Raw Data Compression

The data is compressed automatically when the raw data is stored. For the signal value, data compression is achieved by storing the difference to the next data point instead of storing each data point separately. The actual value is stored only at intervals. In this way, the compression can be increased by 50%. This effect is especially noticeable with 3D Fields.

The size of the raw data file for a 3D field increases with the number of recorded data points. These depend on the Optical Resolution of the detector, field size (area between the upper and lower limit of the 3D field), and selected Sampling Rate.

For example, at a sampling rate of two spectra per second (step = 0.5) and an optical resolution of 2nm, this means that 2 x 60 x 70 = 8400 data points per minute must be recorded for the UV range from 200 to 340 nm. As each absorption value is recorded with an accuracy of 25 bits, a hard disk storage capacity of m x (N+1) x 4 = 70 x ((2x60)+1) x 4 = 33.88 kByte per minute is required. Thus, a storage capacity of 0.678 MByte is required for the 3D field of a "normal" (20-minute) chromatogram.

However, innovative data compression procedures allow reducing the required storage capacity by approximately 50-60% by storing only each eighth spectrum completely. For all other spectra, only the difference to the previous one is stored and re-calculated when needed. This procedure is a good compromise between optimum data compression and the required time for restoring a 3D field.

 Note:

The compression procedure is not destructive, that is, the complete data is stored. Thus, the 3D field contains the complete information provided by the detector. The data can be restored at any time.

There are three additional ways how you can minimize storage capacity requirements: