Microtest 6632+ vs 6350+ DC Bias Systems: Which One Fits Your Lab?

Microtest offers two distinct platforms for DC bias current testing of inductors and magnetic components: the 6632+ system built around an impedance analyzer, and the 6350+ system built around an LCR meter. Both measure inductance under DC bias, both scan Isat and Irms, and both include DCR measurement. The difference lies in the base instrument’s capabilities, and that difference determines which system fits your application.

The Core Distinction

The 6632+ system uses Microtest’s impedance analyzer as its measurement engine. The impedance analyzer provides a frequency range of 10 Hz to 50 MHz with equivalent circuit analysis capability. When paired with DC Bias Current Source modules, the combined system measures inductance under DC bias across a wide frequency span, with output currents up to 640 A.

The 6350+ system uses an LCR meter as its measurement engine. The LCR meter provides a frequency range of 100 Hz to 500 kHz, narrower than the impedance analyzer, but covering the frequencies most commonly used in production testing and incoming inspection. The 6350+ supports DC bias currents up to 320 A.

Specification Comparison

Feature	6632+ (Impedance Analyzer)	6350+ (LCR Meter)
Frequency range	10 Hz to 50 MHz	100 Hz to 500 kHz
Max DC bias current	Up to 640 A	Up to 320 A
Equivalent circuit analysis	Yes	No
Isat scanning	Yes	Yes
Irms scanning	Yes	Yes
DCR measurement	Yes	Yes
PC Link software	Yes	Yes
Base instrument	Impedance analyzer (6632S series)	LCR meter

When to Choose the 6632+

R&D characterization. If your application requires measuring inductor behaviour across a wide frequency range, understanding how saturation characteristics shift between 100 kHz and 10 MHz, the 6632+ provides data that the 6350+ cannot. This matters for power inductor designs targeting high switching frequencies (500 kHz to 2 MHz) where frequency-dependent core losses and permeability changes affect inductor selection.

Equivalent circuit extraction. The 6632S impedance analyzer extracts lumped-element equivalent circuit models from measured impedance data. For engineers who need SPICE models of inductors under DC bias, the 6632+ system provides this capability directly.

High-current testing above 320 A. The 6632+ system supports DC bias current source modules up to the 6243H, reaching 640 A. For high-current automotive and server power inductors, this headroom is essential.

Material characterization. Core material manufacturers and magnetic component designers who need permeability versus bias data across a broad frequency range will benefit from the impedance analyzer’s extended bandwidth.

When to Choose the 6350+

Production testing and incoming inspection. The 6350+ is designed as an integrated production test system. If your primary need is verifying Isat and Irms on incoming power inductors at standard test frequencies (typically 100 kHz or below), the 6350+ provides the measurement capability needed at a lower system cost.

Cost-sensitive applications. The LCR meter base instrument carries a lower price point than the impedance analyzer. For quality labs and production lines where the extended frequency range and equivalent circuit features of the 6632+ are unnecessary, the 6350+ delivers the essential DC bias measurements at reduced investment.

Current requirements up to 320 A. For inductor sizes where 320 A maximum bias current is sufficient, which covers the majority of commercial and industrial power inductors, the 6350+ provides adequate current range.

Shared Capabilities

Both systems provide the core measurements that matter for power inductor characterization:

Isat scanning: automated inductance-versus-current sweeps that generate saturation curves, identifying the current at which inductance drops below a specified percentage threshold.

Irms scanning: temperature rise current measurement using copper temperature coefficient analysis, evaluating thermal limits independently of magnetic saturation.

DCR measurement: four-wire DC resistance measurement for efficiency loss calculations.

PC Link software: data export, graphical analysis, and test sequence programming from a connected PC.

Both systems support current/frequency graphic scanning analysis and graphical display of inductance drop percentage.

A Practical Decision Framework

If your team primarily tests inductors on the production line or at incoming inspection, and your test frequencies are 500 kHz or below, start with the 6350+. If you later need wider frequency characterization or higher currents, the 6632+ can be added alongside or as an upgrade path.

If your team designs power converters, characterizes new inductor designs, or needs SPICE-compatible component models, the 6632+ pays for itself in engineering time saved by providing the comprehensive data set in a single measurement session.

Availability in India

GSAS is Microtest’s authorized engineering partner in India, providing both the 6632+ and 6350+ DC Bias systems with local demonstration, installation, training, and calibration support. Our applications engineers help teams across Bengaluru, Hyderabad, Chennai, Pune, Mumbai, Delhi NCR, and Visakhapatnam select the right system configuration for their testing requirements and budget.

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