Amplification
for hot
applications
Piezo sensors with integrated amplifier electronics cannot be used in high-temperature applications, as these cannot withstand the temperatures. Here, external charge amplifiers are used which convert the charge signal outside the high temperature zone into a voltage or current signal and can thus also transmit it over longer distances.
The IFTA ChargeAmplifier is an Ex nA (ATEX Zone 2) certified, differential in-line charge amplifier that is specially tailored to the requirements of high-temperature sensors.
The IFTA ChargeAmplifier offers Ex nA (ATEX Zone 2) certification for explosion protection, is supplied via IEPE and is perfectly suited for piezo sensors in high-temperature environments.
The IFTA ChargeAmplifier can be integrated between sensors and measurement devices without the need for an external power supply because it receives its power from an IEPE. This simplifies the measurement chain and makes the charge amplifier universally compatible and inherently short-circuit-proof.
The IFTA ChargeAmplifier is a differential charge amplifier that ensures optimal protection against common-mode noise such as mains hum, thus optimizing signal quality. A version with optimized CMRR is available for single-ended sensors.
In industrial environments, it is important to pay attention to the electromagnetic compatibility of measurement equipment. This aspect was particularly considered during the development of the IFTA ChargeAmplifier and was the subject of numerous tests in the EMC laboratory and in the field.
A version with Ex nA (ATEX Zone 2) certification is available for use in hazardous environments. With this option, the IFTA ChargeAmplifier can be located in the ATEX Zone 2 and the measurement system can be located outside of that zone.
Depending on the sensor, the appropriate optimal amplification can be selected. In addition to the standard amplifications, individual adaptations can also be realized cost-effectively thanks to the modular amplifier concept.
In high-end A/D converters, such as those used in the IFTA AD4 line, for example, 24-bit precision is now available. To make the most of this precision, IFTA ChargeAmplifier offers particularly low-noise amplification. At 1 kHz, the SNR is 116 dB.
The IFTA ChargeAmplifier is used to convert dynamic charge signals into a voltage signal, which can be transmitted over longer distances to the measurement system.
| Number of channels : | 1 |
| Frequency range: | 3 ... 20000 Hz |
| Weight: | 175 g without ATEX housing |
| Input impedance: | 1 MΩ |
| Amplification: | 5, 10, 25, 50, 100 or 250 mV/pC |
| Signal-to-noise ratio: | up to 116 dB |
| Coupling: | AC-coupling |
| Operating point: | 12 VDC |
| Output signal: | ±5 VAC |
| IEPE supply: | 8 … 12 mA |
Testing
Service
Forschung
Sensor crackers ("popcorn effect") pose a particular challenge for the charge amplification of high-temperature sensors. They occur when such a sensor is heated so quickly that thermal stress builds up in the piezo element. If the material suddenly relaxes, large amounts of charge are suddenly released. In simple charge amplifiers, the so-called pyroelectric effect can also overdrive the electronics for seconds and thus effectively blind it.
To meet this challenge, special measures have been taken to minimize the impact of this effect with the IFTA ChargeAmplifier. In addition, the software recognizes typical error patterns and can take this information into account during analysis, thus avoiding incorrect control actions.
The result is a charge amplification with maximum availability and reliability.
A typical application of such a measurement chain is the measurement of pressure in combustion chambers of stationary gas turbines in order to identify thermoacoustic combustion instabilities. For this purpose, the voltage signal that the charge amplifier generates is sampled by an analog input module (e.g. AD4 IEPE). The IFTA ArgusOMDS system performs special analyses of the frequency and time domains and, via a communication interface with the gas turbine controller, protects the machine against damage caused by combustion oscillations. Effective compensation for sensor "shots" is particularly important with such applications, so that costly unnecessary machine shutdowns can be avoided. In combination with the IFTA ArgusOMDS, the charge amplifier with piezoelectric high-temperature sensors is used on stationary gas turbines to protect against thermoacoustic vibrations in combustion chambers.
When the distance to the measurement system to be bridged is just a few meters, the input module IFTA AD4Pro can be used. Each input of the module has its own integrated complete charge amplifier that can optionally be switched on.
Due to the charge signals short transmission paths, this design enables optimal signal quality and flexibility. IFTA AD4Pro is also suitable for mobile applications, as additional electronics are eliminated. The amplification is configured via software and stored along with all of the measuring system's other configuration data. Especially with larger test setups, this has the decisive advantage that changes logged for past configurations can be easily restored. Thus, sources of error will be avoided and set-up is more flexible.
Fast & intuitive online/offline analysis software for efficient visualization.
Do you have any questions about vibration measurement? Do you need assistance with the interpretation of measurement data? We are pleased to support you. Get in touch with us or send us a request.
