Temperature Coefficient of Temperature Coefficient of Radiant - - PowerPoint PPT Presentation

Temperature Coefficient of Temperature Coefficient of Radiant Sensitivity of Silicon Radiant Sensitivity of Silicon Photodiodes for SIM Photodiodes for SIM

Presentation by: Presentation by: Brian Kirby Brian Kirby Mentors: Mentors: Jerry Harder Jerry Harder Erik Richard Erik Richard

Outline Outline

  Background on the SIM instrument

Background on the SIM instrument

  Radiant sensitivity and why it

Radiant sensitivity and why it’ ’s important s important

  Experiment

Experiment

  The setup

The setup

  How data was taken

How data was taken

  Results

Results

  The next steps

The next steps

  Summary

Summary

  Celebrate the end of presentations

Celebrate the end of presentations

Spectral Irradiance Monitor Spectral Irradiance Monitor

  SIM monitors the solar

SIM monitors the solar spectral variability spectral variability

  Scans the solar spectrum

Scans the solar spectrum 9-13 times a day 9-13 times a day

  This data is crucial in

This data is crucial in understanding: understanding:

  The Sun

The Sun

  Climate change on Earth

Climate change on Earth

SIM: What it does SIM: What it does

  Measures solar irradiance

Measures solar irradiance between 200 and 2700 nm between 200 and 2700 nm

  About 96% of total solar

About 96% of total solar irradiance irradiance

  Uses electrical

Uses electrical substitution radiometer as substitution radiometer as primary detector primary detector

  Incorporates four

Incorporates four additional photodiode additional photodiode detectors detectors

SIM: How It Works SIM: How It Works

  A prism and reference

A prism and reference mirror are controlled by mirror are controlled by a voice coil a voice coil

  The prism disperses the

The prism disperses the light into its different light into its different wavelengths on the wavelengths on the diodes diodes

  The mirror directs light

The mirror directs light

• nto the charged
• nto the charged

coupled device to sense coupled device to sense what wavelengths are what wavelengths are being measured being measured

Are You Paying Attention? Are You Paying Attention?

  What does SIM stand for?

What does SIM stand for?

  Spectral Irradiance Monitor

Spectral Irradiance Monitor

Scope of Project Scope of Project

Scope of this project

Radiant Sensitivity of Photodiodes Radiant Sensitivity of Photodiodes

  Ratio of output current to light power received

Ratio of output current to light power received

  Amps/watt

Amps/watt

  Function of wavelength and temperature

Function of wavelength and temperature

  Measured at all wavelengths at a controlled

Measured at all wavelengths at a controlled temperature temperature

  Scaled to the temperature of diodes at time of reading

Scaled to the temperature of diodes at time of reading

( ) ( ) ( )

1 1 1

, , 1 R T R T T T

• =

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• (

) ( ) ( ) ( )

, , 1

• R

T R T T T

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Radiant Sensitivity of SIM Diodes Radiant Sensitivity of SIM Diodes

  The radiant sensitivity curves are plotted against wavelengths

The radiant sensitivity curves are plotted against wavelengths bellow bellow

  These curves will scale if the temperature changes

These curves will scale if the temperature changes

  If not taken into account, the solar irradiance data will be wrong

If not taken into account, the solar irradiance data will be wrong

SORCE SIM Measured Temperatures (June 14, 2008) SORCE SIM Measured Temperatures (June 14, 2008)

SORCE SIM Temps

17 18 19 20 21 22 23 24 25 26 90 180 270 360 Time (min) Temp (C)

ESR CCD Pixel 12000 Diode, Vis1 Diode, Vis2 Diode, IR Diode, U V CCD Pixel 1 Case, front aperture Case, near focalplane Case, near center Case, near prism drive prism

  If not taken into

If not taken into account, these account, these temperature temperature changes could changes could cause false data cause false data that could be that could be mistaken for mistaken for changes in the changes in the solar irradiance solar irradiance

The Beta Angle The Beta Angle

Courtesy of NASA http://spaceflight.nasa.gov/station/flash/start.swf

Beta Angle Beta Angle’ ’s Effect on Temperature s Effect on Temperature

Are You Really Paying Attention? Are You Really Paying Attention?

  What is Radiant Sensitivity?

What is Radiant Sensitivity?

  Amps of output current/watt of power received

Amps of output current/watt of power received by the detector by the detector

Experiment to Measure Temperature Experiment to Measure Temperature Coefficient Coefficient

Simulate Sun With Lasers Split the Beam 50% 50% Control Photodiode Test Photodiode Constant intensity and wavelength Kept at room temperature. Temperature is monitored along with output voltage. Temperature is changed. Temperature is monitored along with

• utput voltage.

Pictures of Experiment Pictures of Experiment

Laser Driver Laser Driver

  Laser is kept at constant

Laser is kept at constant intensity and wavelength intensity and wavelength

  Thermoelectric cooler

Thermoelectric cooler keeps laser at a constant keeps laser at a constant temperature to maintain temperature to maintain consistent wavelength consistent wavelength

  Monitors laser output and

Monitors laser output and corrects current to corrects current to maintain constant maintain constant intensity intensity

Photodiode Mounts Photodiode Mounts

  Thermoelectric Coolers

Thermoelectric Coolers change temperature of change temperature of photodiode photodiode

  Operational amplifier

Operational amplifier allows us to easily allows us to easily monitor the monitor the photodiode photodiode’ ’s output s output voltage voltage

  Thermistors

Thermistors allow for us allow for us to monitor the to monitor the temperature of the temperature of the photodiode photodiode

Who Wants Candy? Who Wants Candy?

  To assure we

To assure we’ ’re monitoring how the radiant re monitoring how the radiant sensitivity changes at a specific wavelength sensitivity changes at a specific wavelength

  What is the purpose of enclosing the experiment

What is the purpose of enclosing the experiment in a box? in a box?

Gain Experiments Gain Experiments

  Tested the two

Tested the two photodiode circuit photodiode circuit boards for differences in boards for differences in gain values gain values

  Also tested how the gain

Also tested how the gain changed with changed with temperature temperature

Recording the Data Recording the Data

  LabView

LabView code monitors code monitors several channels on a several channels on a Keithley Keithley Multimeter Multimeter

  The data can be

The data can be monitored during the monitored during the experiment experiment

  The readings are also

The readings are also saved in a text file for saved in a text file for post experiment analysis post experiment analysis

LabView Virtual Interface LabView Block Diagram

Procedure for Taking Data Procedure for Taking Data

  Data was taken at 670nm, 830nm and 904nm

Data was taken at 670nm, 830nm and 904nm

  Each wavelength was tested at a range of

Each wavelength was tested at a range of temperatures temperatures

  Each temperature test lasted one hour

Each temperature test lasted one hour

  Before and after each test a baseline test was

Before and after each test a baseline test was conducted conducted

Procedure for Analyzing Data Procedure for Analyzing Data

  The data was imported into IDL

The data was imported into IDL

  Statistics were done on all experiments to verify good

Statistics were done on all experiments to verify good data was taken data was taken

  Baseline reading were taken into account

Baseline reading were taken into account

  The ratio of test diode output to the control diode

The ratio of test diode output to the control diode

• utput was graphed
• utput was graphed

  A line was fit to the data using a

A line was fit to the data using a bivariant bivariant least squares least squares fit method fit method

  This line is the temperature coefficient of radiant sensitivity

This line is the temperature coefficient of radiant sensitivity

Eliminating the Baseline Reading Eliminating the Baseline Reading

Results Results

The Next Steps The Next Steps

  Phased experiment needs to be created

Phased experiment needs to be created

  More wavelengths need to be measured

More wavelengths need to be measured

  The lasers need to be tested accurately

The lasers need to be tested accurately

Final Goal Final Goal

  The next SIM should be calibrated with a

The next SIM should be calibrated with a machine that works like this experiment machine that works like this experiment

  This calibration will

This calibration will accuratly accuratly find the find the temperature coefficient of radiant sensitivity for temperature coefficient of radiant sensitivity for all wavelengths measure by SIM all wavelengths measure by SIM

  Without this correction it will be impossible for

Without this correction it will be impossible for SIM to meet the required 0.01% accuracy SIM to meet the required 0.01% accuracy

Quick Summary Quick Summary

  SIM is designed to measures the solar spectrum

SIM is designed to measures the solar spectrum

  This data is crucial to understanding the Sun and

This data is crucial to understanding the Sun and it it’ ’s effect on Earth s effect on Earth’ ’s climate s climate

  This experiment was designed to help make the

This experiment was designed to help make the SIM data more accurate SIM data more accurate

It It’ ’s over! s over!

  Any Questions?

Any Questions?