Redwire 3-Phase Potential Transducer (PT12)

PT live PT revA

The PT12 measures 256 synchronized samples over a single cycle on four phases: 3 voltage phases and earth ground all with respect to neutral.

It is powered from phase A and rated to 277Vrms per phase.

Accuracy class: 0.3%

The PT12 receives a global ipv6 address via 6LoWPAN and POSTs data to servers on the internet at a configurable period.

The firmware is implemented with Contiki OS.

Below is a plot of data taken from the live 3-Phase and Earth ground at Redwire. We will be performing accuracy validation this August.

In [105]:
import pandas as pd
import matplotlib.pyplot as plt

df = pd.read_csv("pt-27690.csv",index_col=0, parse_dates=True)
df.plot()
Out[105]:
<matplotlib.axes.AxesSubplot at 0x4bb0dd0>
In [72]:
f = open("pt-27690.csv","r")
data = f.read()
f.close()
print data
,A,B,C,E
2013-07-24 13:21:47.075409,1579,2906.0,1694.0,2060.0
2013-07-24 13:21:47.075474,1554,2902.0,1717.0,2060.0
2013-07-24 13:21:47.075539,1537,2900.0,1742.0,2060.0
2013-07-24 13:21:47.075604,1526,2891.0,1763.0,2060.0
2013-07-24 13:21:47.075669,1505,2899.0,1786.0,2060.0
2013-07-24 13:21:47.075734,1486,2883.0,1797.0,2060.0
2013-07-24 13:21:47.075799,1478,2880.0,1820.0,2060.0
2013-07-24 13:21:47.075864,1463,2880.0,1846.0,2060.0
2013-07-24 13:21:47.075929,1447,2871.0,1864.0,2060.0
2013-07-24 13:21:47.075994,1434,2865.0,1887.0,2060.0
2013-07-24 13:21:47.076059,1418,2856.0,1906.0,2060.0
2013-07-24 13:21:47.076124,1406,2851.0,1931.0,2060.0
2013-07-24 13:21:47.076189,1392,2848.0,1946.0,2060.0
2013-07-24 13:21:47.076254,1384,2840.0,1965.0,2060.0
2013-07-24 13:21:47.076319,1370,2827.0,1985.0,2060.0
2013-07-24 13:21:47.076384,1354,2815.0,2008.0,2060.0
2013-07-24 13:21:47.076449,1354,2810.0,2034.0,2060.0
2013-07-24 13:21:47.076514,1334,2804.0,2058.0,2060.0
2013-07-24 13:21:47.076579,1321,2783.0,2065.0,2060.0
2013-07-24 13:21:47.076644,1313,2775.0,2093.0,2060.0
2013-07-24 13:21:47.076709,1308,2772.0,2118.0,2060.0
2013-07-24 13:21:47.076774,1298,2763.0,2135.0,2060.0
2013-07-24 13:21:47.076839,1288,2750.0,2156.0,2060.0
2013-07-24 13:21:47.076904,1280,2738.0,2173.0,2060.0
2013-07-24 13:21:47.076969,1272,2726.0,2188.0,2060.0
2013-07-24 13:21:47.077034,1265,2714.0,2207.0,2060.0
2013-07-24 13:21:47.077099,1258,2701.0,2231.0,2060.0
2013-07-24 13:21:47.077164,1253,2692.0,2254.0,2060.0
2013-07-24 13:21:47.077229,1248,2677.0,2268.0,2060.0
2013-07-24 13:21:47.077294,1242,2658.0,2286.0,2060.0
2013-07-24 13:21:47.077359,1237,2645.0,2308.0,2061.0
2013-07-24 13:21:47.077424,1233,2629.0,2328.0,2061.0
2013-07-24 13:21:47.077489,1228,2614.0,2347.0,2061.0
2013-07-24 13:21:47.077554,1225,2597.0,2368.0,2061.0
2013-07-24 13:21:47.077619,1222,2578.0,2388.0,2061.0
2013-07-24 13:21:47.077684,1218,2560.0,2406.0,2060.0
2013-07-24 13:21:47.077749,1216,2543.0,2426.0,2060.0
2013-07-24 13:21:47.077814,1214,2522.0,2444.0,2060.0
2013-07-24 13:21:47.077879,1212,2505.0,2465.0,2061.0
2013-07-24 13:21:47.077944,1211,2487.0,2483.0,2060.0
2013-07-24 13:21:47.078009,1210,2465.0,2497.0,2061.0
2013-07-24 13:21:47.078074,1210,2446.0,2514.0,2061.0
2013-07-24 13:21:47.078139,1210,2425.0,2530.0,2060.0
2013-07-24 13:21:47.078204,1210,2406.0,2547.0,2060.0
2013-07-24 13:21:47.078269,1210,2385.0,2558.0,2060.0
2013-07-24 13:21:47.078334,1212,2360.0,2570.0,2060.0
2013-07-24 13:21:47.078399,1214,2340.0,2589.0,2061.0
2013-07-24 13:21:47.078464,1216,2323.0,2609.0,2060.0
2013-07-24 13:21:47.078529,1218,2304.0,2626.0,2061.0
2013-07-24 13:21:47.078594,1222,2280.0,2635.0,2061.0
2013-07-24 13:21:47.078659,1226,2256.0,2649.0,2060.0
2013-07-24 13:21:47.078724,1232,2232.0,2660.0,2060.0
2013-07-24 13:21:47.078789,1236,2213.0,2667.0,2060.0
2013-07-24 13:21:47.078854,1242,2191.0,2683.0,2060.0
2013-07-24 13:21:47.078919,1252,2170.0,2699.0,2060.0
2013-07-24 13:21:47.078984,1260,2152.0,2715.0,2060.0
2013-07-24 13:21:47.079049,1276,2137.0,2730.0,2060.0
2013-07-24 13:21:47.079114,1288,2117.0,2742.0,2060.0
2013-07-24 13:21:47.079179,1297,2094.0,2762.0,2060.0
2013-07-24 13:21:47.079244,1305,2076.0,2777.0,2060.0
2013-07-24 13:21:47.079309,1318,2057.0,2780.0,2060.0
2013-07-24 13:21:47.079374,1328,2035.0,2796.0,2060.0
2013-07-24 13:21:47.079439,1334,2015.0,2798.0,2060.0
2013-07-24 13:21:47.079504,1346,1999.0,2811.0,2060.0
2013-07-24 13:21:47.079569,1357,1974.0,2821.0,2060.0
2013-07-24 13:21:47.079634,1368,1956.0,2828.0,2060.0
2013-07-24 13:21:47.079699,1379,1940.0,2838.0,2060.0
2013-07-24 13:21:47.079764,1390,1920.0,2843.0,2060.0
2013-07-24 13:21:47.079829,1402,1900.0,2854.0,2060.0
2013-07-24 13:21:47.079894,1415,1880.0,2861.0,2060.0
2013-07-24 13:21:47.079959,1425,1861.0,2861.0,2060.0
2013-07-24 13:21:47.080024,1438,1842.0,2871.0,2060.0
2013-07-24 13:21:47.080089,1454,1821.0,2869.0,2060.0
2013-07-24 13:21:47.080154,1470,1801.0,2881.0,2060.0
2013-07-24 13:21:47.080219,1484,1781.0,2882.0,2060.0
2013-07-24 13:21:47.080284,1502,1761.0,2887.0,2060.0
2013-07-24 13:21:47.080349,1520,1742.0,2895.0,2060.0
2013-07-24 13:21:47.080414,1536,1720.0,2889.0,2060.0
2013-07-24 13:21:47.080479,1553,1703.0,2903.0,2060.0
2013-07-24 13:21:47.080544,1572,1685.0,2895.0,2060.0
2013-07-24 13:21:47.080609,1590,1664.0,2901.0,2060.0
2013-07-24 13:21:47.080674,1610,1648.0,2904.0,2060.0
2013-07-24 13:21:47.080739,1631,1629.0,2903.0,2060.0
2013-07-24 13:21:47.080804,1650,1613.0,2911.0,2060.0
2013-07-24 13:21:47.080869,1670,1594.0,2902.0,2060.0
2013-07-24 13:21:47.080934,1692,1577.0,2906.0,2060.0
2013-07-24 13:21:47.080999,1712,1563.0,2902.0,2060.0
2013-07-24 13:21:47.081064,1732,1548.0,2899.0,2060.0
2013-07-24 13:21:47.081129,1755,1536.0,2896.0,2060.0
2013-07-24 13:21:47.081194,1773,1516.0,2892.0,2060.0
2013-07-24 13:21:47.081259,1795,1495.0,2891.0,2060.0
2013-07-24 13:21:47.081324,1816,1489.0,2891.0,2060.0
2013-07-24 13:21:47.081389,1837,1474.0,2878.0,2060.0
2013-07-24 13:21:47.081454,1857,1456.0,2877.0,2060.0
2013-07-24 13:21:47.081519,1876,1440.0,2867.0,2060.0
2013-07-24 13:21:47.081584,1899,1432.0,2859.0,2060.0
2013-07-24 13:21:47.081649,1920,1417.0,2853.0,2060.0
2013-07-24 13:21:47.081714,1942,1404.0,2843.0,2060.0
2013-07-24 13:21:47.081779,1961,1388.0,2841.0,2060.0
2013-07-24 13:21:47.081844,1982,1376.0,2828.0,2060.0
2013-07-24 13:21:47.081909,2006,1367.0,2822.0,2060.0
2013-07-24 13:21:47.081974,2028,1356.0,2809.0,2060.0
2013-07-24 13:21:47.082039,2047,1341.0,2807.0,2060.0
2013-07-24 13:21:47.082104,2066,1328.0,2786.0,2060.0
2013-07-24 13:21:47.082169,2088,1316.0,2779.0,2060.0
2013-07-24 13:21:47.082234,2106,1310.0,2777.0,2060.0
2013-07-24 13:21:47.082299,2126,1300.0,2759.0,2061.0
2013-07-24 13:21:47.082364,2148,1289.0,2747.0,2060.0
2013-07-24 13:21:47.082429,2166,1281.0,2741.0,2060.0
2013-07-24 13:21:47.082494,2183,1271.0,2727.0,2061.0
2013-07-24 13:21:47.082559,2203,1264.0,2713.0,2060.0
2013-07-24 13:21:47.082624,2225,1256.0,2707.0,2060.0
2013-07-24 13:21:47.082689,2243,1254.0,2694.0,2061.0
2013-07-24 13:21:47.082754,2262,1248.0,2671.0,2060.0
2013-07-24 13:21:47.082819,2282,1238.0,2655.0,2060.0
2013-07-24 13:21:47.082884,2302,1238.0,2646.0,2060.0
2013-07-24 13:21:47.082949,2321,1232.0,2631.0,2061.0
2013-07-24 13:21:47.083014,2343,1230.0,2620.0,2061.0
2013-07-24 13:21:47.083079,2363,1228.0,2603.0,2060.0
2013-07-24 13:21:47.083144,2382,1222.0,2583.0,2060.0
2013-07-24 13:21:47.083209,2401,1219.0,2567.0,2061.0
2013-07-24 13:21:47.083274,2422,1219.0,2551.0,2060.0
2013-07-24 13:21:47.083339,2441,1216.0,2530.0,2060.0
2013-07-24 13:21:47.083404,2460,1216.0,2514.0,2060.0
2013-07-24 13:21:47.083469,2479,1216.0,2496.0,2060.0
2013-07-24 13:21:47.083534,2498,1216.0,2478.0,2060.0
2013-07-24 13:21:47.083599,2516,1216.0,2458.0,2060.0
2013-07-24 13:21:47.083664,2534,1217.0,2438.0,2061.0
2013-07-24 13:21:47.083729,2555,1218.0,2410.0,2060.0
2013-07-24 13:21:47.083794,2565,1222.0,2400.0,2061.0
2013-07-24 13:21:47.083859,2582,1222.0,2379.0,2060.0
2013-07-24 13:21:47.083924,2601,1226.0,2356.0,2060.0
2013-07-24 13:21:47.083989,2616,1228.0,2337.0,2060.0
2013-07-24 13:21:47.084054,2630,1232.0,2317.0,2060.0
2013-07-24 13:21:47.084119,2644,1237.0,2297.0,2060.0
2013-07-24 13:21:47.084184,2659,1242.0,2276.0,2060.0
2013-07-24 13:21:47.084249,2673,1248.0,2255.0,2060.0
2013-07-24 13:21:47.084314,2688,1256.0,2238.0,2060.0
2013-07-24 13:21:47.084379,2701,1262.0,2216.0,2060.0
2013-07-24 13:21:47.084444,2714,1268.0,2194.0,2060.0
2013-07-24 13:21:47.084509,2725,1276.0,2171.0,2060.0
2013-07-24 13:21:47.084574,2738,1281.0,2153.0,2060.0
2013-07-24 13:21:47.084639,2751,1290.0,2135.0,2060.0
2013-07-24 13:21:47.084704,2765,1306.0,2113.0,2060.0
2013-07-24 13:21:47.084769,2768,1312.0,2088.0,2061.0
2013-07-24 13:21:47.084834,2787,1316.0,2061.0,2060.0
2013-07-24 13:21:47.084899,2801,1336.0,2053.0,2060.0
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2013-07-24 13:21:47.085029,2815,1352.0,1999.0,2060.0
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2013-07-24 13:21:47.085419,2863,1419.0,1889.0,2060.0
2013-07-24 13:21:47.085484,2869,1428.0,1866.0,2060.0
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2013-07-24 13:21:47.085679,2885,1478.0,1813.0,2060.0
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2013-07-24 13:21:47.090554,2016,2815.0,1354.0,2060.0
2013-07-24 13:21:47.090619,1994,2822.0,1358.0,2060.0
2013-07-24 13:21:47.090684,1972,2830.0,1366.0,2060.0
2013-07-24 13:21:47.090749,1953,2841.0,1380.0,2060.0
2013-07-24 13:21:47.090814,1937,2849.0,1392.0,2060.0
2013-07-24 13:21:47.090879,1916,2857.0,1408.0,2060.0
2013-07-24 13:21:47.090944,1897,2863.0,1420.0,2060.0
2013-07-24 13:21:47.091009,1877,2868.0,1432.0,2060.0
2013-07-24 13:21:47.091074,1858,2875.0,1448.0,2060.0
2013-07-24 13:21:47.091139,1838,2879.0,1464.0,2060.0
2013-07-24 13:21:47.091204,1818,2885.0,1474.0,2060.0
2013-07-24 13:21:47.091269,1798,2887.0,1487.0,2060.0
2013-07-24 13:21:47.091334,1774,2893.0,1508.0,2060.0
2013-07-24 13:21:47.091399,1758,2895.0,1515.0,2060.0
2013-07-24 13:21:47.091464,1736,2894.0,1532.0,2060.0
2013-07-24 13:21:47.091529,1717,2900.0,1553.0,2060.0
2013-07-24 13:21:47.091594,1698,2902.0,1570.0,2060.0
2013-07-24 13:21:47.091659,1678,2903.0,1588.0,2060.0
2013-07-24 13:21:47.091724,1658,2905.0,1610.0,2060.0
2013-07-24 13:21:47.091789,1640,2907.0,1628.0,2060.0
2013-07-24 13:21:47.091854,1622,2906.0,1646.0,2060.0
2013-07-24 13:21:47.091919,1604,2906.0,1665.0,2060.0
2013-07-24 13:21:47.091984,1586,2907.0,1684.0,2060.0

In [56]:
period = (df.index[-1] - df.index[0]).total_seconds()

print "%03f ms" % (period * 1000)
print "%03f Hz" % (1/period)
16.575000 ms
60.331825 Hz
In [ ]:
#theoretical offset is 15mV (12.288 codes). Measured offset is 12 codes.
# 1 code is 240mV in the primary voltage
In [104]:
mvLSB = 5 / float(2**12)
gain = 500/3.0
offset = 12

Vpp = {}
Vrms = {}

for p in ['A','B','C','E']:
    pmax = df[p].max() - offset
    pmin = df[p].min() - offset
    pp = pmax - pmin 
    
    Vpp[p]  = pp * mvLSB * gain
    Vrms[p] = Vpp[p] / (2 * sqrt(2))
    
print "A: %.1f Vpp , B: %.1f Vpp , C: %0.1f Vpp , E: %.1f Vpp" % (Vpp['A'], Vpp['B'], Vpp['C'], Vpp['E'])
print "A: %.1f Vrms, B: %.1f Vrms, C: %0.1f Vrms, E: %.1f Vrms" % (Vrms['A'], Vrms['B'], Vrms['C'], Vrms['E'])
    
A: 346.1 Vpp , B: 344.0 Vpp , C: 346.1 Vpp , E: 0.2 Vpp
A: 122.4 Vrms, B: 121.6 Vrms, C: 122.4 Vrms, E: 0.1 Vrms