VTI Instruments Corp.
APPENDIX D
108
adjustments are stored in human readable JSON format. If necessary, the user can edit the constants
and keep them as full-calibration.
To perform factory calibration, a fully calibrated precision instrument and setup is required. The
factory calibration is usually generated by VTI or authorized calibration facility. If the user wishes
to perform factory calibration at their own facility, contact to VTI for more information.
S
ELF
/F
ULL
C
ALIBRATION
A
DJUSTMENTS
F
ILE
Calibration adjustments files are JSON documents organized as a series of nested JSON Objects
(lists of key-value pairs). The following list of keys and the description of their values mimics the
nested structure of the calibration files. Many keys are only present on some models.
•
Date: YYYY-MM-DD HH:mm:SS
•
Type: Full or Self
•
Instrument:
o
Model: model number
o
Serial: serial number
o
Version: version number
o
Daughter Card:
▪
Model: model number
▪
Serial: daughter card serial number
•
Adjustments:
o
Channels:
▪
CH1 - CHN: list of calibration objects, each containing:
•
Range: The range that these constants apply to
•
Clock Frequency: The setting of
SamplingClockFrequency
that these constants apply
to
•
Offset: Calibration offset in ADC counts
•
Offset_AC: If present, the offset to use when Coupling=AC
•
Gain: Calibration gain, unitless
o
IEPE Channels:
▪
CH1 - CHN:
•
High: If present, the value of the high IEPE source in Amps
•
Low: If present, the value of the low IEPE source in Amps
•
Offset: If present, the calibration offset of the IEPE source, in counts
•
Gain: If present, the calibration gain of the IEPE source, in amps per count
•
Load: A test value obtained by running the IEPE source through an internal load
resistor
o
Charge_Gain:
▪
CH1 - CHN: Additional gain that is combined with channel gain when Function=Charge
•
References:
o
Channels:
▪
CH1 - CHN:
•
nHz: reference measurements for the specified Clock Frequency
o
Various model-specific reference voltage measurements, as measured by an
external DMM
