Abstract: An apparatus for determining total hardness in a fluid stream utilizing a first and second sodium ion selective electrode (ISE). The ion selective electrodes are in electrical communication with one another, having first and second reference electrodes, respectively, with a salt bridge therebetween, where the first ISE receives hard water and the second ISE receives soft water. A least one drain receives outflow from effluent fluid from the first and second sodium ISE sensors.

Abstract: A printhead for an inkjet printer employs an ink fill slot having an extended portion disposed as a depression on the primary surface of the printhead substrate. The barrier layer of the printhead forms the walls of the ink ejection chambers, the walls of and constrictions in the ink fill channels, and the contoured barrier lobes between the ink fill channels. The extended portion of the ink fill slot follows the contour of the barrier lobes such that the length of the substrate shelf between the ink fill channel constriction and the extended portion of the ink fill slot is equalized between ink ejection chambers.

Abstract: An ink fill slot can be precisely manufactured in a substrate utilizing photolithographic techniques with chemical etching, plasma etching, or a combination thereof. These methods may be used in conjunction with laser ablation, mechanical abrasion, or electromechanical machining to remove additional substrate material in desired areas. The ink fill slots are appropriately configured to provide the requisite volume of ink at increasingly higher frequency of operation of the printhead by means of an extended portion that results in a reduced shelf length and thus reduced fluid impedance imparted to the ink. The extended portion is precisely etched to controllably align it with other elements of the printhead.

Abstract: An ink fill slot can be precisely manufactured in a substrate utilizing photolithographic techniques with chemical etching, plasma etching, or a combination thereof. These methods may be used in conjunction with laser ablation, mechanical abrasion, or electromechanical machining to remove additional substrate material in desired areas. The ink fill slots are appropriately configured to provide the requisite volume of ink at increasingly higher frequency of operation of the printhead by means of an extended portion that results in a reduced shelf length and thus reduced fluid impedance imparted to the ink. The extended portion is precisely etched to controllably align it with other elements of the printhead.

Abstract: A process for manufacturing a thin film resistor substrate useful, for example, in fabricating an ink jet printhead, wherein discontinuous strips of conductive material are initially patterned on the surface of a resistive layer. These strips are formed using a first series of masking and etching steps of define an "X" dimension of a resistive heater element. Then, the conductive strips and resistive material therebetween are completely masked in preparation for a subsequent, second etching step used to remove the exposed portions of the resistive layer and thereby define a "Y" dimension of the resistive heater element. These steps leave smooth contours, good step coverage and high quality bevelled edges of the thus defined conductive and resistive layers. These layers are now ready for subsequent passivation layer, barrier layer and orifice plate deposition processes to complete a thin film printhead for use in an ink jet printer.