Most diesel engine fuel systems employ forward and return fuel flow lines. The return flow amount must be measured and subtracted from the forward flow amount to determine consumption. Inaccuracies in flow measurement in either direction can compound the amount of error in measurement. The amount of return flow varies by engine type - from as little as 10% of fuel consumption to a much as 1000% or more... necessitating very tight margins for error when measuring flows and calculating the difference. With regard to engines that use the return flow to cool unit injectors (e.g., CAT 3500/3600 Series, Detroit/MTU, and Cummins QS Series), the return flow temperature is substantially higher than the forward flow - leading to the possibility of error in measurement caused by the expansion of fuel.
FloScan has designed special temperature compensated systems to accurately measure and compensate for these inconsistencies. Each pair of FloScan sensors (forward and return) is individually calibrated and matched to the microprocessor-driven meterhead.