Patent GB-1105048-A (GB)
Title: Apparatus for detecting ionizing fluid
IPC: G01N27/12
Filed: 1966-10-17
Abstract: 1,105,048. Measuring electrically. IPSEN INDUSTRIES Inc. Oct. 17, 1966 [Oct. 23, 1965], No. 46346/66. Heading G1N. An element having a resistance which depends upon the amount of an ionizing fluid, such as water, present, consists of a porous mass composed of electrically conductive particles (SS, Fig. 5, not shown), dielectric particles (G) and particles (S) of a salt. The element is in the form of a short rod 14, Fig. 3, having electrodes 29, 31, and is contained in a casing 19 having apertures 19a for access of the water, the casing being carried at the end of a tube 18 through which a conductor 47 extends together with a conductive screen 46 for the conductor, and insulating layers 45, 48. The conductor 47 is connected to the electrode 31 by means of a male 38 and female 44 connector at one end, and to measuring apparatus contained in a housing (17, Fig. 2, not shown) at the other. The element may be submerged in a bath (13, Fig. 1, not shown) of quenching oil associated with a heat treating furnace (11), in order to sense an undesirable excess of water in the oil. In the measuring circuit Fig. 6 (not shown), an element (14) is transformer fed from a 5Kcs oscillator (81), and the resulting current flow is detected by a positive polarity rectifying diode (89), and a negative polarity rectifying diode (92). A triode (110) has a relay coil (111a) in its anode circuit, and has its cathode maintained at a fixed voltage of Eb = 4 volts from a potentiometer (99). The negative polarity rectifier (92) is connected to the triode grid (110c) via a 24 volts Zener diode (104) so that the relay coil is de-energized by cut-off of the triode only when the rectified voltage drops below this level indicating a resistance fall of the sensing element corresponding to a permissible maximum concentration of water in the quenching oil (12, Fig. 1, not shown). Additionally, the relay is required to de-energize if the sensing element develops a fault such as disconnection of the electrodes (29, or 31) or disintegration of the porous mass, which fault would appear as a substantial fall in the capacity (14c) of the element. Such a reduction in capacity causes the positive rectifier (89) output, (at 98), to fall below the cathode bias level of Eb = 4 volts, to which it is normally clamped by a diode (96) when it exceeds 4 volts. The voltage (at 89) is transmitted via a resistor (105) to the grid and the relay is deenergized. The relay contacts (111c operate a lamp (22G) during normal furnace operating conditions; and in the event of a fault or of an excess of moisture, contacts (111b) operate an alarm lamp (22R) and a bell (21), and contact 111d turns off the furnace operating control. The conductive particles SS in the sensing element may be of stainless steel, chromium or molybdenum, the dielectric particles G may be of glass or plastics material, and the salts may be potassium nitrate. In a typical fabrication procedure, particles of stainless steel, glass and potassium nitrate, are mixed and formed into a paste with water, the paste then being extruded in rod form under high-pressure to squeeze out the water. Lengths of rod are then cut and heated to 800 to 900 degrees F. to fuse the glass and steel particles together.