HBK Bruel & Kjaer 3670-A-082, User Manual

Page: 29 / 36

21
Chapter 4
Calibration
4.1 Factory Calibration
Every Type 3670 is delivered with a Factory Standard Calibration Certificate. The certificate can be found
on the USB memory stick delivered with the instrument.
Factory standard calibration provides detailed calibration information and measured results on the
individual instrument for all input and output channels.
Input channel calibration information:
• Frequency response
• Harmonic distortion
• Noise
• Gain correction
• DC offset
Output channel calibration information includes:
• Frequency response
• Harmonic distortion
• Noise
4.2 Using the Input Gain Correction and DC Offset Information
The information provided in the calibration certificate can be used to calculate the corrected measured
level
Corrected Measured (V) = (sample / DIG_FS) * ANA_FS * Gai DC_Offset
where:
DIG_FS is digital full-scale
ANA_FS is analogue full-scale
Gain_corr is the gain correction for the selected channel
DC_Offset is the DC offset for the selected channel
Example:
Assume that our measurement software receives a level corresponding to a maximum digital level from
Type 3670 Input Channel 1 and we want to know the actual input level in volts. In the Calibration
Certificate we find:
Gain_Corr for Ch. 1 = 0.994375