Portable Hardness Tester – Computest-Lite

The Computest Lite operates on the static low-load Rockwell measurement principle governed by DIN 50157 and ASTM E18 standards. The method determines material hardness by applying a preliminary force (preload) followed by a major load, measuring the residual depth of penetration (Δh) left by a single diamond cone indenter.

Unlike dynamic methods that calculate hardness indirectly through kinetic energy rebound (Leeb) or acoustic frequency shifts (UCI), the Computest Lite applies a pure static force of 5 kgf (49 N). This static load creates a direct physical depth measurement, removing variables such as component elastic modulus, specimen weight, or structural mass resonance.

Two-Stage Force Mechanics & Depth Measurement

1. Preload Baseline (1.2 kgf / 11.8 N): Pressing the instrument against the material drives an outer reference shroud onto the surface to create an exact zero-point baseline. A 1.2 kgf force pushes the diamond cone past surface oxidation and minor machining marks.
2. Major Load Penetration (5 kgf / 49 N): Applying the full 5 kgf major force drives the diamond indenter deeper into the material while the reference shroud holds the zero position on the outer surface.
3. Residual Depth Differential (Δh): Upon releasing the major load back to the preload state, the internal sensor measures the exact depth difference between the initial baseline and the final indenter position. This depth value directly converts into standard scale values including HRC (10–70), HRB (0–120), HB30 (80–700), HB5 (21–190), HV (35–1080), and tensile strength (N/mm²).

Because force application is static, measurement accuracy remains unaffected by testing direction, operating consistently across 360-degree orientations.

Method Comparison: Static Rockwell vs. Dynamic & Acoustic Testing

Mechanics of Thin Material & Zero-Mass Testing

• Elimination of Structural Flex: Impact rebound testing causes thin wall sections to bend under kinetic shock, dissipating impact energy and yielding artificially low hardness values. The 5 kgf static load of the Computest Lite penetrates without triggering structural deflection, allowing precise measurements on sheet metal down to 0.1 mm.
• Elimination of Mass Resonance: Ultrasonic probes depend on stable acoustic waves; lightweight parts under 300 grams vibrate along with the sensor tip, destroying measurement stability. The static depth method eliminates acoustic resonance, enabling weight-independent testing on loose components.

Surface Conditions & Standard Ratios

To satisfy DIN 50157 criteria and maintain a repeatability tolerance of ±0.3 HRC:

• Surface Roughness: Test surfaces require smooth preparation, targeting a roughness of Ra ≤ 1.6 μm to prevent indenter tilting.
• Minimum Layer Depth: When testing surface-hardened or nitrided layers, total case thickness must exceed at least ten times the final penetration depth (Δh) to avoid core substrate influence.