Patent ID: 7454959

Claim:
Method to supply a defined fluid flow, especially for liquid chromatography, a) in which a total flow (f 0 ) is split into an internal excess flow (f ie ) in an excess branch and an internal work flow (f iw ) working branch b) wherein the split ratio between the internal work flow (f iw ) and the internal excess flow (f ie ) is determined by the reverse ratio of a fluidic resistor ( 7 ) in the working branch and fluidic resistor ( 9 ) in the excess branch, and c) where the excess branch and the working branch are interconnected at the outputs of the two fluidic resistors ( 7 , 9 ) via a cross-branch, d) in which the balance flow (f bal ) occurring between the outputs of the fluidic resistors ( 7 , 9 ) is measured with a flow sensor ( 108 ), e) where further down the working branch an external work flow (few can be supplied to an operating device downstream of the device ( 100 ), f) after which further down the excess branch an adjustable resistance device ( 11 ) is installed, g) where by control of the resistance value of the adjustable fluidic resistance device ( 110 ) the balance flow (f bal ) is regulated in such manner that the balance flow (f bal ) is in the temporal median, generally equal to zero or equal to a preset offset value, whose value is small in comparison to the internal work flow (f iw ), wherein the resistance value if the adjustable fluidic resistance device for the determination of the internal work flow (f iw ) and/or external work flow (f ew ) further down the working path is temporarily set in such manner that a balance flow (f bal ) of unequal to zero results, and the internal work flow (f iw ) expected in normal operating mode and/or the external work flow (f ew ) is determined from the signal (S vai ) of the flow sensor ( 108 ), wherein the adjustable fluidic resistance device ( 110 ) is shorted for measuring the internal work flow (f iw ) in the cross-branch and/or adjusted to a value equal to zero, whereby the cross-branch preferably exhibits a fluidic resistance of equal to or near zero.