be stored as programming instructions in memory 44 for use by microprocessor 40 fig5 is a simplified flowchart 100 showing steps in accordance with the present invention flowchart 100 begins at start block 102 at block 104 the field effect transistors 16 22 are controlled as described above a drive current is applied at block 106 by power source 12 and the resultant current i s is measured at block 108 for example using analog to digital converter 58 at block 110 the measured current i s is compared with a threshold level the threshold can be set as desired for example it may be desirable to have the threshold sufficiently high to avoid falsely identifying a current leakage path if the current i s is less than the threshold operation continues without any fault identifying however if the sensed current is greater than the threshold an output warning can be provided at block 112 additionally or alternatively at block 114 the flow measurements can be compensated based upon the amount of current leaking through the ground path and the compensated flow measurement can be output at block 116 in addition to comparing to a threshold as illustrated at block 110 other diagnostic techniques can be utilized including monitoring the leakage current for trends over a period of time sudden change in the leakage current or other techniques further the output 112 can include additional information including the value of the leakage current the resistance of the path to ground a residual life estimate before which service will be required a percent error in the flow measurements due to the leakage current etc although the present invention has been described with reference to preferred embodiments workers skilled in the art will recognize that changes may be.