Statistics API

The statistics API consists of the statistics data structure, which is provided periodically to registered callbacks. The data structure contains the following top-level keys:

• time: The time information which includes:

  • range: The (start, stop) time range for this data structure.

  • delta: The total duration which is equal to (stop - start).

  • samples: The total number of samples combined into this data.

• signals: The signal values over the previous statistics time window. The keys include current, voltage, and power. Each key contains a map with keys:

  • µ: The mean (average) value.

  • σ2: The variance value.

  • min: The minimum value.

  • max: The maximum value.

  • p2p: The peak-to-peak value = (max - min)

  • ∫: The integrated value, only for current and power.

• accumulators: The integrated charge and energy values.

• source: Either sensor (on instrument) or stream_buffer (on host).

Here is an example statistics data structure:

{
  "time": {
    "range": {"value": [29.975386, 29.999424], "units": "s"},
    "delta": {"value": 0.024038, "units": "s"},
    "samples": {"value": 48076, "units": "samples"}
  },
  "signals": {
    "current": {
      "µ": {"value": 0.000299379503657111, "units": "A"},
      "σ2": {"value": 2.2021878912979553e-12, "units": "A"},
      "min": {"value": 0.00029360855114646256, "units": "A"},
      "max": {"value": 0.0003051375679206103, "units": "A"},
      "p2p": {"value": 1.1529016774147749e-05, "units": "A"},
      "∫": {"value": 0.008981212667119223, "units": "C"}
    },
    "voltage": {
      "µ": {"value": 2.99890387873055,"units": "V"},
      "σ2": {"value": 1.0830626821348923e-06, "units": "V"},
      "min": {"value": 2.993824005126953, "units": "V"},
      "max": {"value": 3.002903699874878, "units": "V"},
      "p2p": {"value": 0.009079694747924805, "units": "V"}
    },
    "power": {
      "µ": {"value": 0.000897810357252683, "units": "W"},
      "σ2": {"value": 1.9910494110256852e-11, "units": "W"},
      "min": {"value": 0.0008803452947176993, "units": "W"},
      "max": {"value": 0.0009152597631327808, "units": "W"},
      "p2p": {"value": 3.49144684150815e-05, "units": "W"},
      "∫": {"value": 0.026933793578814716, "units": "J"}
    },
    "current_range": {
      "µ": {"value": 4.0, "units": ""},
      "σ2": {"value": 0.0, "units": ""},
      "min": {"value": 4.0, "units": ""},
      "max": {"value": 4.0, "units": ""},
      "p2p": {"value": 0.0, "units": ""}
    },
    "current_lsb": {
      "µ": {"value": 0.5333222397870035, "units": ""},
      "σ2": {"value": 0.24889270730539995, "units": ""},
      "min": {"value": 0.0, "units": ""},
      "max": {"value": 1.0, "units": ""},
      "p2p": {"value": 1.0, "units": ""}
    },
    "voltage_lsb": {
      "µ": {"value": 0.5333430401863711, "units": ""},
      "σ2": {"value": 0.24889309698100895, "units": ""},
      "min": {"value": 0.0, "units": ""},
      "max": {"value": 1.0, "units": ""},
      "p2p": {"value": 1.0, "units": ""}
    }
  },
  "accumulators": {
    "charge": {"value": 0.0, "units": "C"},
    "energy": {"value": 0.0, "units": "J"}
  },
  "source": "sensor"
}