I. Preparation and Status Confirmation Before Calibration
Power on the hot runner signal generator and allow it to warm up for at least 30 minutes to allow the internal crystal oscillator and analog circuitry to reach thermal stability, eliminating initial deviations caused by temperature drift.
Enter the device's "System Settings" menu and perform a self-test to confirm that all channels have no hardware errors and the device is functioning normally.
Disable all AM, FM, PM, and other modulation functions, and uniformly select a standard sine wave/DC signal as the output waveform to avoid additional signal interference during the calibration process.
Connect a process signal calibrator with an accuracy class ≥ ±0.01%, a high-precision frequency counter, and a multi-channel oscilloscope with a bandwidth ≥ 100MHz, and complete the warm-up of the reference equipment.
II. Frequency Reference Recalibration
Set the signal generator output frequency to a typical value of 10MHz and use a high-precision frequency counter to measure the actual output frequency.
If the measured value deviation exceeds ±1ppm, enter the "Frequency Calibration" menu and adjust the "Frequency Correction Factor" until the deviation is zero.
The calibration process covers the commonly used 10kHz, 1MHz, 10MHz, and 100MHz frequency bands for hot runner calibration to ensure clock reference accuracy meets standards.
III. Output Amplitude Recalibration: Set the output amplitude to 1Vpp (peak-to-peak) and measure the actual output amplitude using an oscilloscope or high-precision multimeter.
If the deviation exceeds ±1%, adjust the "Gain Correction Value" through the "Amplitude Calibration" menu to eliminate amplitude output error.
The calibration covers the commonly used 10mVpp, 100mVpp, 10Vpp, and 20Vpp amplitude ranges for hot runner calibration. For high amplitude calibration, enable the oscilloscope's high-impedance input mode (≥1MΩ) to avoid load effects introducing deviations.
IV. Waveform Distortion Recalibration: Output a 1kHz sine wave and use the oscilloscope's THD (Total Harmonic Distortion) measurement function to check the waveform distortion.
If the THD exceeds the specification of -60dBc, adjust the signal generator's "Waveform Optimization" parameters, such as filter bandwidth and waveform smoothing coefficient, to reduce waveform distortion.
To address waveform distortion caused by capacitive loads, the "pre-distortion compensation" function is activated to reverse-correct the output waveform, ensuring that the waveform accuracy meets standards under load.
V. Specific Recalibration of Thermal Signals
Thermocouple Signal Calibration: The signal generator is set to output millivolt analog signals of commonly used thermocouples such as type K and type J. Using the millivolt measurement value of the process calibrator as a benchmark, the thermocouple output correction coefficient is adjusted to ensure that the temperature simulation output accuracy matches the calibration requirements of the hot runner temperature control channel.
RTD Signal Calibration: The signal generator is set to output resistance analog signals of commonly used RTDs such as Pt100 and Cu50. Using the resistance measurement value of the process calibrator as a benchmark, the RTD output correction coefficient is adjusted to ensure that the resistance analog output deviation is ≤ ±0.05%FS.
VI. Multi-Channel Synchronous Recalibration
Using the rising edge of the main channel output waveform as a benchmark, a multi-channel oscilloscope is used to simultaneously acquire the output signals of all slave channels, reading the phase time difference between each channel and the main channel.
Enter the "Delay Calibration" menu for each channel and fine-tune the channel delay correction coefficients until the synchronization deviation between all channels and the main channel is ≤0.01s.
If the synchronization trigger line length exceeds 200 meters, enable the device's cable resistance compensation function. The device will automatically calculate the transmission delay compensation based on the cable length and cross-sectional area to offset the synchronization deviation caused by long-distance transmission.
VII. Post-Calibration Verification and Parameter Solidification
After all calibrations are completed, randomly select 10 calibration points across the entire range and measure the output values one by one using a reference device to confirm that the accuracy deviation at all points is within the allowable range.
Run the device continuously for 30 minutes, collecting output accuracy and synchronization deviation data every 5 minutes to confirm that there is no instability due to drift over time.
Save all calibrated frequency correction coefficients, gain correction values, thermal signal correction coefficients, and delay correction coefficients to the device's non-volatile memory. These parameters will not be lost after a power outage and restart.
Record all parameter values from this calibration to generate a calibration file, providing a comparison benchmark for subsequent periodic recalibrations.
This detailed recalibration procedure is fully adapted to the industrial field operation and maintenance scenarios of hot runners. The operation process is clear and easy to implement, and can quickly complete the full-dimensional high-precision recalibration of hot runner signal generators.
