TIPS FOR USING OHMIC’S ULTRASOUND POWER METERS
TIP #1 This is the most important tip. Read the Manual.
Why: Details of assembly, storage and usage for each unit is given. Current manuals are available on line at www.ohmicinstruments.com . Most older manuals are also available by calling technical support at 410-820-5111.
TIP #2 Assemble the ultrasound Power Meter (UPM) according to the instructions given. Why: Ohmic’s UPM’s are constantly updated. Each UPM comes with specific instruction, for use, located on the tank. Older units have lockout mechanisms, current ones do not. Depending on the model used the order of these instructions will change.
TIP #3 Use degassed water for best results. Why: Degassed water has an oxygen content of less than 5 ppm, this is recommended for testing. Tap water oxygen content is 20 to 40 ppm. Non-saline distilled water used for irrigation has an oxygen content of 4 ppm and may also be used.
TIP #4 For uncritical testing tap water that is not aerated may be used. Why: The water will indicate when out gassing occurs by forming bubbles. This can occur during extended or higher power testing. The UPMs reading will also slowly fall indicating out gassing. The water should be changed at this time.
Tip #5 The UPM and water medium should be allowed to acclimate, (come to near room temperature preferably around 70 Deg. F.). Why: The electronics work better at room temperature. The readings are affected by temperature which causes changes in the pressure of the water and the sound velocity.
Tip #6 The effects of temperature can be canceled over a temperature range of 5 to 45 Deg. C. by adding 18% ethyl alcohol by volume to the tank’s test water.
Why: Water has a positive temperature coefficient under 74 Deg. C. and ethyl alcohol has a negative temperature coefficient.
Tip #7 Positioning the cone assembly parallel to the bottom of the tank and installing the transducer of the unit under test directly over the cone’s point gives the best readings.
Why: Proper alignment reduces reflections.
Tip #8 Controlling the environment: vibrations, magnetic fields, HVAC vents, foot traffic, using a stable surface, will give faster more accurate readings.
Why: On the UPM-DT-1 the minimum display reading of 0.001 watts is 0.00006826 grams. This is a minuscule weight. As an example, waving your hand over the tank of the UPM-DT-1 can cause a fluctuation as high as 0.030 watts or more.