Abstract: Method and apparatus are provided for sealing an open end of a sheathed cable. After removing a length of insulating jacket, the open end of the cable is placed in a pressure block and a viscous sealant material is injected into the block and into the open end of the cable. After injection, the cable is removed from the block and the sealant allowed to cure to a gel-like consistency. Fluid which may invade the interior of the cable above the seal is, therefore, prevented from passing by the seal and entering a transducer or other instrument secured to the end of the cable. In the preferred embodiment, a cable head, O-ring and transducer body are also provided to enclose the transducer in a substantially waterproof housing.

Abstract: Apparatus and method are provided to ensure accuracy of a measurement signal obtained using a potentiometric sensor placed in a solution. The apparatus includes an interface amplifier that generates a relatively large turn-on bias current whenever the amplifier is initially powered on. To avoid polarization of the potentiometric sensor by the turn-on bias current, a switch device is used to direct the turn-on bias current along a path away from the potentiometric sensor. The switch device is controlled using a timer circuit that causes a change in position of the switch device after a predetermined time delay. During the time delay, the bias current reduces to a normal value and polarization of the potentiometric sensor has been avoided. An accurate measurement of a physical parameter associated with the solution can then be taken without the detrimental effect of the turn-on bias current on the potentiometric sensor.

Abstract: An accurate analog measurement system is provided for reducing the effects, characterized by variations in gain and offset, that analog signals experience when transmitted from one point to another. The accurate analog measurement includes at least one transducer having a reference signal, scaling signal and output signal. The reference signal provides the baseline relative to which the scaling and output signals are measured. Indicative of the phenomena being measured by the transducer is the output signal. The scaling signal, preferably, represents the maximum possible output signal. The present invention also includes means for forcing the reference, scaling and output signals onto a common path so that each signal experiences the same variations when transmitted to a processing station of the present invention.

Abstract: An apparatus and method are provided for reducing the effects that common mode currents and/or voltages have on the measurements made by instrumentation that senses physical phenomena. The apparatus includes a cell having a first sensor, a second sensor and a passageway for containing the fluid to be measured. The cell, sensors and passageway are symmetrically disposed about an axis. Due to this symmetry, a ground can be located at the axis of symmetry. The apparatus also includes first and second measuring circuits associated, respectively, with the first and second sensors. The first measuring circuit produces a signal respresentative of the measured parameter between the ground and the first sensor. The second measuring circuit provides a like function for the second sensor. The signals produced by the first and second measuring circuits are summed by a potentiometer.