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Hi,
I am trying to test the Python API buffer mode, by plugging the mooshimeter (V and C plugs) into a 230V 50Hz ac signal. Settings used are: [Sampling frequency: 1kHz, Buffer depth: 256, Voltage range: 600V]
In all the buffers I get, the values are all positive. A typical buffer is shown below:
Received voltage buffer: [12, 33, 52, 66, 72, 72, 66, 51, 32, 10, 243, 222, 203, 189, 183, 183, 189, 204, 223, 245, 12, 34, 52, 66, 72, 72, 65, 51, 32, 10, 242, 221, 202, 189, 183, 183, 190, 204, 223, 246, 13, 34, 53, 66, 72, 72, 65, 50, 31, 9, 242, 221, 202, 188, 183, 183, 190, 205, 224, 246, 14, 35, 53, 67, 72, 72, 65, 50, 31, 8, 241, 220, 201, 188, 183, 183, 190, 205, 225, 247, 14, 35, 54, 67, 72, 72, 64, 49, 30, 8, 241, 220, 201, 188, 183, 183, 191, 206, 225, 248, 15, 36, 54, 67, 72, 72, 64, 49, 30, 7, 240, 219, 200, 188, 183, 183, 191, 206, 226, 248, 15, 36, 55, 67, 72, 72, 64, 48, 29, 6, 239, 218, 200, 188, 183, 183, 191, 207, 226, 249, 16, 37, 55, 68, 72, 72, 63, 48, 28, 6, 239, 218, 199, 187, 183, 183, 192, 207, 227, 249, 17, 37, 56, 68, 72, 72, 63, 48, 28, 5, 238, 217, 199, 187, 183, 183, 192, 208, 227, 250, 17, 38, 56, 68, 72, 72, 63, 47, 27, 4, 237, 217, 199, 187, 183, 183, 193, 208, 228, 251, 18, 38, 57, 68, 72, 71, 62, 46, 27, 4, 237, 216, 198, 187, 183, 184, 193, 209, 229, 252, 19, 39, 57, 68, 72, 71, 62, 46, 26, 3, 236, 216, 198, 187, 183, 184, 193, 209, 229, 252, 19, 40, 58, 69, 72, 71, 62, 46, 25, 3, 236, 215, 197, 186, 183, 184]
Looks like for the (expected) negative values, it is wrapping around at 255 as unsigned ints. Am I right? Also, the BUF_BPS parameter is shown as 8, which then makes sense. However, isn’t the BUF_BPS always expected to be 24 (wiki) ?
The LSB2Native factor at CH2 = 4.301601, which seems about right for the lower (non-wrapped) values in the buffer.
Also, how is the REAL_PWR parameter calculated? The calculation step given in the wiki seems to indicate that longer buffers will lead to larger powers, and also the units would become sqrt(W). :
This node provides the real power (as opposed to apparent power) measured during the last sample. The real power is calculated by multiplying every value in the channel 1 buffer by its counterpart in the channel 2 buffer, summing those results and square rooting the sum.
