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Ultrasonics Applications and Solutions for Industry and Research



Capacitive Transducers Page

VN Instruments has developed its own line of transducers.  These devices are well suited to industrial and research environments.  They offer superior bandwidth,  very good sensitivity, and stability over time.  The devices function well under a range of conditions and can be cleaned with conventional solvents.  Our capacitive transducers are suitable for all air coupled applications.

Piezoelectric transducers often add spurious features to an image that are due to the internal construction of the transducer.  Capacitive transducers have a high dynamic range and clean linear signal that make analysis of the ultrasonic data very simple.

We offer devices with bandwidths as low as 60% and as high as 200%.  Our standard devices operate with center frequencies of around 60kHz, 120kHz, 350kHz and 1MHz.  A broad bandwidth transducer is especially useful in analyzing mechanic properties of materials.  We can also make transducers to customer specifications.  Contact our technical sales department for details. 

Air coupled piezoelectric transducers tend to operate in relatively narrow bandwidths.  It's often necessary to use many different sets of transducers when studying a new material since each transducer covers a small frequency range.  With a broadband device changing frequency ranges is done in software. 

Ultrasonic spectroscopy is the use of broad spectrum signals to measure the change in signal strength as a function of frequency.  These types of measurements can reveal information about cell size and other related internal structures.  A broad bandwidth transducer without unwanted internal features is an advantage to this type of measurement.

Our line of capacitive transducers requires a stable and quiet high voltage bias source.  VN's Remote Modules provide the necessary bias voltage under full software control of the SIA-7.  The Remote Modules make the capacitive and piezoelectric transducers interchangeable in many applications.

  • CAP1 – 60kHz: These are our lowest frequency devices.  They have high gain and an effective bandwidth of about 35kHz.  They are well suited to bulk materials including concrete and thick wood samples.
  • CAP2 – 120kHz: CAP2 transducers offer surprising signal strength with about 80kHz of usable bandwidths.  These devices are often used for thick and highly attenuative samples.
  • CAP3 – 300kHz: These are the most general purpose devices.  They are well suited to a wide range of applications.  These have a nominal bandwidth of about 300kHz and very good sensitivity. 
  • CAP5 – 150kHz to 1.3MHz: CAP5 transducers provide an enormous bandwidth.  The frequency range is so large that we don’t refer to a center frequency because the devices can be used across the entire spectrum.  These are well suited to spectroscopy and thin materials.  The overall gain is lower than other transducers so measurement speeds tend to be lower.
  • Focusing Options: Any of our transducers can be mated with a reflective element to produce almost any focus required.  Please contact our technical sales department for details.


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Copyright © 2007 VN Instruments Ltd
Last modified: April 02, 2007