For direct measurement with reference instruments, empty the signal generator output port and disconnect all external loads. Using a reference process calibrator with an accuracy class of ≥ ±0.01%, directly measure the output value at zero point.
Zero-point offset is directly calculated if the actual DC voltage zero-point output deviates from the theoretical zero point by more than ±1μV or the DC current zero-point deviation is greater than ±0.001mA.
Particular Determination for Thermal Signals: Zero-point offset is identified if the thermocouple millivolt zero-point variation is greater than ±0.5μV or the Pt100 RTD zero-point resistance deviation is greater than ±0.01Ω.
Stability Trend Determination: For one hour, continually collect zero-point output data every fifteen minutes after the equipment has been turned on and preheated for thirty minutes. Zero-point offset is calculated if the zero-point drift is greater than 0.03% of the range.
Zero-point offset is identified if, following a small vibration of the equipment casing, the zero-point output fluctuation persists for more than two seconds without naturally settling.
Environmental Correlation Determination: A temperature-induced zero-point offset is identified if the drift abruptly rises to more than 200% of the zero-point deviation at room temperature within the typical ambient temperature range of -10°C to 60°C.
A mechanical stress-induced zero-point offset is identified if the equipment installation position is changed from horizontal to vertical and the zero-point output discrepancy is greater than 0.5% of the range.
Hot Runner System Interaction Determination: A temperature difference between the temperature shown on the temperature control channel and the theoretical zero-point temperature exceeding ±0.5°C is determined to indicate a zero-point offset when connected to the hot runner temperature control system, with all channels outputting the thermal simulation signal corresponding to 0°C.
A zero-point offset is found in the signal generator if the temperature display shows erratic jumps while the hot runner temperature control channel is not heating and the issue still exists after thermocouples and the temperature controller are checked.
A zero-point offset in the equipment is confirmed if any one of these determination criteria is met. In order to avoid injection moulding flaws and incorrect hot runner temperature control calibration due to zero-point drift, zero-point calibration must be done as soon as possible.
