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This 900A video series of 6 videos is designed to help familiarize you with the basic operation of the 900A Micropressure System. The 900A was designed for measuring pressures in kidney tubules, and it has many applications. It has recently been used for measuring...more

The 900A is designed to measure hydrostatic pressure in small vessels and cells. Pressure ranges of -200 to +400 millimeters of mercury can be measured with stability and accuracy. The system's sensing element is an electrolyte-filled glass microelectrode with a tip diameter range of 2 to 5 microns. Pressures of electrolyte solutions are measured by maintaining a salt concentration gradient at the tip of the sensing electrode in dynamic equilibrium by applying an equal air pressure inside the microelectrode. The pressure reading appears on the front panel display and via the BNC recorder output. Because the piezo electric pressure controller uses external pressure and vacuum sources, pressures lower than -200 to greater than +400 mm Hg can be quickly and accurately measured at the microelectrode tip.

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WPI’s microelectrode holder-half-cells couple fluid-filled glass micropipettes to high input impedance amplifiers. A Ag/AgCl pellet (or a silver wire) molded into the holder body provides stable potential. Electrical connection is made via male 2mm pins or female 2mm sockets. The pipette may be mounted axially or at right angles to the holder. Pipettes are held with screw-caps or rubber gaskets (without caps). Filling WPI microelectrode holders with electrolytes containing chloride results in stable electrode potential. Suitable electrolytes include KCl, NaCl andCaCl₂. Holders are supplied for standard WPI single capillary tubing of 1.0, 1.2, 1.5 and 2.0mm outside diameters. (Call WPI regarding custom designs for other glass diameters.) The holder style you select will depend on your experimental application, space, and instrumentation.

Hints for selecting and ordering micropipette holders

1. Determine the required electrical connection on the holder. For...more