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FIG. 1. Diagram of a dual-probe heat-pulse (DPHP) sensor with heater probe and temperature probe. The plane passing through the heater and temperature probes corresponds to the x–y plane in Fig. 2 and defines the area in which the spatial sensitivity of the DPHP method is characterized. The plane is oriented normal to the probes and passes through the temperature probe as the location where temperature is measured with a thermistor or thermocouple. See Heitman et al. (2003) for a more detailed schematic diagram that includes cutaway views of the probes and sensor body.
