Calibration may be required:
- After battery testing system has been repaired or modified.
- When a specified time period has elapsed.
- When a specified usage (operating hours) has elapsed.
- Before and/or after a critical battery testing activity.
- After an event, for example
- After the battery testing system has had a shock, vibration, or has been exposed to an adverse condition which potentially may have put it out of calibration or damage it.
- Sudden changes in weather.
- Improper use of software to cause the loss of the calibration data.
- Whenever observations appear questionable or battery testing system indications do not match the output of surrogate instruments.
- As specified by a requirement, e.g., customer specification.
Calibration, in general use, is often regarded as including the process of adjusting or aligning the output of or indication on the equipment to agree with value of the applied standard, within a specified accuracy.
Neware battery testing system generally outputs and measures current and voltage. And it has different circuits for charge and discharge. So we need to calibrate a). Charge Current; b). Discharge Current; c). Charge Voltage; d). Discharge Voltage.
- Charge Current / Discharge Current (If negative power supply installed)
Since standard current meters generally cannot support large current, a DC shunt should be introduced for large current calibration. The current value given by the battery testing system should be compared to the measured current through the shunt.
Figure 78 : Current Calibration Connection Diagram
- Discharge Current (No negative power supply installed)
If there is no negative power supply installed, the battery testing system cannot discharge unless you connect a battery which functions as a power supply and the battery testing system functions as a load. You can calibrate discharge current at this situation just string a battery in the circuit as above diagram in Charge Current / Discharge Current (If negative power supply installed) section . You need to consider the discharge capability of the battery connected.
- Charge Voltage
Now string a resistor in the circuit as below diagram, set constant voltage charge, this will create a voltage at the ends of the resistor. Neware battery testing system will read a voltage value, the external meter will also read a voltage value. These values will be used for the calibration.
Figure 79 : Voltage Calibration Connection Diagram
- Discharge Voltage
For the equipment with negative power supply and empowered with Constant Voltage Discharge, you can use the same logic as above or calibration of the charge voltage. If this is not possible, a digital voltage signal source needs to be introduced for the calibration.