impedanceTransformation

ET Typeobject 4.3.0

The impedanceTransformation object describes an eddy current impedance dataset transformation process.

Property	Type	Unit	Description
realGain required	number	dB	Gain applied to the real part of the recorded signal for all channels
imaginaryGain required	number	dB	Gain applied to the imaginary part of the recorded signal for all channels
rotation required	number	°	Rotation (phase angle) applied to the recorded signal
channels	array	-	A channels array with per-channel gain and rotation values from normalization

channels

ET Typearray 4.3.0

The channels array stores the normalization information for each individual channel of an eddy current probe. Real and imaginary gains are equal per channel, so only one gain value is stored.

Property	Type	Unit	Description
id required	number	-	Unique id of the channel
gain required	number	dB	Gain value used for normalization
rotation required	number	°	Rotation value used for normalization

Normalization

The primary goal of normalization is to uniformize the sensitivity across all ECA probe channels within a given group. The operator typically scans a reference sample containing a discontinuity engineered to produce a uniform response across all channels (e.g. a long transverse notch or a uniform lift-off variation). The gain and phase rotation of each channel are then adjusted to ensure consistent amplitude and phase responses across all channels.

Transformation order

Channel rotation and gain should be applied before group rotation and gains, as shown in the process workflow below.

flowchart TB
  raw[Raw signal from dataset]:::root --> rotation_channel_1["Channel 1 Rotation"]:::dataset
  raw --> rotation_channel_2["Channel 2 Rotation"]:::dataset
  rotation_channel_1 --> gain_channel_1["Channel 1 Gain"]:::dataset
  gain_channel_1 --> rotation_group["Group Rotation"]:::dataset
  rotation_channel_2 --> gain_channel_2["Channel 2 Gain"]:::dataset
  gain_channel_2 --> rotation_group
  rotation_group --> gain_imaginary_group["Group Imaginary Gain"]:::dataset
  rotation_group --> gain_real_group["Group Real Gain"]:::dataset
  gain_imaginary_group --> transformed["Transformed signal"]:::group
  gain_real_group --> transformed
  classDef root fill:#dcddde,stroke:#000000,color:#000000
  classDef group fill:#ffc72c,stroke:#000000,color:#000000
  classDef dataset fill:#fff,stroke:#000000,color:#000000 

Example

"impedanceTransformation": {
    "realGain": 13.420000000000002,
    "imaginaryGain": 13.420000000000002,
    "rotation": 80,
    "channels": [
        {
        "id": 0,
        "gain": 0.0,
        "rotation": 0.0
        },
        {
        "id": 1,
        "gain": 0.0,
        "rotation": 0.0
        }
    ]            
}