ATMS 748 Homework and Course Deliverables (return to main page)
[How to write lab report]
Title: Spatial variation of pressure, temperature, and relative humidity on the UNR Quad during an unsettled day, March 15.
The goals of this assignment is to explore the spatial variation of these quantities by using 6 sensor units equipped with temperature, RH, pressure, and GPS sensors.
Two of the sensors also have fast temperature measurements made possible through use of very small thermistors.
Each student will evaluate one 10 minute experiment and contribute to the presentation that will discuss results.
The question is, can we see relatively short range (10s or meters and 1 to 10s of seconds) variations in these meteorological parameters, given the sensor to sensor variations?
Over what length and time scales do we see variations if we do see them?
We acquired data for the UNR Quad turbulence experiment on the 15th of March. Here's the data from all the sensors.
Here are some notes on the set up from Karimar. Saroj notes with measurements and set up are here.
Here are some photos (the last one is from the day after, what a difference a day makes!):
Pressure Sensor (Transducer) MPX 4115 APand application note on how to filter the output
Temperature and humidity sensors made by Sensirion
Digital pressure sensor used on two of the boards MS5637.
Schematic and board layout, and the program for the Teensy microcontroller based package for sensors 10, 11, 12, and 13.
The board and sensors for the thermistor and digital pressure sensor are here, scroll down to the Perlan project for sensors 4 and 11 fast.
Title: Quantitative Generation and Measurement of Light with Arduinos, LEDs, and Photoresistors.
The goals of this assignment are:
a. Explore the use of photoresistors, LEDs and photodiodes as light detectors for applications.
b. Introduce a very common, and extremely useful device for measurements, the operational amplifier.
c. Show how you can get quantitative measurements from the Arduino microcontroller.
d. Reinforce the difference between ideal voltmeters and real voltmeters, that meter input resistance matters.
Measurements and Analysis
1. You have already done circuit 6, pg 40 in the book to learn about the photoresistor and how to measure its output.
We are going to add to that circuit.
Add a circuit to drive an LED to see if the photoresistor resistance can accurately follow the LED output for low and high frequencies.
Point the LED output directly into the photoresistor input. You can use variable delay and the 'Blink' sketch to drive the LED.
If the LED is driven by a square wave, the photoresistance should show a crisp square wave too. Use the plot monitor on Arduino to view the photoresistor output,
and save some data with CoolTerm (including time) so that you can graph the photoresistor output from the LED drive as a function of time.
Use Excel to obtain the time constant of the photoresistor as a sensor of light.
Here's an example sketch that may be helpful in measuring response time. You may find ways of speeding it up to get more time resolution on the LED response.
[Does photoresistor nonlinearity play a role in its frequency response?]
Description of the circuit for the photoresistor test. Click on the image for a larger version.
2. Build a simple circuit with a resistor and LED as a photodetector so that you can measure the photocurrent from the LED such that 0.1 microamps produces a 1 volt signal.
What resistance value are you going to need to 'program' the voltage output this way?
Construct transimpedance amplifier circuit with an op amp to convert the photocurrent from an LED as a light detector to a voltage so that a photocurrent of 0.1 microamps produces a 1 volt signal.
A. Write a sketch (or modify the sketch from part 1) for the Arduino to output relative time, and voltage from these circuits with as fast an update time at you can make.
You may need to increase the serial communication rate with the computer and write your code so that the Arduino makes efficient use of computing time .
Use a light source and rapidly shine it over the detectors.
Write your data to a file using CoolTerm.
Graph your time series. Compare the time response and noise of these circuits.
Board for the Op Amp lab. Click on image for larger version.
Photograph of the Arduino set up for this lab. Click on image for larger version.
3. Set up the non inverting amplifier circuit with a feedback resistor of 2k Ohm and 2.2uF capacitor in parallel, with a resistor of R1=10 MegOhm. Measure a pulse from the LED using the same Arduino program we used for testing the photoresistor. Show the effectiveness of shielding the circuit with aluminum foil. Photographs of the set up, and data, are available on the Daily Notes page.
4. Extra credit: One idea is to use the LEDs as detectors to estimate/measure cloud optical thickness.
[idea for additional project: measure the downwelling solar irradiance with both blue and red LEDs.
On a clear day the blue channel should receive more radiation than red compared with a cloudy day.]
Photodiode technical information sheet.
OSRAM BPW34 photodiode data sheet.
Discussion of operational amplifiers.
Use of light emitting diodes as wavelength specific radiation detectors,
as they are very useful for use in simple sun photometers, among other applications.
Description of the Arduino and some sensors we'll use.
Very useful voltage divider circuit to use for measuring sensors that depend on resistance.
Click on image for larger view.
Purpose: Gain an overview of atmospheric measurements. This assignment is given in webCampus.
Become familiar with the Arduino microcontroller, breadboarding circuits, and obtaining your own measurements with an analog to digital convertor.
Establish a common set of expectations for lab report writing.
Do all 12 projects in the Arduino guide book. There may be errors in the projects, as we'll find out as we go along..
I strongly recommend you install the Arduino software on your own laptop, and use it in class, if you have one.
The code for the projects is here: expand the file and put the folder in your Arduino examples folder.
Write a report about 3 of the experiments, temperature measurement, light measurement, and shift register control of 8 LEDs.
Your report needs to include the following (and see below for general reporting requirements):
What is the Arduino?
What is the principle of operation of the temperature sensor? How was its signal obtained?
What is the principle of operation of the light sensor? How was its signal obtained?
What is a shift register? How and why are they used?
Final open ended question: What would you like to do with the Arduino and appropriate hardware (you specify), if given the time and resources for development?
Description of the Arduino and some sensors we'll use.
|Description of the analog to digital conversion for the TMP36 sensor. Click on image for a larger version.
These notes are for attempting to increase the
resolution of the measurements.
EXPECTATIONS IN LAB REPORTS
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