Prior to zero point correction, preparation
For the internal analogue circuit to be completely thermally stable and to prevent further zero drift mistakes brought on by temperature variations, the apparatus must be turned on and preheated for at least half an hour.
To prevent signal interference from external devices impacting the precision of zero-point adjustment, disconnect any external loads and keep the signal generator's output port unoccupied.
As a traceable reference for zero point measurement, prepare a reference process calibrator with an accuracy level of ≥±0.01% and link it to the signal generator's output port.
Simple zero cleaning procedure
Choose the "Zero Calibration/Drift Clear" special function from the signal generator system calibration menu, then switch to the zero adjustment mode.
In the current no-load state, wait for the equipment to automatically gather the actual zero output value. Then, verify the difference between the theoretical zero value and the actual zero value as determined by the reference calibrator. The equipment will then automatically correct the difference and return the output value to zero.
Verify by hand that zero point compensation is applied. At this step, the basic zero point clearing is finished if the zero point output deviation as determined by the reference calibrator is ≤ 0.01% of the range.
For thermal conditions, a unique zero point calibration
Zero point of the voltage signal: Verify that the reference calibrator's measurement value deviation is ≤±1μV, set the output DC voltage to 0V, and finish the voltage channel zero point calibration.
Zero point of the current signal: Verify that the reference calibrator's measurement value deviation is ≤±0.001mA, set the output DC current to 0mA, and finish the current channel zero point calibration.
Zero point of thermal signal: Set the thermal resistor resistance value to 0°C and the output thermocouple millivolt value to 0°C. Verify that the hot runner temperature control system adjusts to the hot runner temperature control calibration scenario by displaying a temperature variation of ≤±0.5°C.
Verification of zero point stability
To ensure that there is no zero point rebound and that the zero point offset is less than 0.02% of the range, let the device stand for half an hour after the zero point adjustment is finished, then measure the zero point output value once more.
Run continuously for one hour, measure the zero point value every fifteen minutes, and verify that the zero point state is stable without continuous variation and that the zero point drift within the hour is less than 0.03% of the range.
Connect to the hot runner temperature control system, simulate a 0°C temperature signal in each channel, and verify that all temperature control channels display as intended, that there are no signal jumps or zero point misalignment issues, and that all zero point adjustments have been made.
The zero reference deviation can be swiftly eliminated with this simple set of adjustment processes, which can also prevent zero-point drift, which can lead to inaccurate hot runner temperature control calibration, and provide a solid basis for subsequent full-scale accuracy calibration.
