ASCII Calibration

The internal ASCII calibration format is a simple ASCII format meant to be used when no other format is available. Each file only contains one set of calibration data (no chopper on or off) and there is no provision for different chopper on and off files.

The units of the internal format ASCII calibration files are interpreted to be:

  • Frequency in Hz

  • Magnitude in mV/nT

  • Phase in degrees or radians depending on the “Phase unit” header

Resistics will automatically convert these units to:

  • Frequency in Hz

  • Magnitude in mV/nT (including any static gain)

  • Phase in radians

Naming in the project environment

When using the project environment, resistics automatically searches for calibration files in the calData folder. Internal format ASCII files should be named according to the following specification:

Important

[*]IC_[SERIAL].txt

where,

  • SERIAL is the sensor serial number

  • [*] represents any general string

As an example, consider an induction coil with:

  • sensor serial number 307

Then the file should be named:

  • IC_307.TXT

  • Or with any leading text, e.g. magcal_IC_307.TXT

As can be seen, there is no ability to distinguish different sensors with the same serial number or situations where chopper is on or off. For those cases, RSP or Metronix formats are better.

Example

The internal ASCII format calibration file will not usually be provided and will have to be created from scratch. The CalibrationIO class provides the handy writeInternalTemplate() method for producing a template internal ASCII format calibration file. A template can be made as follows:

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from datapaths import calPath, calImages
from resistics.calibrate.io import CalibrationIO

# we can write a template into which to paste our data
writepath = calPath / "ascii.txt"
calIO = CalibrationIO()
calIO.writeInternalTemplate(writepath, 307, "MFS06", 1)

This produces an empty calibration file with some basic information in:

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Serial = 307
Sensor = MFS06
Static gain = 1
Magnitude unit = mV/nT
Phase unit = degrees
Chopper = False

CALIBRATION DATA

The basic metadata can either be corrected in the file or passed as keywords to writeInternalTemplate(). The actual calibration data needs to be copied in and should be in the units:

  • Magnitude in mV/nT without static gain

  • Phase in units which match the “Phase unit” header, which can either be degrees or radians

An example file with calibration data copied is provided below.

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Serial = 307
Sensor = MFS06
Static gain = 1
Magnitude unit = mV/nT
Phase unit = radians
Chopper = False

CALIBRATION DATA
+1.0000e-01  +1.9967e+01  +1.5452e+00
+1.4678e-01  +2.9303e+01  +1.5339e+00
+2.1544e-01  +4.2933e+01  +1.5173e+00
+3.1623e-01  +6.2901e+01  +1.4931e+00
+4.6416e-01  +9.1945e+01  +1.4576e+00
+6.8130e-01  +1.3418e+02  +1.4051e+00
+1.0000e+00  +1.9404e+02  +1.3394e+00
+1.4678e+00  +2.7551e+02  +1.2296e+00
+2.1544e+00  +3.8111e+02  +1.0904e+00
+3.1623e+00  +5.0078e+02  +9.1815e-01
+4.6416e+00  +6.1636e+02  +7.2902e-01
+6.8130e+00  +7.0664e+02  +5.4810e-01
+1.0000e+01  +7.6400e+02  +3.9286e-01
+1.4678e+01  +7.9669e+02  +2.7489e-01
+2.1545e+01  +8.1231e+02  +1.8837e-01
+3.1623e+01  +8.2062e+02  +1.2735e-01
+4.6416e+01  +8.2453e+02  +8.4177e-02
+6.8130e+01  +8.2219e+02  +4.5146e-02
+1.0000e+02  +8.2609e+02  +2.8629e-02
+1.4678e+02  +8.2567e+02  +1.0910e-02
+2.1545e+02  +8.2660e+02  -7.6749e-03
+3.1623e+02  +8.2631e+02  -2.6356e-02
+4.6417e+02  +8.2636e+02  -4.8977e-02
+6.8130e+02  +8.2730e+02  -7.8009e-02
+1.0000e+03  +8.2795e+02  -1.2135e-01
+1.4678e+03  +8.2721e+02  -1.8637e-01
+2.1545e+03  +8.1548e+02  -2.8374e-01
+3.1623e+03  +7.9639e+02  -4.2317e-01
+4.6417e+03  +7.1928e+02  -6.2696e-01
+6.8130e+03  +6.1971e+02  -7.4339e-01
+1.0000e+04  +5.7145e+02  -9.7107e-01

This internal format ASCII calibration file can now be read in using the CalibrationIO class. First, the reading parameters need to be reset using the refresh() method. Using the read() method will return a CalibrationData object.

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# read back the internal template file
filepath = calPath / "asciiWithData.txt"
calIO.refresh(filepath, "induction", extend=False)
calData = calIO.read()
calData.printInfo()

The printInfo() method prints information about the calibration data.

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15:15:46 CalibrationData: ####################
15:15:46 CalibrationData: CALIBRATIONDATA INFO BEGIN
15:15:46 CalibrationData: ####################
15:15:46 CalibrationData: Filename = calData\asciiWithData.txt
15:15:46 CalibrationData: Serial = 307
15:15:46 CalibrationData: Sensor = MFS06
15:15:46 CalibrationData: Static gain = 1.00
15:15:46 CalibrationData: Chopper = False
15:15:46 CalibrationData: Number of frequency points = 31
15:15:46 CalibrationData: Calibration data:
15:15:46 CalibrationData:          Frequency [Hz]       Mag. [mv/nT]    Phase [rad]
15:15:46 CalibrationData:              0.10000000            19.97            1.55
15:15:46 CalibrationData:              0.14678000            29.30            1.53
15:15:46 CalibrationData:              0.21544000            42.93            1.52
15:15:46 CalibrationData:              0.31623000            62.90            1.49
15:15:46 CalibrationData:              0.46416000            91.94            1.46
15:15:46 CalibrationData:              0.68130000           134.18            1.41
15:15:46 CalibrationData:              1.00000000           194.04            1.34
15:15:46 CalibrationData:              1.46780000           275.51            1.23
15:15:46 CalibrationData:              2.15440000           381.11            1.09
15:15:46 CalibrationData:              3.16230000           500.78            0.92
15:15:46 CalibrationData:              4.64160000           616.36            0.73
15:15:46 CalibrationData:              6.81300000           706.64            0.55
15:15:46 CalibrationData:             10.00000000           764.00            0.39
15:15:46 CalibrationData:             14.67800000           796.69            0.27
15:15:46 CalibrationData:             21.54500000           812.31            0.19
15:15:46 CalibrationData:             31.62300000           820.62            0.13
15:15:46 CalibrationData:             46.41600000           824.53            0.08
15:15:46 CalibrationData:             68.13000000           822.19            0.05
15:15:46 CalibrationData:            100.00000000           826.09            0.03
15:15:46 CalibrationData:            146.78000000           825.67            0.01
15:15:46 CalibrationData:            215.45000000           826.60           -0.01
15:15:46 CalibrationData:            316.23000000           826.31           -0.03
15:15:46 CalibrationData:            464.17000000           826.36           -0.05
15:15:46 CalibrationData:            681.30000000           827.30           -0.08
15:15:46 CalibrationData:           1000.00000000           827.95           -0.12
15:15:46 CalibrationData:           1467.80000000           827.21           -0.19
15:15:46 CalibrationData:           2154.50000000           815.48           -0.28
15:15:46 CalibrationData:           3162.30000000           796.39           -0.42
15:15:46 CalibrationData:           4641.70000000           719.28           -0.63
15:15:46 CalibrationData:           6813.00000000           619.71           -0.74
15:15:46 CalibrationData:          10000.00000000           571.45           -0.97
15:15:46 CalibrationData: ####################
15:15:46 CalibrationData: CALIBRATIONDATA INFO END
15:15:46 CalibrationData: ####################

To view the calibration data, the view() method of CalibrationData can be used. By passing a matplotlib figure to this, the layout of the plot can be controlled.

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# plot
import matplotlib.pyplot as plt

fig = plt.figure(figsize=(8, 8))
calData.view(fig=fig, label="Internal ASCII format", legend=True)
fig.tight_layout(rect=[0, 0.02, 1, 0.96])
plt.show()
fig.savefig(calImages / "calibrationASCII.png")

This produces the following plot:

alternate text

Viewing the unextended calibration data from the internal format ASCII file

Complete example script

For the purposes of clarity, the example script in full.

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from datapaths import calPath, calImages
from resistics.calibrate.io import CalibrationIO

# we can write a template into which to paste our data
writepath = calPath / "ascii.txt"
calIO = CalibrationIO()
calIO.writeInternalTemplate(writepath, 307, "MFS06", 1)

# read back the internal template file
filepath = calPath / "asciiWithData.txt"
calIO.refresh(filepath, "induction", extend=False)
calData = calIO.read()
calData.printInfo()

# plot
import matplotlib.pyplot as plt

fig = plt.figure(figsize=(8, 8))
calData.view(fig=fig, label="Internal ASCII format", legend=True)
fig.tight_layout(rect=[0, 0.02, 1, 0.96])
plt.show()
fig.savefig(calImages / "calibrationASCII.png")

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Serial = 307
Sensor = MFS06
Static gain = 1
Magnitude unit = mV/nT
Phase unit = radians
Chopper = False

CALIBRATION DATA
+1.0000e-01  +1.9967e+01  +1.5452e+00
+1.4678e-01  +2.9303e+01  +1.5339e+00
+2.1544e-01  +4.2933e+01  +1.5173e+00
+3.1623e-01  +6.2901e+01  +1.4931e+00
+4.6416e-01  +9.1945e+01  +1.4576e+00
+6.8130e-01  +1.3418e+02  +1.4051e+00
+1.0000e+00  +1.9404e+02  +1.3394e+00
+1.4678e+00  +2.7551e+02  +1.2296e+00
+2.1544e+00  +3.8111e+02  +1.0904e+00
+3.1623e+00  +5.0078e+02  +9.1815e-01
+4.6416e+00  +6.1636e+02  +7.2902e-01
+6.8130e+00  +7.0664e+02  +5.4810e-01
+1.0000e+01  +7.6400e+02  +3.9286e-01
+1.4678e+01  +7.9669e+02  +2.7489e-01
+2.1545e+01  +8.1231e+02  +1.8837e-01
+3.1623e+01  +8.2062e+02  +1.2735e-01
+4.6416e+01  +8.2453e+02  +8.4177e-02
+6.8130e+01  +8.2219e+02  +4.5146e-02
+1.0000e+02  +8.2609e+02  +2.8629e-02
+1.4678e+02  +8.2567e+02  +1.0910e-02
+2.1545e+02  +8.2660e+02  -7.6749e-03
+3.1623e+02  +8.2631e+02  -2.6356e-02
+4.6417e+02  +8.2636e+02  -4.8977e-02
+6.8130e+02  +8.2730e+02  -7.8009e-02
+1.0000e+03  +8.2795e+02  -1.2135e-01
+1.4678e+03  +8.2721e+02  -1.8637e-01
+2.1545e+03  +8.1548e+02  -2.8374e-01
+3.1623e+03  +7.9639e+02  -4.2317e-01
+4.6417e+03  +7.1928e+02  -6.2696e-01
+6.8130e+03  +6.1971e+02  -7.4339e-01
+1.0000e+04  +5.7145e+02  -9.7107e-01