Written by Rachel Kohn
Analytical balances are precision instruments providing readouts* to an accuracy of 0.1 milligram and with a linearity** of ± 0.2 milligram. Maintaining this precision is essential to GLP and to be in compliance with regulations guiding the particular industry in which the instruments are used.
For that reason, an analytical balance must be recalibrated at regular intervals and records maintained in further conformance with GLP and ISO standards. Some analytical balances such as the KERN ABT, ABJ and AEJ models available from Tovatech provide automatic internal calibration. Others such as the ALS-A model are externally calibrated at intervals that should be defined in the company’s operations manual.
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Written by Bob Sandor
“Ultrasonic” is generally defined as sound above the range of hearing, which for most people is any sound over 20 kHz or 20,000 cycles per second. The lowest frequency used in a commercial ultrasonic cleaner is typically 25 kHz, which suggests that an ultrasonic cleaner operates silently.
In fact, ultrasonic cleaners do create noise as the frequencies are converted to cavitation action that impacts not only the objects being cleaned but also the cleaning tank itself. As described by OSHA “Most of the audible noise associated with ultrasonic sources, such as ultrasonic welders or ultrasonic cleaners, consists of subharmonics of the machine’s major ultrasonic frequencies.”
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Written by Rachel Kohn
Cavitation action in an ultrasonic cleaner tank results from the violent implosion of millions of microscopic bubbles every second. The implosion creates a temperature of 5000˚C (>9000˚F) and a jet of plasma impacting the objects being cleaned. It is this action that quickly strips away dirt and other contaminants.
Cavitation bubbles are created by ultrasonic transducers that in turn are driven by an ultrasonic generator operating at a set frequency, examples being 40 kHz at a lower level and 130 kHz at an upper level. (Several models are available with selectable dual frequencies.) Lower frequencies create more vigorous cleaning action than higher frequencies. Because of this, they are generally used for removing coarse contaminants. Higher frequencies are used for cleaning products that are more delicate or have highly polished finishes.
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Written by Rachel Kohn
One of the purchasing decisions to be made when considering an ultrasonic cleaner is the frequency at which it operates. Ultrasonic frequency is the term applied to the ultrasonic energy provided by ultrasonic generators and delivered to the transducers affixed to the cleaning tank. It is expressed in kilohertz (kHz).
Ultrasonic cleaners such as those manufactured by Elma and available from Tovatech are available in several frequencies, ranging 25 kHz to 130 kHz. Several units offer a choice between two different frequencies, examples being the Flex and TI-H lines that operate at either 25/45 kHz or 35/130 kHz, and the P line at 37/80 kHz.
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