In order to prevent zero-point offset mistakes caused by temperature variations, turn on the new equipment and preheat it for at least half an hour. This will allow the internal circuitry to fully stabilise thermally.
To avoid signal interference from external devices compromising the accuracy of zero-point calibration, disconnect any external loads and leave the signal generator output port unoccupied.
As the traceability reference for zero-point measurement, prepare a reference process calibrator with an accuracy class > ±0.01% and link it to the signal generator output port.
Basic zero-point clearing procedure: To confirm entrance into zero-point calibration mode, navigate to the signal generator's system calibration menu and choose the "Zero Point Calibration/Drift Clearing" function.
In the current unloaded state, wait for the apparatus to automatically gather the real zero-point output value. Verify the difference between the theoretical zero-point value and the actual zero-point value as determined by the reference calibrator. This deviation will be automatically corrected by the apparatus to zero.
Verify the effectiveness of the zero-point correction by hand. To finish the basic zero-point clearing at this point, the zero-point output deviation as determined by the reference calibrator must be ≤ 0.01% of the range.
Zero-point calibration for several kinds of signals:
Voltage signal zero-point: To finish the voltage channel zero-point calibration, set the output to 0V DC voltage and make sure the deviation of the reference calibrator measurement value is ≤±1μV.
Current signal zero-point: To finish the current channel zero-point calibration, set the output to 0mA DC current and make sure the deviation of the reference calibrator measurement value is ≤±0.001mA.
Thermal signal zero-point: Adjust to the hot runner temperature control calibration scenario by setting the output to the thermocouple millivolt value that corresponds to 0°C and the RTD resistance value that corresponds to 0°C. Verify that the temperature deviation displayed by the hot runner temperature control system is ≤±0.5°C.
Verification of zero-point stability: After zero-point calibration, allow the apparatus to stand for half an hour before measuring the zero-point output value once again to ensure that there is no zero-point bounce and that the zero-point offset is less than 0.02% of the range.
To ensure that the zero-point drift is ≤0.03% of the range during an hour and that the zero-point condition is stable without continuous offset, run continuously for an hour, measuring the zero-point value every fifteen minutes.
In order to simulate a 0°C temperature signal across all channels, the system was linked to the hot runner temperature management system. It was verified that there were no signal jumps or problems with zero-point misalignment in any of the temperature control channels. After that, zero-point calibration was finished.
This straightforward and easily implementable zero-point calibration process swiftly removes zero-point reference discrepancies brought on by equipment replacement and establishes a solid basis for later full-range accuracy calibration.
