The AX series is a range of precision wirewound resistors in moulded axial leaded construction, offering tolerance grades down to ±0.01% and temperature coefficients of resistance (TCR) as low as ±10 ppm/°C across the majority of its resistance range. Wirewound construction — in which a calibrated resistance wire is wound onto a ceramic or insulating former and then precisely trimmed to value — is the established technology for achieving the very tightest resistance tolerances in a leaded component. The wound element provides lower noise, greater inherent stability under sustained load, and better reproducibility of resistance value than deposited film techniques, at the cost of higher inductance that must be managed in AC and high-frequency applications. The AX15L, the single current model in the series, has a 15mm body length and 7mm body diameter, rated at 1W continuous power dissipation.
The resistance range spans 1Ω to 400kΩ, with TCR differentiated by resistance value: ±15 ppm/°C applies to values from 1Ω to 19.9Ω, where winding geometry constraints at very low resistance values make the tighter ±10 ppm/°C grade impractical, while ±10 ppm/°C is achieved for all values at 20Ω and above. Three tolerance grades are offered: ±0.1% (grade B), ±0.05% (grade A), and ±0.01% (grade T). The ±0.01% tolerance grade, in particular, is a level of initial accuracy that approaches reference-standard performance and is typically reserved for calibration, metrology, and the most demanding measurement instrument designs. The combination of ±0.01% tolerance and ±10 ppm/°C TCR in a single 1W leaded package is a specification that most film-type resistors cannot match.
The moulded construction of the AX series encapsulates the wound resistive element completely, providing robust protection against moisture ingress, solvent exposure, and mechanical damage. Moisture resistance is qualified to MIL-STD-202, and the component withstands 1,000V AC dielectric stress for one minute with a maximum leakage current of 2mA, confirming suitability for use in circuits operating at elevated voltages. The 2,000-hour load life test at 70°C with rated power applied shows a drift limit of ±0.1%, demonstrating the long-term stability that distinguishes precision wirewound types from both thick film and standard metal film alternatives. Temperature cycling between −30°C and +100°C confirms the mechanical integrity of the wound element and moulded housing across typical industrial temperature excursions.
Within the RARA precision resistor family, the AX series occupies the leaded wirewound precision segment alongside the CE-CL-T, 5G10, 8G16, and GG102 series. It offers a broader resistance range than many of those types — reaching 400kΩ — in a 1W rated body that is physically larger and more power-capable than the smaller wirewound types, while remaining a conventional axial leaded component fully compatible with through-hole PCB assembly, resistor sockets, and manual wiring in panel and chassis applications. An ultra-precision grade is noted as available for demanding applications requiring performance beyond the standard catalogue specification.
