with Hall Probe Ge p-type HPP-33 The set-up, DHE-33 consists of two sub units to handle the probe parameters (probe current and hall voltage) and measurement of temperature. While the probe current is generated and measured by a constant current source (0-20mA) having a resolution of 10mA, the hall voltage is measured by a high input resistance millivoltmeter in the range 0-200mV having a resolution of 100microvolt. The Probe.