QuadTech / Chroma Ground Bond Tester. Model: Sentry 50 Plus ( Chroma Model: 19572). G15 – Ground Continuity Lead Set. Accuracy: ±(1.5% of setting + 0.15A). Resistance Accuracy: 10-30A, 10-150mΩ: ±(1% reading +1mΩ) / All other ranges: ±(2% of reading +2.6mΩ).