Sensors and
Charge Amplifiers

For the following applications

Turbines

CP506

General Info

For use in gas turbines, sensors must be designed to be extremely temperature resistant and no "normal" metal alloys or plastics may be used. Consequently, Piezocryst exclusively uses refractory metal alloys, precious metals, sapphire elements and sensing elements made from single crystalline gallium phosphate (GaPO4). Even the cables are exposed to extreme thermal stress, and cooling air temperatures can exceed 500°C, excluding the use of conventional plastic insulated cables. Piezocryst uses what is known as a hardline cable; a metal cable made of extreme temperature resistant nickel-based alloy in which the conductors are embedded in compacted ceramic powder. By implementing these measures, the sensors (including the cable) can be used at a maximum operating temperatures of up to 700°C.

 

Features

  • For use up to 700°C
  • Highest signal quality
  • Designed for minimal vibration and torsion sensitivity
  • Available with acceleration compensation
  • High temperature resistant cable
Expert Info

The insulation resistance of all components plays a critical role for use at temperatures above 400°C, especially for sensing elements. In addition to insulation elements made of sapphire, sensing elements made from GaPO4 are used. This has substantial advantages compared to other piezoelectric materials because at elevated temperatures, the internal resistance is considerably higher. Therefore, the charges created at high temperatures are transported safely to the charge amplifier, a loss of signal due to insufficient insulation is avoided and only pure measurement signals are reproduced. The user can then accurately and reliably measure at lower frequencies.

Transverse GaPO4 sensing elements are used in order to achieve an excellent signal-to-noise ratio. A particular challenge is the application of fatigue endurable electrodes to the thermally anisotropic crystal material, covering the crystal two dimensionally. Piezocryst has developed various high-endurance, high temperature resistant coatings, ranging from precious metals to conducting ceramics just for this purpose, and for which Piezocryst was awarded the research prize for Nano science in the State of Styria (Steiermark), Austria.

In order to accurately measure the impact of acceleration on a turbine, these sensors were designed to be particularly acceleration resistant. Due to their extremely rigid structure, the sensors show almost no acceleration response in radical direction. By reducing relevant mass, low acceleration sensitivity was also achieved in the axial direction. For challenging measurement tasks this can be further reduced through active acceleration compensation. Here, an acceleration sensor is installed inside the pressure sensor housing, and is designed to precisely compensate for the false acceleration signal. In this case, the sensor provides the "pure" pressure signal.

 

Combustion Engines

General Info

To optimize the combustion in an engine, pressure is measured in the cylinder with the highest accuracy. A particular challenge for the pressure sensors is the compensation of thermal shock that goes along with any combustion process. The sensor membranes made from specially selected high-performance alloys are manufactured under extremely tight manufacturing tolerances.

Furthermore, for optimal temperature behavior (no false signals even with massive changes in temperature) the precise matching of the thermal expansion coefficient of isotropic housing materials and anisotropic crystal elements is required. In this case Piezocryst works closely with external materials experts to continually develop up-to-date knowledge and to select the best coupling of materials.

Features

  • Optimized thermal shock behavior
  • Distortion-proof design (double shellTM)
  • Integrated sensor recognition (SAW chip)
  • Reliable measurement campaigns through minimal series deviation
  • Best durability due to high performance materials
Expert Info
GH14D

Under a high temperature gradient, the outstanding material properties of single crystalline GaPO4 sensing elements can reach their full potential (Crystal Technology): There are no false signals caused by temperature changes and the high internal resistance of GaPO4 allows an accurate representation of the pressure curve at highest temperatures. The transverse piezoelectric effect is used to optimize the sensor’s signal-to-noise ratio, optimally adapting the sensitivity of the sensors to the required pressure range.

To achieve highest data quality, it is also necessary that any distortion of the cylinder head does not cause a mechanical disturbance of the sensing elements. For this purpose the so-called Double ShellTM housing is used. It consists of two integrated housing elements, in which the outer element absorbs cylinder head disturbances and the inner element remains force-free. This way the sensing elements only "feel" the purest mechanical pressure signal without error, and the measuring signal is largely free of mechanical disturbances.

This technology is available in different sizes and "packaging" variations for optimal installation under a variety of conditions. The same is for special glow plug or spark plug sensor solutions that are designed for mounting directly in a cooling water jacket. In addition, there are special solutions for thermal high-pressure engines, in which the temperature load is specifically reduced by water-cooling or by front sealing, and thus the life of the sensors is substantially improved even under the harshest conditions.

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High Pressure

GP6

General Info

Due to the low sensitivity of the quartz used, the sensitivity of sensors available on the market is not always adequate. Piezocryst sensors are equipped with GaPO4 crystals. They have all the well-known and reliable characteristics of quartz, but are twice as sensitive. For the sensors with a measuring range of up to 2000 bars, this is a significant performance improvement over the current state of ballistic measurement technology and a significant improvement in data quality. For sensors with a range of 6000 to 8000 bars, this is expressed in a significantly improved signal-to-noise ratio.

Features

  • Highest sensitivity
  • Excellent signal-to-noise ratio
  • Minimum hysteresis through extremely rigid construction
  • Distortion-proof design (Double Shell™)
Expert Info

Under extreme pressure an extremely rigid sensor construction is required to prevent any disturbance due to hysteresis and the associated restoring forces. Piezocryst high-pressure sensors are based on special load-stable crystals cut in longitudinal effect with the lowest dependency of the sensor signal on pressure range. These sensors have a special Double Shell™ construction, which frees the sensor from disturbances within the installation environment. In addition, due to the extreme need for compressive strength and thermal shock independence, the membrane must be made of high-performance alloys with very narrow tolerances to ensure durability and signal quality. Another important factor in performance is the seal. Piezocryst has developed a special sealing system that will stay safely sealed under high-pressure gradients and mechanical shock, while distributing the resulting forces so that the Double Shell™ housing is not subject to interference. This gives measurement results in a new kind of data quality.

The product range includes pressure sensors for measuring ranges up to 2000, 6000 and 8000 bars. All of these sensors have an M10 thread, so that measurements of different pressure ranges within one bore are possible.

 

Mobile Indicator Systems

General Info

By mounting on the indicator cock of a large engine, indicator sensors may be exposed to enormous amounts of thermal stress; as they are in contact with the hot combustion gases, but have no contact with the engine’s water-cooling system. To meet these requirements, Piezocryst sensors are fitted with temperature-stable, single-crystalline GaPO4 measuring elements. These sensor elements have an extremely high internal resistance, allowing the highest signal quality even at high temperatures and low speeds, conditions under which other piezoelectric materials already show hardly compensated error images. Piezocryst sensors are equipped with a heat sink, which keeps the charge amplifier’s electrical system from overheating. This makes it possible, for example, to keep the sensors on the indicator cock longer and to directly track the results of manual adjustments to the motor.

Features

  • Highest signal quality, even at low engine speeds
  • Overheat resistant design
  • Additional safety with Leak ProofTM
  • Extremely robust design
Expert Info
GO51S

The charge amplifier is also specially adapted to the requirements of the mobile indication analysis. It uses a specific logic, which allows ultra-fast recognition of individual combustion cycles and thus significantly minimizes the required measurement time.

Due to the variety of assembly and disassembly operations, the sensors must be mechanically robust. They have a massive clamping nut fit for a Thomson adapter, and the delicate membrane of the indicator sensors is set back to prevent mechanical damage. If they should still get damaged, the sensors are also equipped with the patented Leak ProofTM safety design that prevents the operator from being exposed to hot combustion gases. In addition, the sensors are equipped with a high quality reinforced metal cable, and a thermal decoupled handgrip for easy handling. 

Large Engines

GO31J

General Info

The special challenge in monitoring and controlling large engines is to ensure excellent data quality over a lifetime of several years under the demanding conditions of a large engine. The sensors are not only exposed to high-pressure surges, but also simultaneously experience tremendous stress due to thermal shock and high acceleration. The piezo-measuring technique is particularly advantageous for these extreme requirements since it essentially measures almost displacement free, in contrast to other sensor technology such as strain gauge (DMS). Thus, the maximum range is within few micrometers or significantly less as a result of the extremely rigid GaPO4 crystals - whereas DMS requires a relatively soft deformation body often requiring 10 times the distance covered during operation. These minimal distortions under such harsh environmental conditions made possible by piezoelectric measurement technology, offer minimal material fatigue and therefore a significant increase in service life and reliability.

Features

  • Extreme longevity
  • Highest signal quality
  • Leak ProofTM Safety Design
  • Accurate signal reproduction through high quality charge amplifier
Expert Info

Large engine sensors are equipped with a variety of different technology and sophisticated design details, many of which are patented or patent pending. In addition to the tried and tested Double Shell™ construction, which compensates for disturbances in the cylinder head, or the internal tension element the extremely robust and thermally stable GaPO4 sensing elements are used. Alternatives to piezoelectric materials have significantly reduced internal resistance compared to GaPO4. If such crystal elements are used in sensors, many charges are "lost" due to low insulation resistance, and the measuring signals from such sensors are systematically subject to speed-dependent distortion. In contrast, the extremely high insulation resistance of GaPO4 crystal elements is also given at high temperatures, even allowing correct and undistorted reproduction of the pressure signal in low speed 2-stroke engines.

In addition, Piezocryst sensors are equipped with a unique Leak ProofTM safety design. This feature is designed so that even in the unlikely event of a membrane rupture, sensor parts take on the function of a safety valve and seal the cylinder from the environment. Under all circumstances, the leakage of hot combustion gases is prevented, the operator and the engine are protected, and unscheduled engine stops are avoided.

The sensors are equipped with a high quality charge amplifier. This charge amplifier "recognizes" the pressure signal and automatically compensates for any drift. This sophisticated technology makes it possible to avoid the weaknesses of simple charge amplifiers equipped only with feedback resistors and to accurately reproduce signals.

Materials Technology at Piezocryst

You can only use materials efficiently and safely if you know them well.
Noble metals, single-crystalline and other high-performance materials: Piezocryst knows and understands the specific characteristics for the best combination.

Plastic Injection Molding

General Info

In plastic injection molding, temperatures with which melted mass is forced into tools can reach up to 400°C and pressure can exceed 2000 bars. Cavity pressure sensors must be able to withstand these conditions, and very small sensors are required for modern multi-cavity tools. In order to optimally meet various installation situations, the sensors are available in plug-in and screw-type models, as well as different sizes. Regardless of design, all the sensors are equipped with a detachable cable and can be easily used even in the event of cable damage.

Features

  • Precise measurement, even with miniature sensors
  • Low variability
  • Automatic sensitivity detection
Expert Info
6006BB

Piezocryst sensors have a precision-machined piston, which transfers the melt pressure onto the crystal elements. This piston is enclosed in a protective sleeve, which largely compensates for bore tolerances in the tool. This technology is also protected by our cooperation partner Priamus System Technologies, as is the automatic sensitivity detection. Here the sensitivity of each sensor is determined and classified by a precision resistor; meaning the sensors have a sensitivity detection that is inextricably connected to the sensor, and in the case of a cable swap, also guarantees the correct read out of individual sensitivity.

Industrial Process Control

Low Profile Force Sensor

General Info

Reproducibility of the sensor signal and sensor life are both critical to the use of sensors in industrial process control. Ideally, the sensors have a product life that corresponds to the entire operation of the machine or at least a major inspection interval. The sensors should never have to be changed during normal operation. To reflect these needs, Piezocryst sensors are designed so that the shunting effect in the sensors is largely minimized, meaning that nearly the entire force to be measured flows through the piezo elements. Undesirable side effects such as hysteresis or creepage are minimized, as sensor properties depend largely on the piezoelectric crystal elements. By skillfully selecting the piezoelectric materials and sensing element geometry, it is possible to achieve nearly perfect measurement properties.

Features

  • Highest signal quality
  • Patented design minimizes unwanted interference
  • Highest linearity and extreme overload protection
  • Superior durability
Expert Info

In addition to specific sensing elements, Piezocryst uses a patented semi-shell structure for force-sensor washers, replacing the conventional asymmetrical with a symmetrical structure. As a result, the sensors are less sensitive to adverse influences, and extremely flat sensors can be realized with an enormous stability.

Due to the extreme stiffness of the piezoelectric elements, distortions are minimal under force. Typically distortions happen in the µm range and are significantly lower than alternative methods of measurement. In addition, crucial force-displacement information for many applications is not affected by the use of piezoelectric sensors. Minimal distortion ultimately means that possible wear and tear is reduced to a minimum resulting in a long product life. The results of combining sophisticated design with advanced manufacturing technology are extremely linear sensors with enormous overload capabilities.

Thus, sensors with a maximum load of 50,000 N are able to reliably process forces in the mN range and measurements of the lowest strength are easily possible even with high mechanical preloads.

Charge Amplifier

General Info

Piezocryst uses its own charge amplifier technology, which can be customized depending on application and customer need. The standard amplifiers available range from cost-effective solutions with fixed input ranges to high-quality multifunction charge amplifiers, which have several automatically switchable gain ranges. The amplifiers are free to configure and have analog and Ethernet output. The analog outlets have a bandwidth of 30 kHz, so that fast processes can be clearly displayed in high quality. The digital outlets have a bandwidth of 1 kHz, so that a continuous data streaming is ensured, for example for monitoring or control purposes.

Features

  • Highest linearity through automatically switchable gain ranges
  • Ethernet for data streaming
  • Automatic signal detection
Expert Info

These amplifiers are increasingly being used in industrial process control and enable Ethernet output monitoring of production machines (Industrial process control). In addition, amplifiers are available that automatically synchronize to specific waveforms and have automatic drift compensation. Such charge amplifiers, for example, are ideally suited for monitoring and controlling combustion in engines. (Large Engines)