Understanding Transducer Specifications - 2 Pages

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Understanding Transducer Specifications

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Understanding Transducer Specifications RMS Power vs Peak-To-Peak Power All Airmar transducers are measured in RMS power as opposed to peak-to-peak power ratings. Peak-To-Peak power ratings are eight times higher than RMS power, which can trick the consumer into thinking their echosounder and transducer are more powerful than they really are. For example, if transducer manufacturer L advertises 4,000 Watts peak-to-peak power, this is only 500 Watts RMS power. See the chart below for typical Airmar transducers and their power ratings in both RMS and Peak-To-Peak. Airmar Transducers with a “Q” of less than 8 are considered “Broadband”. Airmar’s definition of “Broadband” is a wide frequency band in which the transducer can operate between a high and a low-frequency value—for example 33 kHz to 60 kHz. Broadband performance results in faster rise and fall times which generate a distinctly crisp acoustic pulse. A Transducer’s quality factor, “Q” describes the amount of ringing the ceramic element or elements undergo when power is applied to the transducer. Think of a church bell analogy—as the bell is struck it vibrates rapidly and then the vibration will gradually stop. Most competitor’s recreational transducers have an average Q between 25 and 35. Airmar Q values range from 1 to 30, depending on models. The lower the “Q” number the less ringing in the transducer and the better the performance. Less ringing greatly improves individual fish separation along with bottom imaging in rapidly changing water depths such as ledges and offshore canyons. Peak-To-Peak Power Airmar measures transducer beamwidth at -3 dB. Other transducer manufacturers measure their beams at -6 dB and -10 dB, stating the beam is wider than it really is at -3 dB. For example, the image below shows a beamwidth of 20° at -3 dB (see the red line). If the same transducer is measured at -6 dB, the beamwidth increases to 30° (see the green line). Because broadband transducers have a bandwidth that covers a continuous frequency spectrum, future fishfinders can be made ‘tunable’ so fishermen can ‘dial in’ the best frequency for the target fish species or conditions. For example, Airmar’s 2 kW R209 can operate anywhere between 130 kHz and 210 kHz. This allows a range of custom performance possibilities. Tuning a higher frequency will increase the target resolution of small fish, and the narrower beam will reduce side lobes in areas with fast-changing water depths. Lowering the frequency results in a wider beam and better deep-water performance. In summary, Broadband Technology has the potential to change the way fishfinders are designed and unlock new levels of fishfinder performance in the future. Broadband Transducer Imaging 50 kHz Non-Broadband Transducer Imaging Transmitting Voltage Response Transmitting Voltage Response (TVR) is computed using Receiving Voltage Response and Impedance. The unit of measure for TVR is dB relative to 1 micropascal per volt at a distance of 1 meter (3’). Receiving Voltage Response Receiving Voltage Response (RVR) is measured typically by applying 200 V peak-to-peak to the transducer under test, pointing it at a nearly perfect reflector, and measuring the echo amplitude as a function of frequency. The unit of measure is dB relative to 1 Volt per micropascal. Figure of Merit This graph is a summation of TVR and RVR and provides a measure of two-way performance. A transducer whose figure of merit response has a wide bandwidth is generally preferred over a transducer with a narrow bandwidth. The former usually rings less and offers most consistent performance over the transducer’s range of frequency tolerance. 180 This Broadband transducer has a flat response and can run across the entire frequency range. With this technology, transducer ringing is diminished and the Q is usually lower than 8. The crisp pulses allow for superior detection of tightly spaced fish and also fish suspended very close to the sea floor. When used for navigation purposes, broadband transducers also do a better job of imaging the bottom at all depths, especially very shallow-water. This Non-Broadband transducer peaks its performance at 200 kHz and drops off sharply at frequencies before and after.

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Understanding Transducer Specifications What Goes into the Making of a Transducer? A good fishfinder depends on an efficient transducer to send and receive signals. The transducer is the heart of an echosounder system. It is the device that changes electrical pulses into sound waves or acoustic energy and back again. In other words, it is the device that sends out the sound waves and then receives the echoes, so the echosounder can interpret or “detect” what is below the surface of the water. The main component of a depth transducer is the piezoceramic element. It is the part that converts...

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