Portable Surface Roughness Tester - QualiSurf™ II / II-S

Inductive Contact Stylus Profilometry Principles

The QualiSurf™ II / II-S Series operates on the principle of contact stylus profilometry using a high-precision Inductance Pickup Transducer. Microscopic surface height deviations (R_a, R_z, R_q, etc.) generated by machining, grinding, honing, or turning are converted into quantitative electrical signals as the stylus traverses the workpiece.

                  ┌─────────────────────────────────────┐
                  │    Internal Drive Unit & Motor      │
                  └──────────────────┬──────────────────┘
                                     │
            ┌────────────────────────┴────────────────────────┐
            │   High-Precision LVDT Inductive Pickup Sensor   │
            └────────────────────────┬────────────────────────┘
                                     │
                         ┌───────────┴───────────┐
                         │ Diamond Stylus Tip    │  ──> (Traversing Workpiece)
                         └───────────┬───────────┘
                                     │
               ▲  ▲  ▲  ▲  ▲  ▲  ▲  ▲  ▲  ▲  ▲  ▲  ▲  ▲
               Microscopic Surface Profile (Peaks & Valleys)

Physical Measurement Physics

• Stylus Dynamics: A diamond tip with a selectable radius (2 μm or 5 μm) and angle (60° or 90°) tracks the physical surface profile. The stylus operates over a 45 mm skid curvature radius under a static measuring force (0.75 mN or 4.0 mN).
• Inductive Signal Modulation: Vertical excursion of the stylus modulates mutual inductance within the sensor coils, translating physical displacement into analog voltage across a total measurement range of 400 μm.
• High-Resolution Conversion: Internal signal electronics process analog signals into digital height data, offering automatic resolution scaling:
  • ±50 μm measuring range → 0.001 μm resolution
  • ±400 μm measuring range → 0.008 μm resolution

Traverse Speed Control

Measurement traverse speeds (V_t) automatically align with the selected cut-off length (λ_c) across a maximum drive length of 19 mm (0.748 in) with a 1.0 mm/s return speed:

• λ_c = 0.08 mm → V_t = 0.25 mm/s
• λ_c = 0.25 mm → V_t = 0.25 mm/s
• λ_c = 0.8 mm → V_t = 0.5 mm/s
• λ_c = 2.5 mm → V_t = 1.0 mm/s

Hardware Architecture & Application Methodology

Depending on physical workpiece geometry, two structural configurations are used to position the inductive pickup transducer:

Internal Diameter (ID) Inspection Methodology

Measuring internal surface finish, such as cylinder bore walls, valve bodies, or pipe interiors, requires decoupling the transducer driver from the instrument housing. The QualiSurf™ II-S split configuration isolates the external transducer pickup, allowing specialized bore probes to enter confined internal spaces for non-destructive surface evaluation.

Digital Signal Filtering & Parameter Computation

Raw displacement profiles contain a combination of micro-roughness, long-wavelength waviness, and form error. High-speed Digital Signal Processing (DSP) applies digital filtering to isolate the true roughness profile.

Raw Unfiltered Surface Profile (Form Error + Waviness + Roughness)
                            │
                            ▼
      [ Selectable Digital Filters: GAUSS (ISO 16610-21) / 2RC ]
                            │
                            ▼
               Evaluated Roughness Profile
                            │
    ┌───────────────────────┴───────────────────────┐
    ▼                                               ▼
45 Selectable Parameters                   Profile Graphs & Curves
(Roughness R, Primary P, Functional K)      (TFT Display / PC / Printer Output)

Digital Filtering Algorithms

• GAUSS (Gaussian): Phase-correct digital filtering per ISO 16610-21, preventing phase distortion across profile peak and valley calculations.
• 2RC Filter: Analog-equivalent filtering method for legacy specification compliance.
• Filter Cut-off Lengths (λ_c): 0.08 mm, 0.25 mm, 0.8 mm, and 2.5 mm.
• Evaluation Length (L_n): Selectable from (1 ~ 5)L.

45 Supported Parameters

The QualiSurf™ II / II-S calculates 45 distinct parameters across three profile categories:

1. Roughness Parameters (R)

• R_a (Arithmetic Mean Deviation): R_a = (1 / L) ∫ |y(x)| dx
• R_z (Maximum Height of Profile): R_z = R_p + R_v
• R_q (Root Mean Square Roughness): R_q = √[ (1 / L) ∫ y²(x) dx ]
• Additional R Metrics: R_p, R_v, R_t, R_sk, R_ku, R_c, R_Pc, R_Sm, R_mr(c), tp, R_mr, R_pm, R_z1max, R_zJIS, R_max, H_tp, R_δc, R_Δq, R_Δa.

2. Primary Parameters (P)

P_a, P_p, P_v, P_t, P_z, P_q, P_sk, P_ku, P_c, P_Sm, P_mr(c), P_mr, P_z1max, P_zJIS, P_δc, P_Δq.

3. Bearing Curve & Functional Parameters (K)

R_k, R_pk, R_vk, M_r1, M_r2, A₁, A₂: Computed from the Abbott-Firestone bearing area curve to quantify core roughness depth (R_k), reduced peak height (R_pk for initial wear), and reduced valley depth (R_vk for fluid/oil retention capacity).

Calibration & Compliance Standards

Electronic Calibration Method

To ensure traceable measurements under ISO 9001 and IATF 16949 quality standards, the instrument incorporates an automated software gain calibration routine (CAL key). Tracing the stylus across a certified glass or metal reference roughness standard automatically recalculates LVDT gain factors, compensating for transducer gain drifts or stylus wear.

Supported International Metrology Standards

• ISO 1997 / ISO 4287 / ISO 16610: Geometrical Product Specifications (GPS), Surface Texture & Gaussian Filtering
• ANSI / ASME B46.1: Surface Texture (Surface Roughness, Waviness, and Lay)
• JIS B0601 (2001): Japanese Industrial Standards for Surface Roughness Measurement