HTM0105 states that you should test your ultrasonic cleaner quarterly with test foil to validate the operation of the transducers - tests the frequency of the vibration. Walker Electronics advises testing of multi-transducer tanks with this foil. This foil is 0.018mm thick, meaning it is the correct gauge for HTM0105. This foil has all the correct measurements, and longevity, for multiple tests of your ultrasonic cleaner.
Walker Electronics Ltd have this to say on the matter:
On a single transducer tank it is Walker Electronics Ltd opinion that either a load test or foil ablation test alone will determine the efficiency of cleaning of the ultrasonic cleaner. If there were a fault that leads to a failure of the Protein test this fault would also have led to a failure of the foil ablation test. Conversely, if there were a fault that leads to a failure of the foil ablation test this fault would also have led to a failure of the protein residue test.
Walker Electronics Ltd are therefore of the opinion that the foil ablation test provides little or no benefit in assessing the efficacy of the ultrasonic cleaner WITH A SINGLE TRANSDUCER and therefore this test can be omitted from the service schedule of its model QC and Q105 units.
Weekly, preferably each day if possible.