How can I make ultrasonic intensity measurements?
A simple guide can be found here "Simple Guide to making ultrasonic intensity measurements or if you are in the UK you might be interested in our "Hydrophone users course" in the education section
Can I use my hydrophone in liquids other than water?
Hydrophones can be used in castor oil or mineral oil. The hydrophone is constructed from PVDF which although resilient can be damaged by some chemicals. Consult our web page Properties of poled piezo-electric PVDF film.
Do I have to soak the hydrophone?
All hydrophones should be soaked before use. Although most hydrophones stabilise after about 10 minutes, our recommendation is to soak for 1 hour so that the output stabilises before measurements are taken, .
How long can I leave the hydrophone in water?
Hydrophones should be removed from the water as soon as possible and we advise that if they are left immersed longer than 24 hours they are removed as soon as possible and dried out.
How do I dry the hydrophone?
If possible rinse the hydrophone tip in distilled water at the end of a measurement session and leave to air dry or place in a warm oven at no more than 50 °C. Do not touch the hydrophone tip.
How do I clean the calcium deposits from the hydrophone?
Immerse the hydrophone tip in lemon juice and then rinse in distilled or running water.
Do I have to terminate the hydrophone output in 50 ohms?
The input and output from your measurement equipment should be terminated with 50 Ohms.
The preamplifier has 8dB gain-what does this mean?
It doesn't matter whether you measure it as a power or voltage ratio - you'll get the same dB result.
Can I use batteries to provide power to the DCC?
Three 9v batteries in series will give enough voltage but they will not last very long and may cause changes in the measured signal. All DC Couplers supplied after March 2008 are supplied with a small desktop power supply suitable for use with the hydrophone system. Contact us if you wish to purcahse a PSU for use with older ssytems.
Does the DC Coupler affect the gain?
No - it simply powers the preamp and removes the dc component from the returned signal.
Is there any way to attach a measurement device to the DC coupler to measure the amount of gain?
Yes, you can feed a test signal in and measure the response. You will need to use a 50 Ohm terminator at the input if you use a 50 Ohm signal source. You will also need to use 50 Ohm input on your oscilloscope.
Is the calibration sensitivity data an RMS or peak value?
The sensitivity is simply a conversion factor between pressure and voltage. If you measure peak-to-peak voltage and apply the conversion factor, you will measure peak-to-peak pressure. If you measure rms voltage and apply the conversion factor, you will measure rms pressure. The same will be true for peak positive, peak negative, etc.