GB1482494A - Pressure transducers - Google Patents

Abstract

1482494 Measuring pressure electrically TYCO LABORATORIES Inc 8 Aug 1975 33267/75 Heading G1N [Also in Division H1] A pressure transducer of the type utilizing variation in resistance in response to strain comprises a strain-sensing element 36 preferably in a wheatstone bridge arrangement of electrical resistances 49, 51, 53, 55, Fig. 5, the element being bonded to a diaphragm 23 of e.g. stainless steel, quartz, sapphire which is clamped between an internal shoulder (24), Fig. 2 (not shown) and a flange 20, Fig. 1, of a fitting 12 by bending the wall of one end of a hollow case 22, and a terminal board 26 having conductive tracks (54 a-d), Fig. 4 (not shown) electrically connected to the wheatstone bridge, the board being clamped at the other end of the case between the internal shoulder (24) and a wall portion 32. The resistors 49-55 which are preferably encapsulated, and conductive tracks 46 a-d are formed of e.g. copper-nickel, nickelchromium alloy on a flexible carrier 38 made of polyimides or nitrocellulose paper by known printed circuit techniques, and as shown in Fig. 1, the tabs 42 are clamped between the terminal board and the shoulder (24) so that they are in pressurized contact with aligned tracks (54 a-d). The central position 40 of the carrier 38 and the tabs 42 are bonded respectively to the diaphragm and the shoulder (24) using an epoxy-phenolic adhesive which is heat cured under pressure either before the terminal board is clamped in position or after the transducer is completely assembled, a rubber block 58 being provided to uniformly distribute the pressure during the curing step. Vents 62 or (66), Fig. 2 (not shown), are provided to maintain one side of the diaphragm at ambient pressure, whereas the other side of the diaphragm is exposed via a passageway 16 to a fluid whose pressure is to be measured.