In any testing or manufacturing environment that utilizes electronic circuitry, the power supply is the fundamental source of energy. Its function is to provide highly stable, clean, and accurately regulated DC or AC voltage and current. Therefore, power supply calibration is essential to ensure that the output parameters match the display readings and meet the demands of the Device Under Test (DUT). Errors in power supply output—such as excessive ripple, incorrect voltage, or current instability—can lead to mischaracterization of components, false test failures, or, in high-power applications, component damage.
The Technical Requirements of Power Supply Calibration
Power supply calibration is complex because it must verify multiple interacting parameters under various load conditions. The goal is to verify that the output remains stable and accurate across the entire operating range.
Key parameters verified during calibration include:
- Voltage Accuracy: Checking the output voltage against a high-accuracy reference multimeter across the range, with and without load.
- Current Accuracy: Verifying the output current accuracy using a high-precision shunt or clamp meter.
- Ripple and Noise: Measuring the residual AC signal (ripple) present in the DC output. Excessive ripple can compromise sensitive digital circuits.
- Regulation (Line and Load): Verifying the power supply’s ability to maintain a stable output despite changes in the input AC voltage (line regulation) or changes in the resistance of the DUT (load regulation).
The Impact of Drift and Degradation
Power supplies are prone to drift due to the aging of internal components like electrolytic capacitors and voltage reference chips. This aging causes the voltage reference to shift and can increase ripple over time. This internal drift means the power supply’s front panel display may show 5.000 V, while the actual output delivered to the DUT is 5.050 V, a deviation that can easily push a sensitive circuit out of its operational limits.
The Rigor of Load and Line Regulation Testing
A superficial calibration might only check the power supply’s output under a no-load condition, which is insufficient for real-world testing. Rigorous power supply calibration must include a detailed check of load regulation. This involves applying certified resistive loads (which simulate the DUT) to draw significant current while monitoring the voltage output with a highly stable multimeter. The technician measures the instantaneous change in voltage when the load is applied or removed. Similarly, line regulation testing involves verifying the output stability while changing the input AC mains voltage. Errors in regulation performance indicate failing internal components, such as MOSFETs or control loop circuitry, which require repair before a successful calibration can be performed.
Actionable Maintenance and Troubleshooting
A common best practice is to always measure the output voltage directly at the DUT, compensating for any voltage drop in the leads. Furthermore, calibration should always be performed under load conditions that mimic the power supply’s intended use, as calibration without load fails to expose potential regulation issues.
Choosing an Accredited Partner
Due to the fundamental role of power supplies in all electrical testing, their calibration must be traceable and accredited. A qualified provider must have the necessary master standards (high-stability reference meters and low-impedance loads) to test the power supply’s output under full operational stress.SIMCO provides ISO/IEC 17025 accredited power supply calibration services, verifying all critical parameters including ripple, noise, and regulation, ensuring the power source meets the highest standards of stability required for precision electronics testing.
Integrated Calibration and Repair
When a power supply fails, it often requires component-level repair before it can be calibrated. A provider that offers integrated repair and calibration streamlines the process. SIMCO’s technical teams can diagnose and replace failed power components, and then immediately move the unit to the calibration bench. This guarantees that the unit is not only functional but also certified to deliver accurate, stable power, minimizing downtime and providing complete confidence in the integrity of the electrical source. Clients can find specific details on SIMCO’s electrical capabilities and service offerings via a local calibration laboratory, such as the one in Allentown, PA.
