The main precautions when using ultrasonic transducers
When using an ultrasonic transducer, the main consideration is first the matching with the input and output ends, and then the size of the mechanical installation and matching. The frequency of the transducer is relatively intuitive. Frequency refers to the frequency measured by the transmission line method using a frequency (function) generator, millivoltmeter, oscilloscope, etc., or using similar instruments (such as a network impedance analyzer). Usually called the small signal frequency. The corresponding is the computer frequency, that is, the actual operating frequency measured when the customer connects the transducer to the chassis through a cable and powers it on under no load or load. Because the customer's matching circuit is different, the frequency of the same transducer in different driving power sources (electric boxes) is also different, and this frequency cannot be used as the basis for exchange discussions.
Let the transducer, the driving power supply and the mold cooperate well to form a complete ultrasonic equipment, referred to as matching. Since the impact of matching on the performance of the entire machine is decisive, no matter how important the importance of matching is emphasized, it cannot be overstated. The main consideration for matching is the capacitance of the transducer, followed by the frequency of the transducer.
The matching between the transducer and the driving power supply mainly includes impedance matching, frequency matching, power matching and capacitive reactance matching. The most important are capacitive reactance and frequency. As mentioned earlier, since the ceramic plate is an insulator, you can almost understand that the transducer is not energized, it is equivalent to a capacitor. In order to make the transducer work normally, in fact, a high AC voltage is applied to it through the drive circuit to charge and discharge the capacitance of the transducer. The piezoelectric ceramic sheet undergoes simultaneous expansion and contraction under the action of an alternating electric field, thereby forming the longitudinal vibration of the entire transducer, thereby driving the vibration of the horn and the mold. Therefore, if the matching of the capacitor is not good, the lighter sensor is the weaker transducer and the welding is not strong. The heavier sensor will heat up severely, burning the electrode of the power supply and the high-power tube. Our transducer products come with a product performance parameter table, which shows the capacitance and frequency of each transducer. The driving power supply should adjust the high voltage transformer according to the capacitance of the transducer, matching the parameters of the capacitor plate, the peak coil and the frequency modulation coil. Due to the sensitivity of inductance and capacitance, power amplifier boards, chokes and other peripheral circuits will also affect matching. Moreover, as the work progresses, the temperature of the transducer will increase, resulting in an increase in capacitance, and the change may exceed 50%. If the capacitance cannot be matched effectively, it will cause a large current and voltage phase difference in the loop, the power factor is very low, and the virtual work is very high. Look at the large current, but the transducer is weak and easy to heat, and the power device of the power supply is also easy to heat and damage. Usually, it may be due to a broken or burnt transducer electrode (ear).