Pressurized cable-sheath leak locating instrument

A pressurized cable-sheath leak locating instrument comprising:

• (a) an air pressurized cable-sheath surrounding a plurality of communication conductors where said cable-sheath is pressurized by means of a compressor-dehydrater that supplies the air to said cable-sheath by way of an airpipe manifold connected to an air hose that in turn is connected to a cable splice case enclosing said cable sheath where said airpipe manifold has attached a manifold pressure valve and a cable pressure valve,
• (b) a pneumatic pressure hose assembly having a pneumatic hose with a first pneumatic pressure connector on one end and a second pneumatic pressure connector on the other end where the first pneumatic pressure connector is connected to the manifold pressure valve on said airpipe manifold,
• (c) a pneumatic air flow hose assembly having a pneumatic hose with a first pneumatic flow connector on one end and a second pneumatic flow connector on the other end where the first pneumatic flow connector is connected to the cable pressure valve on said airpipe manifold,
• (d) a pneumatic/electronics unit,
• (e) a pneumatic pressure receptacle having, with respect to said pneumatic/electronics unit, an external end and an internal end, where the external end is connected to the second pneumatic pressure connector on said pneumatic pressure hose assembly,
• (f) a pneumatic flow receptacle having, with respect to said pneumatic/electronics unit, an external end and an internal end, where the external end is connected to the second pneumatic flow connector on said penumatic air flow hose assembly,
• (g) a pressure transducer having a pneumatic input and an electrical output where said transducer is used for converting the air pressure in the interior of said cable-sheath to a d-c voltage that is proportional to the air pressure,
• (h) a flow transducer having a pneumatic input, a pneumatic output, and an electrical output, where the pneumatic output is connected to the internal end of said pneumatic flow receptacle and where said transducer is used for converting the air flow rate being communicated through the interior of said cable-sheath to a d-c voltage that is proportional to the air flow rate,
• (i) a three port pneumatic connector where first port is connected to the internal end of said pneumatic pressure receptacle, where second port is connected to the pneumatic input of said pressure transducer and where the third port is connected to the pneumatic input of said flow transducer,
• (j) an analog-to-digital converter having an input and an output, where said converter is used to convert the air pressure and the air flow rate d-c voltages to equivalent digital signals,
• (k) an electrical read-pressure switch that when depressed the electrical output of said pressure transducer is applied to the input of said analog-to-digital converter,
• (l) an electrical read-flow switch that when depressed the electrical output of said flow transducer is applied to the input of said analog-to-digital converter,
• (m) an electronic calculator having a plurality of logic/digital circuits, computer program storage and retrieval circuits, and a computer program that solves the following set of equations that when solved provide distance and air flow data respectively that is used to limit the area of search of an air leak in said pressurized cable sheath, and where the digitized pressured and flow rate data used in the calculations are supplied from the output of said analog-to-digital converter:
• ##STR3## where D=maximum distance in feet (meter) of air leak from the pressure source measuring point,
• P=pressure in psi (kPa) in cable at a given location,
• F=gas-flow rate in SCFH (m.sup.3 /hr) in cable sheath,
• R=pneumatic resistance per 1000 feet (300 meter) of a particular size and gauge of cable, ##STR4## where F=gas-flow rate in SCFH (m.sup.3 /hr) in cable sheath,
• P.sub.1 and P.sub.2 =pressure readings in psi (kPa) of two pressure points in the cable sheath separated by a known distance d,
• d=distance in feet (meter) between cable sheath pressure testing valves,
• R=pneumatic resistance per 1000 feet (300 meter) of a particular size and gauge of cable,
• (n) a display connected to said electronics calculator, that displays for the user the interim data being set into the calculator and the final distance and air flow data as solved by the set of equations, and
• (o) a keyboard and BCD logic circuit connected to said electronics calculator that allows the user to selectively enter into said keyboard the entry commands relative to the interim pressure and gas flow data, as displayed on said display, as well as other data required to solve said set of equations.