed from a surface, requiring careful control. Chemisorption is a chemical adsorption process, caused by a reaction on an exposed surface, creating an electronic bond of a chemical on the adsorbed surface. The higher the concentration the greater the protection with a limit to a maximum. By exceeding the maximum concentration, corrosion acceleration is often observed.

Enabling smarter dosing control

A corrosion inhibitor system will add small concentrations of (bio) chemicals into the process. The effectiveness of an inhibitor system greatly depends on the correct injection amount. The correct injection amount is also influenced by the environmental and process conditions.

Image description Ex Zone 1 scale inhibitor with Coriolis mass flow controller

The required weight fraction of traditional mix of biocides, other inhibitor substances, agents, surfactants and pH regulators may vary e.g. between 0.001 and 0.1 weight %. The inhibiting system may inject in parts per million (PPM) to achieve low concentrations to be effective. Both continuous and shot dosing systems are used, based on the situation.

Traditional methods often involve manually tuned piston pumps with check valves. Verification of flow, by changing the stroke length, is often carried out empirically with stop-watch and graduated gauges. This traditional approach makes it virtually impossible to actively compensate to changing process conditions, such as temperature changes (caused by day/night). The result may be the worst-case flow setting, increasing chemical use, environmental impact and also cause over-dosing (!) of chemicals under normal operation conditions.

Accurate flow control

Accurate flow control enables cost effective applications with less environmental impact. High accuracy and high turndown ratio is achieved based on pure mass measurement with mini CORI-FLOW. This mass flow meter can also directly control valves and pumps by on-board PID control and can be further optimized with PLC and HMI control extending both performance and flexibility.

Coriolis dosing system

Our Coriolis dosing system approach, with digital communication, enables real-time monitoring, control and logging of injection rates. This allows online checking of flow rates and instantaneous re-setting of the required flow rate. Asset management and preventive maintenance is supported with several active diagnostics such as on-board status alarms enabling, steering monitoring, density alarm changes, single or multi point totalization for costs calculations, empty tank alarm, and pump protection shut down.

Bronkhorst has been supporting field applications and R&D research projects with extensive know how on low flow fluid handling. The ongoing research for even more environmental friendly solutions, such as biodegradable based inhibitors, is gladly supported by us.

Corrosion inhibitors are also used in other kind of industries such as public water systems. Check our blog about how phosphates are added to our drinking water as corrosion inhibitor to prevent the leaching of lead and copper from pipes and fixtures.

Bronkhorst Coriolis mass flow controllers can be an ideal solution for corrosion inhibitors. Have a look at our Coriolis product line.

Rob ten Haaft
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It might surprise you but already since the Middle Ages, people are interested in the smell of a person’s breath. In those days it must have been quite a challenge to investigate but as early as those days diseases like diabetes (associated with a sweet, acetone odor) and liver failure ( a fish-like smell) were diagnosed upon one’s breath. I will not discuss the treatments during those years; let’s say that much has improved since the Middle Ages. For example, nowadays, we use Ion Mobility Spectrometers (IMS) to measure Volatile Organic Compound (VOC).

At the beginning of the 21st century, research studies show that dogs are able to detect cancer by smell. The dogs are trained to detect different kinds of cancer in exhaled breath of human patients, as they can smell with a sensitivity of parts per trillion (ppt). To give an example: the scent of one cc of blood, diluted in 20 Olympic sized swimming pools can still be detected by the dog. It was concluded that dogs are probably discriminating between breath samples based on a specific breath odor but it is still unknown what odor or mix of compounds dogs detect. The detection of cancer by trained dogs seems to be obvious when you think about it, but it requires a lot of training of the dogs and it is still unknown why not all cases of cancer are detected.

Volatile Organic Compound (VOC)

This is the reason that researchers have started to develop analyzers that can do the dog’s job. In the last few years it was discovered that Volatile Organic Compounds (VOC) can be distinctive biomarkers in the diagnosis of human diseases. Volatility is the tendency of a substance to evaporate, therefore Volatile Organic Compounds are organic compounds that will easily evaporate or sublimate at room temperature.

The exhaled human breath contains a few thousand volatile organic compounds and the composition of the VOCs is used in breath biopsy to serve as a biomarker to test for diseases such as lung cancer.

An increasingly popular analytical technique to measure VOC’s is Ion Mobility Spectrometry (IMS). This technique is ideal for analysis in medical applications since the analysis is fast, not affected by humidity, highly sensitive, and operates at ambient pressures. This makes the technique very suitable for portable or Point of Care application.

Ion Mobility Spectrometry (IMS)

The Ion Mobility Spectrometer operating principle is based on the drift, or time-of-flight, of ions that are formed in the reactant section. The ions travel, supported by an electric field, through the drift tube where they encounter a drift gas (N2 or Air). The shape and the charge number of the ion will make it easier or harder to flow through the drift gas which will cause a separation of the ions in the sample and after detection give an IMS-spectrum as shown in Figure 1.

Image description Figure 1 : Ion Mobility Spectrometer with spectrum

Mass Flow Controllers

To deliver the gases to the drift tube, Bronkhorst has the knowledge and experience to supply the right products. Our products address the specifications that are important for controlling the gases in Ion Mobility Spectrometry such as:

  • cleanliness,
  • small instrument size,
  • fast response, good reliability,
  • low power and
  • low cost of ownership. Our MEMS (Micro Electro Mechanical Systems) based instruments, such as the IQ+FLOW thermal flow meters, are very suitable for Ion Mobility Spectrometry.

Image description IQ+FLOW thermal flow meter

Are you interested to read more about mass spectrometry (MS) and how mass flow controllers and evaporation is used for Electrospray Ion source, check our blog ‘A closer Ion them’.

Check our success story using IQ+ gas flow meters and pressure controllers for a gas chromatography application.

If you have questions or ideas on Ion Mobility Spectrometry other analytical applications that involve controlling of gas or liquid, feel free to contact us.

Frank Doornbos
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The first variable area (VA) meter with rotating float was invented by Karl Kueppers in Aachen in 1908. The device was patented in Germany that same year. Felix Meyer was among the first to recognize the significance of Kueppers’ work and implemented the process for offering the meter for sale. In 1909, the firm of "Deutsche Rotawerke GmbH" was created in Aachen (Germany). They improved this invention with new shapes of the float and of the glass tube. It didn’t take long for the new device to capture attention in Europe, the United Kingdom, and other areas.

VA flow meters (or purge meters)

Over time, different types of VA flow meters (also called purge meters) have been developed, usually in response to some specific need. Nowadays a purge meter usually consists of a tapered tube, typically made of glass or plastic. Inside this tapered tube there is the ‘float’ which is made either from anodized aluminum or ceramic. The float is actually a shaped weight that is pushed up by the drag force of the flow and pulled down by gravity. The drag force for a given fluid and float cross section is a function of flow speed squared only.

While the meters are still relatively simplistic in design, relatively low cost, low maintenance and easy to install they are used in many kinds of application. Despite these facts, the traditional VA meter has a number of drawbacks. For instance, graduations on a given purge meter will only be accurate for a given substance at a given temperature and pressure. Either way, due to the direct flow indication, the resolution is relatively poor. Especially when they are built into a machine, reading might be hard. Moreover, the float must be read through the flowing medium, so you can imagine that some fluids may obscure the reading.

9 reasons why to use a thermal mass flow meter instead of a traditional purge meter

As for the current century, Bronkhorst has developed a thermal mass flow meter series (MASS-VIEW, as shown in picture 1) which is the digital high-tech alternative to the traditional VA flow meters. Thanks to today’s digital possibilities, many other advantages arise for many industrial processes and chemical plants.

bronkhorst-mass-view-flow-meter MASS-VIEW flow meter in application

  1. The MASS-VIEW flow meter series operate on the principle of direct thermal mass flow measurement (no by-pass); rather than measuring the volume flow it measures the actual mass flow, without the need of temperature and pressure correction.
  2. The digital OLED display provides an easy direct or relative reading of the actual flow. Herewith parallax errors are excluded.
  3. With this digital mass flow meter it is easily possible to obtain the accumulated flow. This availability of data gives insight in costs, leading to data driven decision making power.
  4. In contrast to the traditional VA meter which need to be mounted in a vertical position, this digital alternative can be mounted in any position.
  5. The flow path is made of sustainable aluminum rather than plastic or glass which is fragile.
  6. The instruments are standard equipped with 0-5V, RS-232 and Modbus-RTU output signals. Note that the traditional VA meters usually do not have any output signal available at all.
  7. As a standard feature, there are 2 built-in relays which indicate an alarm situation. Herewith, external devices can be controlled.
  8. Multi Gas; as opposed to traditional VA meters, which are produced for one particular fluid only, the digital alternative has up to 10 pre-installed gases available as a standard feature.
  9. Multi Range; traditional VA meters usually have a rangeability of 1:10 and one single full scale range only, the digital alternative has a rangeability of 1:100 as well as up to 4 pre-installed flow ranges.

Achieve a stable flow

A VA meter, whether it is a conventional or a digital one, can be equipped with a built-in needle valve. This needle valve enables the user to regulate the flow rate by means of a restriction inside the flow channel. As long as the inlet pressure is stable, the subsequent flow will be stable too. On the other hand, once pressure conditions are susceptible to change, the flow rate will become equally unstable. If this is not desirable, you’ll have to compensate these pressure fluctuations.

Flow control

Manual control valve

This effect can be eliminated by using a manual control valve like the FLOW-CONTROL series which keeps the pressure drop across the needle valve (delta-P) constant. This is accomplished by a second (normally open) valve, though it is operated by a membrane this time. The operating principle is based on a balance that forms between the pre-pressure, back-pressure and the spring force on the mebrane. A change in the pressure conditions leads to a change of the equilibrium and thus a change in the valve position as well (as shown in the picture below).

working-principle-control-valve Working principle of a pressure compensated control valve

Although Bronkhorsts’ pressure compensation technology is suitable for either gases and liquids, the nice thing about this is that both technologies, the digital VA meters and pressure compensation, lend themselves well to being built together. However, in that case it is applicable for gases only.

Learn more about the different models in the manual constant-flow control series

Hans-Georg Frenzel
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We all love cake, there’s no denying that, and especially with whipped cream. A celebration isn’t a celebration without a cake, whether you’re throwing a birthday party or attending a wedding. Or just when you’re having coffee with friends or family, simply because it’s delicious. Baking and decorating a cake takes a lot of time and patience. And that’s exactly why most choose the easy way of picking out an already finished piece , either from their local pastry chef or out of the freezer section at the supermarket. And today I would like to tell you something about how such a fancy cake is made.

Manufacturing the cake layers

It all starts with the base, which consists of one or more layers of cake that provide support to the whipped cream. These layers are factory produced, but they aren’t made in individual round spring forms. The dough is applied on a closed metal conveyor belt by using nozzles. This belt goes through an oven and at the end the individual shapes with the desired diameter are cut out of the dough.

Controlling air by using mass flow controllers

To make sure that these cake layers all have the same weight and consistency, foam technology is used in addition to the baking agent in the dough. In this case, a foam mixer generates a dispersion of dough and air which is then applied onto the baking steel belt. In this process, it is highly important that this dough always has the same consistency, density and quality. Thus it is not only necessary to control the delivery rate of the dough, but just as important is the amount of air. By using the Bronkhorst EL-FLOW Select mass flow controllers, precise control of the required air volume is ensured at all times throughout the whole process.

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EL-FLOW Select thermal mass flow controller for control of the air volume

Whipped cream

In cake decoration, the cake layers are covered with whipped cream and other sweet fillings. To produce whipped cream out of liquid cream, another foam mixer is used in combination with Bronkhorst mass flow controllers, proving their worth yet again by achieving continuous high accuracy and precise control. The whipped cream production is similar to dough production; however the requirements for this system are different.

Hygiene requirements: Cleaning in Place - CIP

In food production, high hygiene requirements apply. In the dough production process, the mixer is cleaned of residues by CIP (Cleaning In Place) using cleaning additives, guaranteeing a hygienic product. However, in whipped cream production, it’s highly important that all product-contacting surfaces in the foam mixer are clean and absolutely germ-free, since it’s a sweet dairy product and the cake needs to be preserved for a long period of time. This asks for even higher hygiene requirements, so these machines need a different cleaning approach. Using only CIP with cleaning additives can’t guarantee this, so they have to be sterilized in place (SIP) as well. Using a saturated steam at a temperature of 130° Celsius, the product area of the machine is thoroughly cleaned. This maintenance takes around 300 seconds to make sure all germs are killed. This gives the cake a longer shelf life when stored in the refrigerator or freezer.

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A Hansa Mixer installation

Hansa Mixer

Hansa Industrie-Mixer is a worldwide, medium-sized company that operates in the field of mixing machines and foam generators for the food and non-food industry. Technical equipment before and after the foam mixer is also included in the scope of delivery to the customers. These are not mass-produced products, but every system is customized and tailored to the needs of the customer. If you want to differentiate yourself from the competition, you need a custom-made machine and system. The heart of the foam mixer is a mixing head that uses the rotor/stator principle. Rotor and stator are fitted with rings of pins which are able to pass the pins on the opposite side when the rotor rotates in the stator. The generated turbulence and shear forces produce a fine dispersion from a pumpable medium and a foam gas, which in this case creates the used foam.

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Hansa Mixer

Read more about aeration in Bronkhorst’s success story on how mass flow meters are important for adding the correct proportion and composition of air bubbles to ice cream.

Ferdinand Luimes
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A Coriolis mass flow meter is known as a very accurate instrument and it has many benefits compared to other measuring devices. However, every measuring principle has its challenges, as also the Coriolis principle. It can be a real challenge using Coriolis instruments in low flow applications in the heavy industry where you may have to deal with all kinds of vibrations. In this blog I would like to share my experiences with you regarding this topic.

The Coriolis principle

Coriolis mass flow meters offer many benefits above other measuring devices. First of all Coriolis flow instruments measure direct mass flow. This is an important feature for the industry as it eliminates inaccuracies caused by the physical properties of the fluid. Besides this benefit, Coriolis instruments are very accurate, have a high repeatability, have no moving mechanical parts and have a high dynamic range, etc.

Read more about the importance of mass flow measurement and the relevance of Coriolis technology in a previous blog.

Do vibrations influence the measuring accuracy of a Coriolis mass flow meter?

In industrial applications, all kinds of vibrations with different amplitudes are very common. A Coriolis meter measures a mass flow using a vibrating sensor tube, which fluctuation gets intentionally out of phase when the fluid flows through. As explained in the video [link] at the end of this article.

This measurement technique is somewhat sensitive to unwanted vibrations with a frequency close to the resonance frequency of the sensor tube (this depends on the sensor tube design, e.g. 360 Hz) or a higher harmonic of this frequency (see picture below).

Image description Coriolis flow meters are only sensitive for the resonance frequency or a higher harmonic of this frequency

The likelihood of the occurrence of these unwanted vibrations is higher in an industrial environment. Coriolis flow meter manufacturers do their utmost to reduce the influence of vibrations on the measured value by use of common technical solutions, such as using:

  • higher driving frequencies
  • dual sensor tubes
  • different sensor shapes
  • mass blocks
  • passive and active vibration compensation

So yes, vibrations can influence the measuring accuracy of your Coriolis flow meter, but only if the vibrations have a frequency close to the resonance frequency. What can you do about this? This depends on the kind of vibration.

What kinds of vibrations do exist?

In an industry zone frequencies can be generated by:

  • environmentally related vibration sources (such as: truck, rail transportation, industry activities)
  • building-based vibration sources (mechanical and electrical installations, like air conditioning)
  • usage-based vibration sources (installed equipment and machines, e.g. pumps, conveyor belts).
  • These vibrations travel through a medium like the floor, in the air, through pipes or the fluid itself. If these vibrations disturb the Coriolis frequency, the measured flow could be incorrect in some extent.

To minimize the effects of vibration it is useful to identify these sources. Sometimes, it is possible to move the flow meter just a little bit, turn it (Coriolis flow meters are in most cases less sensitive to vibrations if the meter is rotated 90 degrees), make use of a big(ger) mass block, use flexible tubes or U-bend metal tubes, or use suspension alternatives.

How could you check the performance of a Coriolis flow meter?

A well performing flow meter and controller will give the best process result. Therefore, it is advisable to test a Coriolis flow meter in your application if you expect heavy industrial vibrations before you trust it to the full extent. Be careful when filtering the measuring signal. In some cases it makes sense (e.g. when a quick response isn’t required), but if you want to test the performance of a flow meter, filtering could blur your judgement.

Image description Coriolis flow meter in action

If in specific circumstances the Coriolis flow meter isn’t performing the way it should, the operator will see a shift in the process output – for example in an application dosing color to a detergent it can result in differences in product color by incorrect dosing and/or unexpected measuring signal behavior. In these cases it makes sense to check the raw measuring signal (without filters!), because it will give you a good insight in the performance of the flow meter. Ask your flow meter manufacturer how to switch off all signal filtering.

Standards regarding vibrations

Remarkably, the influence of external vibrations is not clearly defined in a standard for Coriolis flow meters. Several standards are written about vibrations, but none in respect to measuring accuracy in relation to vibrations. However, two useful standards in relation to vibration are:

  • IEC60068-2, Environmental testing for electronic equipment regarding safety
  • MIL STD 810, Environmental engineering considerations regarding shock, transport and use

As a user of Coriolis flow meters it is important to understand your application, especially about potential external vibration sources. As low flow Coriolis specialist we work together with knowledge partners like the University of Twente and TNO (a Dutch organization for applied scientific research) to get a continually improved understanding of this topic.

With in-house test facilities we are able to do special vibration tests. Together with the experience we gained from customer applications and custom made solutions, we are always aiming for improving our Coriolis flow meters to give our customers the best performance they need.

Watch our video explaining the Coriolis principle:

Read more about the importance of mass flow measurement and the relevance of Coriolis technology in a previous blog.

Check out our success story using Coriolis mass flow controllers for odorization of our natural gas.

Erwin Eekelder
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More and more companies in varying industries are trying to make the transition to low flow solutions. Especially in the chemical industry and food & pharma market the trend is to focus on continuous manufacturing, waste reduction, lower downtime and more flexibility.

In these industries the availability of ultrasonic flow meters for liquids suitable for 1” pipe lines or larger are enormous, but it is much harder finding solutions for smaller line sizes. Conventional ultrasonic flow meters use either the Doppler Effect or Transit Time measurement. These techniques are practically suitable for large bore sizes.

But what about ultrasonic flow meters for flow rates lower than 1500 ml/min or even 200 ml/min?

Due to the complexity of physics and technology there are not many measurement principles present in this particular flow area, especially ultrasonic flow meters. Therefore the big challenge was to find a solution to use ultrasound in tubes with very small diameters. In close collaboration with TNO (Netherlands organization for applied scientific research) Bronkhorst managed to develop an innovative instrument using Ultrasonic Wave Technology. This technology is applied in the new ES-FLOW series for measuring liquid volume flows between 4 to 1500 ml/min independent of liquid density, temperature and viscosity with an accuracy of 1% of rate ± 1 ml/min.

How does Ultrasonic Wave Technology work?

The ES-FLOW ultrasonic flow meter is based on ultrasonic wave technology. Measuring is done in a straight stainless steel tube with an inner diameter of 1.3 mm, without obstructions or dead spaces. At the outer surface of the sensor tube multiple transducer discs are located which create ultrasonic waves by radial oscillation. Every transducer can send and receive, therefore all up- and downstream combinations are recorded and processed. By accurately measuring the time difference between the recordings (nanosecond range) the flow velocity and speed of sound is calculated.

Knowing these parameters and the exact tube cross section, the ES-FLOW ultrasonic flow meter is able to measure liquid volume flows. The distinctive character of this flow meter is that it’s capable to measure the actual speed of sound, meaning that the technology is liquid independent and calibration per fluid is not necessary. Next to that, the speed of sound can be used as an indicator of the type of fluid present in the flow meter.

Image description

Four reasons why to use the ES-FLOW ultrasonic flow meter

1.One sensor for multiple liquids:

Many companies have changing process conditions and make use of various liquids like additives or solvents. As the ES-FLOW technology is fluid independent, recalibration is not needed with liquid changes. Also non-conductive liquids as demi water can be measured.

2.Easy to clean and reduced risk of clogging:

Cleaning processes are often time consuming. Due to the straight sensor tube design with no dead volume, particles have reduced chance of clogging the instrument. Cleaning can be done in a few minutes therefore the amount of down time will be limited.

3.Vibration insensitive:

Ultrasonic measurement is not sensitive for vibrations as it doesn’t rely on frequencies or rotations. It is also irrelevant if the flow is laminar or turbulent.

4.Integrated PID controller and fast response:

The on-board PID controller can be used to drive a control valve or pump, enabling users to establish a complete, compact control loop with fast response time.