Abstract: A test apparatus for measuring blood characteristics comprises a measuring head having a measuring electrode and a reference electrode arranged in spaced relationship and a closure membrane covering a portion of said head, and an attachment connectable to said head having a wall defining a support membrane which is engageable on the closure membrane. The attachment defines a chamber for the blood sample in which the support membrane forms a bottom wall thereof so that the membrane supporting the blood is in contact with the closure member and thus is capable of being heated by a heater contained in the head without coming into contact with or contaminating the blood sample. The attachment while permitting the measurement to be made does not allow the blood being tested to come into contact with the measuring head. The attachment may be either disposed of or cleaned for re-use.

Abstract: A gas mixing device comprises a plurality of gas lines for the conveyance of the separate gases to be mixed, each of which has a pressure regulator with a pressure control. A common gas mixture line is connected to each of the gas lines downstream of the pressure controls therein and a constant admission pressure regulator is provided in the mixture line. Control pressure is provided from a control pressure source which, for example, may be at the tapping of the gas mixture line. The control pressure is connected to each of the pressure controls for the pressure regulators and the gas lines and this control pressure is regulated by control means which may be in response to the pressure in each of the individual gas lines or in response to the pressure in the common gas mixture line downstream of the constant admission pressure regulator means.