Remove crappy data from the beginning of log-locked

Add script to make a histogram.
Looks pretty good: 93% of points are within ±5mA (14 bits)
99.9% of points are within ±10mA (13 bits)


git-svn-id: https://bucket.mit.edu/svn/nilm/zoom@8115 ddd99763-3ecb-0310-9145-efcb8ce7c51f

pc/data/20091104/makehist.m

@@ -0,0 +1,14 @@
+a=load("log-locked");
+len=size(a,1)
+keith=a(:,3);
+calib=a(1,4)
+dac=a(:,5);
+adc=a(:,6);
+lookup=load("../../../firmware/lookup.inc");
+meas=-(lookup(dac + 1)/64 - calib * adc);
+keith_amps = keith * 50;         # 50 turns
+p = polyfit(meas, keith_amps, 1)
+meas_amps = meas * p(1) + p(2);  # calibration fit
+err_amps = keith_amps - meas_amps;
+
+[n, x] = hist(err_amps*1000, [-15:0.5:15], 1);

pc/data/20091104/process.txt

@@ -1,6 +1,6 @@
 Some processing thoughts:
 
-grep ^1 log | tail -n +125 > log-locked
+zcat log.gz | grep ^1 | tail -n +200000 > log-locked
 
 octave:
 
@@ -9,20 +9,20 @@ octave:
   t=1:10000;
   keith=a(:,3);
   calib=a(1,4)
-
   dac=a(:,5);
   adc=a(:,6);
   meas=-(dac - calib * adc);
-  plot(keith(t),meas(t))
-  p = polyfit(keith, meas, 1)
+  plot(keith(t),meas(t))   # should be linear
+
+  p = polyfit(keith, meas, 1)
+  plot(t,keith(t) * p(1) + p(2),t,meas(t))   # should match
 
-  plot(t,keith(t) * p(1) + p(2),t,meas(t))
   t=1:len;
-  plot(t,keith(t) * p(1) + p(2) - meas(t))
+  plot(t,keith(t) * p(1) + p(2) - meas(t))   # absolute error (units=dac)
   axis([0 len -1 1])
 
 Range is something like +- 0.5 over the entire range (of "DAC values")
-This gives log(1024 / 0.5) / log(2) = 11 bits
+This gives log(1024 / 1.0) / log(2) = 10 bits
 No good!
 Now let's convert the DAC values to their more-accurate value using the lookup table
 
@@ -31,10 +31,11 @@ Now let's convert the DAC values to their more-accurate value using the lookup t
   meas=-(lookup(dac + 1)/64 - calib * adc);
   p = polyfit(keith, meas, 1)
   t=1:len;
-  plot(t,keith(t) * p(1) + p(2) - meas(t))
+
+  plot(t,keith(t) * p(1) + p(2) - meas(t))   # absolute error (units=dac)
   axis([0 len -0.3 0.3])
 
-Now closer to +- 0.1
+Now closer to +- 0.05
 This gives log(1024 / 0.1) / log(2) = 13.3 bits