Abstract: A fluid arrangement for analyzing a fluid sample using an electrochemical measuring apparatus having an analyzing device with an inlet port and an outlet port, the outlet port connecting to an outlet tube, the inlet port connecting to an inlet tube having a sample fluid receiving end, and the inlet tube connecting at a junction along its length to one end of a fluid supply tube, which fluid supply tube is connected at its opposite end to at least one fluid source containing a fluid. In a first mode, the fluid from the supply source flows through the fluid supply tube to the junction and the fluid then flows simultaneously in a proximal direction and a distal direction within the inlet tube from the junction, and in a second mode, a fluid sample is drawn through the inlet tube past the junction and into the analyzing module.

Abstract: A testing module is provided having units which can be arranged seriatim to provide narrow through passageways linked to each other for quantitative determination of analytes passing through the units as by electrical testing with electrodes. Auxiliary passageways are preferably used in one unit to allow flushing of a first sample chamber without contamination from a second sample chamber. An electrode holder carries a membrane backed by a gel to aid in electrically linking the membrane to an electrode and to support the membrane in a substantially planar condition in use.

Abstract: Apparatus and a process for reducing peristaltic pump noise in a high impedance electrochemical measuring system by eliminating the noise at the pump source so as to minimize the effect of the noise on the precision and the response time of the measuring electrode. In a system having a high impedance measuring electrode connected to the elastomeric peristaltic tubing via a fluid conduit, a high impedance segment is disposed in the fluid conduit between the electrode and peristaltic tubing and means are disposed between the segment and peristaltic tubing for discharging the electrical noise generated by the action of the pump rollers over the peristaltic tubing. Preferably the discharging means is a conductive path electrically connected to an AC capacitive ground wherein the impedance of the capacitive ground is less than that of the segment. The segment may be a nonconductive liquid or gas such as air.