UL 921 Figure 3 PA140B Test Probe for Film-Coated Wire Insulation Integrity Verification

UL 921 Figure 3 PA140B Test Probe for Film-Coated Wires is a precision safety testing instrument engineered to verify the insulation integrity of film-coated electrical conductors in compliance with UL 921 standards. This specialized tool detects microscopic cracks, pinholes, or coating defects that could lead to electrical leakage hazards in scientific, industrial, and medical auxiliary equipment applications.

The probe features a conductive brass tip with controlled dimensional specifications for precise surface contact with film-coated wires, while the insulating nylon handle provides operator protection against electrical shock during testing procedures. Engineered to apply minimal, controlled contact pressure, the instrument simulates real-world operational conditions while maintaining strict adherence to UL 921 testing protocols.

Manufacturers and testing laboratories utilize this durable, dimensionally stable probe to ensure film-coated wires meet U.S. safety standards for electrical insulation performance. The instrument’s design prevents damage to intact film coatings while reliably identifying insulation defects that could compromise electrical safety.

Technical Specifications

• Probe Type: UL 921 Figure 3 Test Probe for film-coated wire insulation integrity verification
• Probe Tip Material: Brass (high conductivity, corrosion-resistant for reliable electrical contact)
• Handle Material: Nylon (fully insulating, heat-resistant, non-slip surface for precise pressure control)
• Key Dimensions:
  • Probe Tip Diameter: 1.5 mm ± 0.05 mm (optimized for small-diameter film-coated conductors)
  • Effective Probe Length: 25 mm ± 0.2 mm
  • Handle Length: 100 mm ± 0.5 mm
  • Total Length: 125 mm ± 0.5 mm
• Electrical Conductivity: Probe tip resistance ≤ 0.1 Ω (ensures accurate leakage current detection)
• Applied Force: Minimal contact pressure (prevents damage to intact film coatings)
• Primary Function: Detection of insulation defects (cracks, pinholes, coating damage) in film-coated wires per UL 921 standards

Testing Procedure

1. Inspect the probe assembly for physical integrity (straight tip, undamaged handle, verified conductivity) and connect to appropriate leakage detection instrumentation.
2. Prepare the film-coated wire specimen—ensure surface cleanliness, dryness, and placement on a non-conductive testing surface.
3. Grasp the insulating handle and align the brass probe tip perpendicular to the wire’s film coating surface.
4. Apply light, uniform contact pressure while traversing the probe along the wire’s longitudinal axis.
5. Monitor the leakage detection instrument for indications of insulation defects during the testing sequence.