TGA files and variables summary
This reference section provides a summary of files and variables related to TGAs and the LI-6800.
Calibration files
Calibration files include information describing the calibration tanks and adjustments made during a calibration.
Tank files
These describe the sources of calibration gas. Tank files are saved in the home/licor/logs/tga/tanks directory. They contain a json map, with gas names as keys. They are created when you do the procedure described in Adding tanks. Listing 12‑1 shows an example added by the +CO2 Iso Tank button, and Listing 12‑2 a tank added by the +Other Tank button.
Listing 12‑1. Example tank file (CO2_1000_-30_dO18_-12_dO17_-4.json).
{
"CO2": 1000,
"dC13": -29.7,
"dO17": -3.5,
"dO18": -12.1,
"C12": 984.3714,
"C13": 10.733,
"O18": 4.0617,
"O17": 0.7751
}Listing 12‑2. Example tank file (ch4_2ppm_N2O_0ppm). Tanks added by +Other Tank carry explicit units.
{
"CH4”: {
"value": 2.07,
"units": “ppm"
},
"N2O": {
"value": 0.355,
"units": “ppm”
}
}Tank Measurement (TM) Files
TM files are saved in the home/licor/logs/tga/tanks/events/<serial> directory. They are created manually by tapping the Capture button (Figure 12‑45), or under program control (Capturing a Tank Measurement).
Listing 12‑3. Example TM file.
{
"id": "TM0171",
"time": "2025-08-12 14:20:49",
"tank_name": "1000_-30_-4_-12",
"tank_on_secs": "01:56", //How long the tank has been on (minutes:seconds)
"tank_cal": { //The associated tank cal file
"CO2": 1000,
"dC13": -29.7,
"dO17": -3.5,
"dO18": -12.1,
"C12": 984.3714,
"C13": 10.733,
"O18": 4.0617,
"O17": 0.7751
},
"deltas": { //Measured (from data, below) - true (from tank_cal, above)
'CO2': -0.1,
'dC13': -0.02,
'dO18': -0.04,
'dO17': -0.34,
'C12': -0.0407,
'C13': -0.0006,
'O18': -0.00039,
'O17': -0.00024
},
"tga_cal": { //The TGA cal at time of measurement
"sn": "TG25-01057",
"latest_atm": "ATM0099",
"Offset_Cal_C12": 0.42998502194008736,
"Offset_Cal_C13": 0.12068877735539418,
"Offset_Cal_O18": 0.027400889754766827,
"Offset_Cal_O17": -0.0014,
"C12_Span": 1.0172029290401823,
"C13_Span": 1.0162836221967664,
"O18_Span": 1.0084701300925054,
"O17_Span": 0.9331608051073214
},
"data": { //The TGA_stats group at time of measurement
"period": 40,
"H2O": -55.893053724999994,
"H2O_sd": 5.764644894481073,
"H2O_slp": -27.75925959600212,
"CO2": 999.9481739999999,
"CO2_sd": 0.09683552049221775,
"CO2_slp": 0.15798184497769227,
"C12": 984.3306964999999,
"C12_sd": 0.09626425898406533,
"C12_slp": 0.1568479280658279,
"C13": 10.732370575000001,
"C13_sd": 0.000733651718716026,
"C13_slp": 0.0007457044104302504,
"O17": 0.77485919525,
"O17_sd": 0.0006381489733478628,
"O17_slp": -0.00032163199721669346,
"O18": 4.061307247499999,
"O18_sd": 0.0006038512660363844,
"O18_slp": 0.0006815634458901812,
"NH3": 12.745961175,
"NH3_sd": 0.4807668507578745,
"NH3_slp": -1.0440158893188,
"dC13": -29.720341025000003,
"dC13_sd": 0.09419300619565346,
"dC13_slp": -0.13454599382645405,
"dO17": -3.8357486775,
"dO17_sd": 0.7658243307591981,
"dO17_slp": -0.5950952046825331,
"dO18": -12.140916375,
"dO18_sd": 0.13636244665865435,
"dO18_slp": -0.07630746304904867
}
}Applied Tank Measurement (ATM) Files
ATM (applied tank measurement) files are saved in the home/licor/logs/tga/tanks/events/<serial> directory. They are created manually (Figure 12‑45) when one or more tank measurements are actually used to update a TGA calibration, or under program control (Capturing a Tank Measurement).
{
"events": [ //The list of TM events used.
"TM0257 @ 15:42 Diffs: CO2=-0.1ppm \u03b4C13=0.93\u2030",
"TM0258 @ 15:43 Diffs: CO2=0.0ppm \u03b4C13=0.17\u2030"
],
"tga_cal": {//The TGA cal before being changed by this ATM
"sn": "TG25-01057",
"latest_atm": "ATM0100",
"Offset_Cal_C12": 2.8499671464940115,
"Offset_Cal_C13": 0.07463568343094369,
"Offset_Cal_O18": 0.019001373117769792,
"Offset_Cal_O17": -0.005281035583985035,
"C12_Span": 1.0134588381927159,
"C13_Span": 1.019549060440458,
"O18_Span": 1.0093372871121618,
"O17_Span": 0.9364494128364119
},
"spans": { //The new TGA spans (always present)
"C12": 1.013185180680767,
"C13": 1.0195958329492814,
"O18": 1.0095267746387697,
"O17": 0.9371846109860461
},
"offsets": {//The new TGA spans (only present for multi-TM calibrations)
"C12": 3.102881001341697,
"C13": 0.07296212684004466,
"O18": 0.017842448264632153,
"O17": -0.006202159560105282
},
"meas": { //TGA measurements of the tanks, extracted from the TM files
"C12": [
393.63955533333336,
984.4218803333334
],
"C13": [
4.296139016666666,
10.735643600000001
],
"O18": [
1.62573474,
4.062277316666667
],
"O17": [
0.3111086056666666,
0.7757438246666666
]
},
"tank": { //True values, extracted from the tank values in the TM files
"C12": [
393.7486,
984.3714
],
"C13": [
4.2932,
10.733
],
"O18": [
1.6247,
4.0617
],
"O17": [
0.3101,
0.7751
]
},
"labels": { //Prompts used for the Implement? dialog.
"C12": "Set C12 span to 1.013185, offset to 3.102881",
"C13": "Set C13 span to 1.019596, offset to 0.072962",
"O18": "Set O18 span to 1.009527, offset to 0.017842",
"O17": "Set O17 span to 0.937185, offset to -0.006202"
},
"action_list": { //Check box settings from the Implement? dialog
"C12": true,
"C13": true,
"O18": true,
"O17": true
}, //Used for the dialog, if any
"header_text": "TM0257 @ 400 Diffs: CO2=-0.1ppm \u03b4C13=0.93\u2030, \u03b4O18=0.82\u2030\nTM0258 @ 1000
Diffs: CO2=0.0ppm \u03b4C13=0.17\u2
}