Notes for 2014 518 Laboratory.
Brian Hornbuckle, bkh@iastate.edu
April 13, 2014. Updated April 20, 2014.
Pre–laboratory Experiment
Here I present results from the pre–laboratory experiment that Matt Nelson and I performed
on April 8 in preparation for the two laboratories. The raw data is available on the syllabus
if you would like to use this to verify that you are performing your calculations correctly.
• NE∆T using the period of the first LN2 (liquid nitrogen) calibration: 0.8 K (calibration A); 0.9 K (calibration B).
• mystery temperature: 293 K = 20 ◦ C (calibration A); 295 K = 22 ◦ C (calibration B).
Actual measured temperature of water bath was 29 ◦ C, but it was measured with an
infrared thermometer, so likely not accurate.
• Trec = absolute value of y–intercept of calibration line: 381 K (calibration A); 474 K
(calibration B).
• gain or slope of calibration line: 4.43 × 103
(calibration B).
K
rQ units
(calibration A); 5.05 × 103
K
rQ units
Notes
Use the m–file read_float_binary.m to import the data from the laboratory into MATLAB
using the following syntax:
rQ = read_float_binary(’filename’);
where rQ is the variable in which you would like to place the data and filename will be, for
example, tpr_2014.04.10.13.42.23.dat. I created a “dummy” time vector in this way:
time = (1:length(rQ_data))./1e3;
I examined the data from both laboratories and the data from April 11 (the second laboratory) looks problematic. See Figure 4. If I remember correctly, the lid of the box holding
the radiometer electronics was off during the first laboratory, and on during the second.
Having the lid on or off seems to induce different radiation environments. I recommend that
those in the second laboratory use the data from the first laboratory.
1
0.2
0.18
0.16
rQ value
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
16
16.5
17
18
18.5
0.18
0.11
rQ value
17.5
0.105
19
0.175
0.155
0.1
0.17
0.15
0.165
0.145
LN2 cal A
17
17.2
17.4
0.16
18.2
18.4
18.6
mystery
18.8
0.18
0.115
LN2 cal B
0.11
0.17
0.165
0.1
19.15 19.2 19.25 19.3 19.35
H2O cal B
0.175
0.105
0.16
19.5
20
0.16
H20 cal A
0.095
0.09
16.8
19.5
19.6
19.7
time (data point/1000)
Figure 1: Data from the pre–laboratory experiment.
2
18.9
19
600
mA = 4429.3969 bA = −380.8599
m = 5050.7683 b = −473.6959
B
B
400
200
0
−200
−400
−600
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
Figure 2: Calibrations A and B from the pre–laboratory experiment.
3
0.2
400
calibration A
calibration B
350
brightness temperature, K
300
250
200
150
100
50
0
16
16.5
17
17.5
18
18.5
time (data point/1000)
19
19.5
20
Figure 3: Calibrated brightness temperature during the pre–laboratory experiment.
4
0.25
April 10
rQ value
0.2
0.15
0.1
0.05
0
15
15.5
16
16.5
17
17.5
18
18.5
19
0.25
April 11
rQ value
0.2
0.15
0.1
0.05
0
15
15.5
16
16.5
17
17.5
time (data point/1000)
18
18.5
Figure 4: Raw data from the first and second laboratories.
5
19