calibration file format

Calibration File Format

The RocketLogger uses linear calibration to convert the analog-digital converted measurements to physical units. The offset and scale values of this calibration are stored in a binary file that is loaded by the RocketLogger software.

To output the raw measurement data output from the analog-to-digital converters, a virtual calibration consisting of offset 0 and scale 1.0 is applied during recalibration measurements.

Calibration File Format Version 2

The data of the RocketLogger calibration is stored in little-endian format and stores the data listed in the table below.

Offset	Size (byte)	Field	Content
0x00	4	Magic Number	%RLC (= 0x434C5225) magic number (unsigned integer)
0x04	2	File Version	Current file version number, i.e. 0x02 (unsigned integer)
0x06	2	Header Length	Total header length in bytes, i.e. 0x10 (unsigned integer)
0x08	8	Timestamp	Timestamp of oldest measurement used for calibration in UNIX seconds (UTC)
0x10	4	V1 Offset	Offset of channel V1 in bit (integer)
0x14	4	V2 Offset	Offset of channel V2 in bit (integer)
0x18	4	V3 Offset	Offset of channel V3 in bit (integer)
0x1C	4	V4 Offset	Offset of channel V4 in bit (integer)
0x20	4	I1L Offset	Offset of channel I1L in bit (integer)
0x24	4	I1H Offset	Offset of channel I1H in bit (integer)
0x28	4	I2L Offset	Offset of channel I2L in bit (integer)
0x2C	4	I2H Offset	Offset of channel I2H in bit (integer)
0x30	4	DT Offset	Offset of channel DT in bit (integer)
0x34	8	V1 Scale	Scale of channel V1 in 10nV/bit (double)
0x3C	8	V2 Scale	Scale of channel V2 in 10nV/bit (double)
0x44	8	V3 Scale	Scale of channel V3 in 10nV/bit (double)
0x4C	8	V4 Scale	Scale of channel V4 in 10nV/bit (double)
0x54	8	I1L Scale	Scale of channel I1L in 10pA/bit (double)
0x5C	8	I1H Scale	Scale of channel I1H in nA/bit (double)
0x64	8	I2L Scale	Scale of channel I2L in 10pA/bit (double)
0x6C	8	I2H Scale	Scale of channel I2H in nA/bit (double)
0x74	8	DT Scale	Scale of channel DT in ns/bit (double)

Total file size: 124 bytes

Calibration File Format Version 1

Up to and including RocketLogger versions 1.x, the file format detailed below was used. This unversioned format is considered file format version 1. All file data is stored in little-endian format.

Offset	Size (byte)	Field	Content
0x00	8	Timestamp	Timestamp of oldest measurement used for calibration in UNIX seconds (UTC)
0x08	4	I1H Offset	Offset of channel I1H in bit (integer)
0x0C	4	I1L Offset	Offset of channel I1L in bit (integer)
0x10	4	V1 Offset	Offset of channel V1 in bit (integer)
0x14	4	V2 Offset	Offset of channel V2 in bit (integer)
0x18	4	I2H Offset	Offset of channel I2H in bit (integer)
0x1C	4	I2L Offset	Offset of channel I2L in bit (integer)
0x20	4	V3 Offset	Offset of channel V3 in bit (integer)
0x24	4	V4 Offset	Offset of channel V4 in bit (integer)
0x28	8	I1H Scale	Scale of channel I1H in nA/bit (double)
0x30	8	I1L Scale	Scale of channel I1L in 10pA/bit (double)
0x38	8	V1 Scale	Scale of channel V1 in 10nV/bit (double)
0x40	8	V2 Scale	Scale of channel V2 in 10nV/bit (double)
0x48	8	I2H Scale	Scale of channel I2H in nA/bit (double)
0x50	8	I2L Scale	Scale of channel I2L in 10pA/bit (double)
0x58	8	V3 Scale	Scale of channel V3 in 10nV/bit (double)
0x60	8	V4 Scale	Scale of channel V4 in 10nV/bit (double)

Total file size: 104 bytes

Calibration File Format Revisions

1. Calibration file format used for RocketLogger software versions 1.x.

   Remarks:

   • this unversioned file format is considered version 1 of the format

2. Additions:

   • file header magic number
   • file format version
   • file header length
   • calibration values for DT channel, i.e. the PRU sampled time interval between measurement samples

   Changes:

   • sort channel by measured unit

   Remarks:

   • first versioned calibration file format