Testo offers a variety of calibration services for its instruments. The number on the left is the part number for that particular service. • 400520 1901 - NIST Temperature Certificate, 3 standard points: +10°C, +25°C, +40°C; or 20°C, +25°C, +40°C • 400520 1902 - NIST Temperature Certificate, 3 Custom Points • 400520 1911 - NIST Temperature Certificate for IR Thermometers • 400520 1913 - NIST Temperature Certificate • 400520 2601 - NIST RH Certificate with 2 Standard Points 11.3% and 75.3% RH • 400520 2602 - NIST RH Certificate 2 Custom Point • 400520 3301 - Calibration service - One (1) Gas & NIST • 400520 4401 - NIST Air Velocity Certificate 3 Standard Points • 400520 4402 - NIST Air Velocity Certificate, 3 Custom Points • 400520 4403 - NIST Flow Hood Certification • 400520 5801 - NIST Sound Certificate • 400520 6401 - NIST Tachometer Certificate • 400520 7501 - NIST Pressure Certificate • 400520 8501 - NIST Light Certificate