Current sensor transfer impedance determination method: Difference between revisions

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{{note|This method is not a replacement for a real calibration.}}
= Theory =
[[Image:Current sensor Transfer impedance Prove.PNG]]
 
The left impedance is the signal generator which is generating enough power for 1 ampere.
 
This 1Amp. generates <math>P = I^2*R=50 \ Watt</math> in the right impedance.
 
The current sensor has 1 ohm transfer impedance, this means 1 ampere generates 1 Volt on the measuring part below.
 
The power in the lower 50 ohm impedance is <math>P = \frac{U^2}{R} = 20 \ mWatt</math>
 
So 1 ohm: <math>10*^{10}log(\frac{0,02}{50}) \approx -33,98 dB = -20*^{10}log(50)</math>
 
= Reference measurement =
[[Image:Current sensor Transfer impedance Ref measurement.PNG]]
 
= Probe measurement =
[[Image:Current sensor Transfer impedance final measurement.PNG]]
 
= Calculation =
<Math>Correction \ factor (dB)= P_{Measured} - P_{Reference}+ 33.98</Math>
 
<Math>P_{Measured}</Math> and <Math>P_{Reference}</Math> in dBm.
 
 
= Example =
On 10 MHz we have the following information:
*Calibration: 0 dBm.
*Measurement: -27,96 dBm.
 
So:
<math>Imp.=-27,96-0.00+33.98=6,02 dBOhm</math>
 
<math>Imp.\approx 2 \ Ohm</math>
 
== Verification ==
 
[[Image:Current sensor Transfer impedance example.png]]
 
The left impedance is the signal generator which is generating enough power for 1 ampere.
 
This 1 Ampere generates <math>P = I^2*R=50 \ Watt</math> in the right impedance.
 
The current sensor has 2 ohm transfer impedance, this means 1 ampere generates 2 Volt on the measuring part below.
 
The power in the lower 50 ohm impedance is <math>P = \frac{U^2}{R} = 80 \ mWatt</math>
 
So 2 ohm: <math>10*^{10}log(\frac{0,08}{50}) \approx -27,96 dB</math>
 
The difference to a 1 Ohm impedance is <math>-27,96 - (-33,98) = 6,02 dB</math>
 
==Conclusion==
 
Correction to a 1 ohm impedance is <math>20*^{10}log(R_{probe})</math>
 
 
{{note|This method is not a replacement for a real calibration as it may be performed by a none traceable device}}
 
[[Category:RadiMation]]

Latest revision as of 07:47, 31 July 2014

Theory[edit]

Current sensor Transfer impedance Prove.PNG

The left impedance is the signal generator which is generating enough power for 1 ampere.

This 1Amp. generates Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle P = I^2*R=50 \ Watt} in the right impedance.

The current sensor has 1 ohm transfer impedance, this means 1 ampere generates 1 Volt on the measuring part below.

The power in the lower 50 ohm impedance is Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle P = \frac{U^2}{R} = 20 \ mWatt}

So 1 ohm: Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 10*^{10}log(\frac{0,02}{50}) \approx -33,98 dB = -20*^{10}log(50)}

Reference measurement[edit]

Current sensor Transfer impedance Ref measurement.PNG

Probe measurement[edit]

Current sensor Transfer impedance final measurement.PNG

Calculation[edit]

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle Correction \ factor (dB)= P_{Measured} - P_{Reference}+ 33.98}

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle P_{Measured}} and Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle P_{Reference}} in dBm.


Example[edit]

On 10 MHz we have the following information:

  • Calibration: 0 dBm.
  • Measurement: -27,96 dBm.

So: Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle Imp.=-27,96-0.00+33.98=6,02 dBOhm}

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle Imp.\approx 2 \ Ohm}

Verification[edit]

Current sensor Transfer impedance example.png

The left impedance is the signal generator which is generating enough power for 1 ampere.

This 1 Ampere generates Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle P = I^2*R=50 \ Watt} in the right impedance.

The current sensor has 2 ohm transfer impedance, this means 1 ampere generates 2 Volt on the measuring part below.

The power in the lower 50 ohm impedance is Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle P = \frac{U^2}{R} = 80 \ mWatt}

So 2 ohm: Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 10*^{10}log(\frac{0,08}{50}) \approx -27,96 dB}

The difference to a 1 Ohm impedance is Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle -27,96 - (-33,98) = 6,02 dB}

Conclusion[edit]

Correction to a 1 ohm impedance is Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 20*^{10}log(R_{probe})}


Information.png
 Note: This method is not a replacement for a real calibration as it may be performed by a none traceable device

Power expressed in milliWatt in dB values.

  • 1 mW = 0 dBm
  • 2 mW = 3 dBm
  • 100 mW = 20 dBm
  • 1 W = 30 dBm
  • 100 W = 50 dBm

Resistance expressed in Ohm in dB values.

  • 1 Ohm = 0 dBOhm
  • 2 Ohm = 6 dBOhm
  • 10 Ohm = 20 dBOhm
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