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We have developed these recommendations to improve measurements, and to help extend the life of our hydrophones. You may find this helpful for other hydrophones too.
Never physically touch the sensing point of the hydrophone. The small sensing area is coated with thin layers of metal and/or polymers that can be damaged, leading to degradation in performance. Dropping or bumping the tip of a needle hydrophone on a hard surface will generally result in some damage to the device. Even using a soft brush to remove bubbles may be risky as a slight misplacement can bring the hard part of the brush against the hydrophone. Instead, we recommend using jet of water from a squeeze bulb or a syringe, or a low pressure stream of clean air or other gas to remove liquids or particles.
Do not insert the tip of needle hydrophones into a test fixture. Doing so may cause inadvertent contact between the tip and the fixture, and is one of the most common ways of destroying hydrophones. We have side mount clamps available that avoid this risk.
Connect the power supply into the DC block as the last step in any hydrophone connection sequence. If a connection is made under load, a high shorting current arises and can cause damage. More specifically, it is possible in some circumstances for the center pin of the mating SMA (male) of a preamp to contact both the center receptacle and ground of this connector if the misalignment between the hydrophone and preamp is severe during the connection.
Limit the amount of time that the hydrophone is immersed in liquid. During a break or at the end of a test session, it is best to remove the hydrophone from the liquid (water or other). This will help extend the life of the hydrophone.
Use high resistivity water with membrane hydrophones. We recommend a minimum of 200 kohm-cm because conducting water becomes a capacitive shunt across the device, which affects low frequency readings. Fresh deionized or distilled water is recommended because it usually has a high resistivity of 1 Mohm-cm or more. Routine checks of conductivity will ensure accuracy in the measurements.
Use clean de-ionized and degassed water for high intensity measurements. Deionized water is best to avoid electrical coupling in strong conducting fields. Also degassed, clean water improves the accuracy of the readings by avoiding bubbles or other scatterers. We offer water treatment devices for de-ionizing and degassing water to meet your needs.
Use only the supplied box to store your hydrophone. Our hydrophone boxes are designed to ensure that the sensing area is safe from all contact while in storage, and to minimize the risk of mishandling or dropping the hydrophone.