The stable output of ultrasonic cleaning results from the control of several variables. Understanding and controlling these variables is fundamental to maintaining and improving your ultrasonic cleaning process.
6 variables affect cleaning performance:
- Power Amplitude ( results in cleaning force per unit area, Pascals)
- Tank Size and Geometry
- Location of parts
Out of these 6 variables, power amplitude is the one most likely to fault your cleaning process. The power amplitude decays due to aging transducers. For tanks with variable power control, the cleaning force/area can be adjusted in order to maintain the same level of performance, but up to a limit. As the power degrades, the cleaning force drops proportionately. The Sonic Meter is specifically designed to quantify changes in the power amplitude.
Frequency is fixed. Tanks can have multiple transducers with different frequencies. The discrete frequencies can be “swept” from one frequency to another, but frequency is not incrementally variable. This is not a variable that decays. It’s inherent to the piezo transducers.
Chemistry and Temperature
The chemistry and temperature both play key roles in cleaning force performance. Both optimum temperature and chemistry promote efficient cavitation and distribution of cavitation pressure. Refer to your tank manufacturer for process guidelines when selecting temperature settings, degas time and solvent solutions.
Tank Size and Geometry
Tank size and location of transducers to the exterior of the tank play important roles in the pressure distribution of cavitation throughout the tank. In large tanks, sparsely populated transducers can have a significantly varied pressure map with large volumes of low pressure. The tank’s geometry can have a significant impact on the distribution of cavitational forces throughout the fluid volume. Filters, hangers, racks, non-symmetric tank volumes, voids and protrusions can break up the uniform distribution of ultrasonic energy forces throughout the tank’s volume.
Location of Parts
Using the Sonic Meter to map the tank’s pressure profile is extremely powerful not only in monitoring performance, but also in determining locations and settings for optimal pressure amplitude. With the tank mapped, parts can be placed in the locations where pressure energy distribution is optimized.
Over time the tank’s ultrasonic transducer and the mechanical coupling to the tank degrade, which can result in significant cavitation pressure loss. For tanks in continuous use, this change can be noticeable in as little as 6 months for a new tank. Scheduled mapping cycles to measure tank degradation is critical for tracking transducer decay and changes in the pressure map. Understanding the lower threshold of your process is accomplished through controlled measurement of pressure density via tank mapping and close inspection of the cleaned components.
How the Sonic Meter works
The power amplitude is quantified by measuring the tank’s fluid pressure at a number of predefined points. The Sonic Meter is the only meter on the market with ability to measure and calibrate the tank’s internal cleaning force. The Sonic Meter’s slender probe can pinpoint areas of optimum output or detect transducer degradation after mapping the pressure profile in SI units (Pascals). Employed in the meter’s construction are state of the art electronics, algorithms and hermetically sealed sensing technology. The output of the meter is based on wide-band pressure sensing technology and high precision analog to digital filtering with constant reference signal monitoring. The piezo sensor is contained in a hermetically sealed and hardened stainless housing. The sensor’s sensitivity has been specifically tuned to work with cleaning tanks operating in a frequency bandwidth of a few thousand Hertz to 500 kHz. The bandwidth and sensitivity of our meter was designed to work with the most common cleaners on the market from tank cleaners to cell disruptors-processors.
The Sonic Meter provides two options for taking measurements:
- Real time reading (updates every 50msec), this option gives the instantaneous pressure output of the tank at a given position.
- Averaged reading, sample 1-40 readings at intervals of 10msec to 100sec. Ten samples at 1-sec intervals works for most applications. For both options there are user defined high/low limits. A visual alarm is displayed when a reading is out of range. This alarm will indicate if the reading is above or below the user-specified limits.