- #1
lcr2139
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Hello, I would like to measure power from a photodiode. How do I go about doing this? What would the circuit look like?
How to Measure Power Using a Photodiode?
- Thread starter lcr2139
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- Measure Photodiode Power
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Discussion Overview
The discussion centers around measuring power using a photodiode, particularly in the context of lasers. Participants explore circuit designs, measurement techniques, and the necessary information for accurate power measurement.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant inquires about the general method for measuring power from a photodiode and requests a circuit diagram.
- Another participant specifies the context of measuring power from a laser using a photodiode.
- A proposed circuit involves a current-to-voltage converter with an op-amp, which is shared via a link to an external image.
- It is noted that the circuit operates the LED as a photodiode at zero voltage to measure short circuit current, which correlates to photon flux. Calibration and knowledge of the photon wavelength are emphasized as necessary for converting current to power.
- One participant mentions successfully connecting a photodiode to an oscilloscope and seeks advice on measuring noise or signal-to-noise ratio (SNR), considering the use of an optical spectrum analyzer.
- A later reply expresses frustration over the lack of responses to questions about the specifics of the measurement setup, reiterating the need for additional information to provide better answers.
Areas of Agreement / Disagreement
Participants express a need for more information to provide accurate guidance, indicating a lack of consensus on the specifics of the measurement process and the circuit design.
Contextual Notes
Participants highlight the importance of knowing the laser's wavelength, power supply, and the type of photodiode used, suggesting that these factors significantly influence the measurement approach.
- #2
lcr2139
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I would like to measure the power of a laser through a photodiode, i mean.
- #3
berkeman
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The traditional circuit is a current-to-voltage converter with an opamp:lcr2139 said:
http://i.stack.imgur.com/hgwKe.gif
- #4
Baluncore
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The circuit given above operates the LED as a photodiode at zero voltage and so measures the short circuit current. Short circuit current is a measure of the flux of photons being received. That current can be converted to power if the wavelength (colour) of the photons is known. You will need to calibrate the system. You may need to use an optical attenuator for higher output lasers.
For better answers more information is needed.
Why do you want to measure the power ?
What is the laser wavelength or colour ?
What is the power supply for the laser ?
Does the laser have a manufacturers part number ?
What sort of photodiode did you plan to use ?
For better answers more information is needed.
Why do you want to measure the power ?
What is the laser wavelength or colour ?
What is the power supply for the laser ?
Does the laser have a manufacturers part number ?
What sort of photodiode did you plan to use ?
- #5
lcr2139
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I successfully hooked up my photodiode to an oscilloscope and got a good reading. Is there a way to measure noise, or SNR?
- #6
lcr2139
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lcr2139 said:
or should i use an optical spectrum analyzer?
- #7
Baluncore
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I am not a mind reader. Why do you not answer questions?
What type of laser are you using?Baluncore said:
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