1 an axial along the flow distance may separate the returns heat source 9 2 and the returns temperature probe 9 1 to provide heat conduction dissipation information a returns gas detector 11 is adapted to detect the presence of gas in the drilling fluid returns a returns resistivity sensor 12 is adapted to measure the resistivity of the drilling fluid returns in mud tanks 40 the drilling fluid is processed or cleaned up after removal of at least a portion of the drill cuttings after the shaker 4 a series of compartments or tanks may be used to monitor filter and otherwise condition the drilling fluid for recycle the drilling fluid downhole typically the last compartment or tank just prior to the suction of the mud pumps is used to finally condition the drilling fluid for example by addition of additives such as weighting material or other additives a sonic level sensor 13 measures the drilling fluid level in one or more compartments or tanks of the mud tanks 40 a supply resistivity sensor 14 measures the resistivity and a supply gas detector 15 measures the gas content of the drilling fluid a plurality of sensors which may include some or all of a supply doppler velocity meter 16 a supply gamma ray gr source 17 a supply discreet bulk.