Calculating transducer impedance with WBT
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The first 16–bits represent current measurements. |
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The next 16–bits represent voltage measurements. |
By adding zeros to the last 16–bit, mantissa bits, two float values can be obtained. Each complex sample will in this way be split into a complex current value and a complex voltage value, ready to be used for
calculation of transducer impedance.
These special format values are outputted as long as one of the WBT channels are transmitting. The number of values to be used for impedance calculation must be based on the information in the Filter XML datagrams and
the pulse duration.
Number of samples to remove before starting to calculate the transducer impedance in BITE:
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N1 = Stage1 filter NoOfCoefficients |
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N2 = Stage2 filter NoOfCoefficients in Stage2 |
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D1 = Stage1 filter DecimationFactor |
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D2 = Stage2 filter DecimationFactor |
NoOfCoefficients is an element in the Filter binary datagram.
DecimationFactor is an element in the Filter XML datagram.
Calculating total filter delay use this formula:
Total filter delay = (N1/2/D1 + N2/2) / D2
The calculation is valid for the start sample and the number of samples within the pulse duration.
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For Frequency Modulated (FM) pulse formats the raw files include a certain number of extra samples. These extra samples must be removed, before calculating the transducer impedance. |
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For signals using Continuous Wave (CW) pulse format, the raw file recordings does not include extra samples. These have been removed before data was stored in raw files. You do not have to remove any additional samples. |
WBT/EK80 sample data
Sample format from WBT during Tx/Rx
The sample data format for WBT is not the same during transmission and reception. The following to sections describe what the sample data looks like during these two functions.
Each sample data consists of a 32–bit section. This section consists of two 16–bit subsections.
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The first 16–bits represent current measurements. |
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The next 16–bits represent voltage measurements. |
Transmission
During transmission the sample data contains current and voltage data infomration. The current and voltage sample data are comprised by two parts, the real and imaginary part. The real part of both current and voltage is found in the first 32–bit field. The imaginary part of current and voltage is found in the second 32–bit field.
The first 32–bits:
| Current real part |
Voltage real part |
| S |
e |
e |
e |
e |
e |
e |
e |
e |
m |
m |
m |
m |
m |
m |
m |
S |
e |
e |
e |
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e |
e |
e |
e |
m |
m |
m |
m |
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m |
The second 32–bits:
| Current imaginary part |
Voltage imaginary part |
| S |
e |
e |
e |
e |
e |
e |
e |
e |
m |
m |
m |
m |
m |
m |
m |
S |
e |
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e |
e |
e |
e |
e |
m |
m |
m |
m |
m |
m |
m |
Reception
During reception the sample data contains high and low voltage gain data information. The high and low voltage gain data are comprised by two parts, the real and the imaginary part. The real part of both high and low voltage gain is comprised in the first 32–bit field. The imaginary part of high and low voltage is found in the second 32–bit field.
The first 32–bits:
| Voltage High Gain real part |
Voltage Low Gain real part |
| S |
e |
e |
e |
e |
e |
e |
e |
e |
m |
m |
m |
m |
m |
m |
m |
S |
e |
e |
e |
e |
e |
e |
e |
e |
m |
m |
m |
m |
m |
m |
m |
The second 32–bits:
| Voltage High Gain imaginary part |
Voltage Low Gain imaginary part |
| S |
e |
e |
e |
e |
e |
e |
e |
e |
m |
m |
m |
m |
m |
m |
m |
S |
e |
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e |
e |
e |
e |
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m |
m |
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m |
m |
Sample range for current/voltage samples
The number of current/voltage samples made during transmission is calculated. The base of this calculation is the maximum value of the pulse length, filter length and any pulse delay.
The maximum pulse duration for the different types of WBTs are:
Selection of high/low gain samples
The gain selector is a tool used to select sample voltage level selection. Low gain is automatically selected for all values when the low gain voltage exceeds 3 mV (RMS value).
Both the selected and the not selected gain are sent/saved. Tools like oscilloscope view and reprocessing the gain selected in replay.
From EK80 v.1.10.1 re-selection of gain during replay is default.
Transmission
The first 32–bits:
| Voltage real part |
Current real part |
| S |
e |
e |
e |
e |
e |
e |
e |
e |
m |
m |
m |
m |
m |
m |
m |
S |
e |
e |
e |
e |
e |
e |
e |
e |
m |
m |
m |
m |
m |
m |
m |
The second 32–bits:
| Voltage imaginary part |
Current imaginary part |
| S |
e |
e |
e |
e |
e |
e |
e |
e |
m |
m |
m |
m |
m |
m |
m |
S |
e |
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m |
m |
m |
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m |
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m |
Reception
The first 32–bits:
| Selected real part |
The other real part |
| S |
e |
e |
e |
e |
e |
e |
e |
e |
m |
m |
m |
m |
m |
m |
m |
S |
e |
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m |
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The second 32–bits:
| Selected imaginary part |
The other imaginary part |
| S |
e |
e |
e |
e |
e |
e |
e |
e |
m |
m |
m |
m |
m |
m |
m |
S |
e |
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m |
m |
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m |
m |
m |
X |
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X: This last bit in the imaginary value is telling what type of gain has been selected. 1 represents high gain, 0 represents low gain.
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Raw data content
The raw data files contain all samples, on this format after selection of gain chain.
From EK80 v.1.10.1 (20161122) gain is reselected by default during replay.