Meaning
Piezoelectric sensor instrumentation relies on charge amplifiers to convert electrostatic signals from cavity pressure transducers into proportional voltages. When the input charge exceeds the design range of the measurement circuit, charge amplifier saturation occurs, driving the output voltage to its upper limit. This condition prevents the system from recording further pressure increases, which renders the peak pressure reading inaccurate during the injection moulding cycle.
Voltage Limit
High cavity pressures generate large electrostatic charges that can quickly overwhelm the measurement range of the system. If the feedback capacitor in the amplifier is sized too small, the accumulation of charge forces the operational amplifier to its maximum rail voltage. The signal remains clipped at this ceiling until the input charge decreases.
Signal Distortion
An over-range condition truncates the pressure curve during the holding phase of the moulding process. This truncation hides critical process variations such as peak pressure spikes, making it impossible to detect flashes or short shots through cavity pressure monitoring.
Recovery Duration
Resetting the circuit requires a finite period for the feedback capacitor to discharge once the cavity pressure drops. This delay can extend into the next moulding cycle if the cycle times are very short, resulting in consecutive corrupt data sets.
