Load Leads, Remote Sense Points | Agilent Technologies 669xA, 665xA

OVP Considerations

The power supply OVP circuit senses voltage near the output bus bars, not at the load. Therefore the signal sensed by the OVP circuit can be significantly higher than the actual voltage at the load. When using remote sensing, you must program the OVP trip voltage high enough to compensate for the voltage drop between the output bus bars and the load.

Output Rating

In remote sense applications, the voltage drop in the load leads subtracts from the available load voltage. As the power supply increases its output to overcome this voltage drop, the sum of the programmed voltage and the load-lead drop may exceed the power supply's maximum voltage rating. This will not damage the supply, but may trip the OV protection circuit, which senses the voltage at the output bus bars. When the supply is operated beyond its rated output the performance specifications are not guaranteed, although typical performance may be good.

Output Noise

Any noise picked up on the sense leads may appear at the output of the supply and can adversely affect the voltage load regulation. Use shielded twisted pairs for the sense leads and route them parallel and close to the load leads. Ground the shields only at the power-supply end, utilizing the signal ground binding post. Do not use a shield as one of the sense conductors. Bundle or tie-wrap the load leads to minimize inductance and reduce noise pickup.

Stability

Using sensing under unusual combinations of load lead lengths and large load capacitances may cause your application to form a low-pass filter, which becomes part of the voltage feedback loop. The extra phase shift created by this filter can degrade the supply's stability, resulting in poor transient response. In severe cases, it may cause oscillation. To minimize this possibility, keep the load leads as short as possible and tie wrap them together.

In most cases, following these guidelines will eliminate problems associated with load lead inductance. However, if a large bypass capacitor is required at the load and load-lead length cannot be reduced, then a sense-lead bypass network may be needed to ensure stability (see Figure 4-5b).

The voltage rating of the 33 ∝F capacitors should be about 50% greater than the anticipated load-lead drop. Addition of the 20 Ω resistors will cause a slight voltage rise at the remote sensing points. For utmost voltage programming accuracy, the supply should be recalibrated with the DVM at the remote sensing points (see “Appendix A - Calibration”). In addition, the sense protect resistors inside the power supply may have to be removed. (If you need help with a stability problem, contact an Support Engineer through your local Agilent Sales and Support offices.)


Load Leads	C3 = Load bypass capacitor	Remote Sense Points
C1, C2 = 33∝F	C3 = Load bypass capacitor	Rl, R2 = 20 Ω, 1%

Figure 4-5b. Series 668xA and 669xA Sense Lead Bypass Network

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668xA, 669xA, 667xA, 664xA, 665xA specifications

Agilent Technologies has long been a pioneer in the production of high-performance electronic test and measurement instruments, particularly in the field of power sources. Among its notable offerings are the Agilent 667xA, 669xA, 665xA, 664xA, and 668xA series of power supplies. These instruments are designed to provide stable, reliable power for a variety of applications, including electronic testing, industrial processes, and research laboratories.

The Agilent 667xA series is characterized by its programmability and advanced measurement functions. These power supplies support a wide range of output voltages and currents, allowing for flexible configurations that cater to different testing needs. The built-in measurement capabilities enable users to monitor the voltage, current, and power with high precision, which is essential for ensuring optimal performance in electronic applications.

The Agilent 669xA series stands out with its high-power outputs, making it suitable for demanding applications. These power supplies deliver high voltage and current levels, making them ideal for testing high-performance devices, such as power amplifiers and motor drives. Additionally, the 669xA series includes features such as overvoltage protection and complex output sequencing to enhance the safety and reliability of the testing process.

The Agilent 665xA and 664xA series focus on delivering high accuracy and excellent regulation. These models are particularly known for their low noise operation, which is critical for sensitive applications where precision is paramount. The integrated programming capabilities allow users to automate testing sequences, thus improving efficiency in research and development settings.

The 668xA series features advanced digital signal processing that enhances the precision and stability of the output. Users benefit from features like remote sensing and monitoring, allowing feedback adjustments that maintain output accuracy despite cable losses. Furthermore, the 668xA models can integrate seamlessly with various test environments thanks to their LAN, GPIB, and USB connectivity options.

Overall, the Agilent 667xA, 669xA, 665xA, 664xA, and 668xA power supplies provide a comprehensive range of solutions for diverse electronic testing needs. With their advanced features, superb measurement capabilities, and robust performance, these instruments empower engineers and researchers to conduct their work with confidence, precision, and efficiency.