Step level probe

Claim 2

An elongated probe for measuring the depth of conductive free flowing materials in a tank comprising: a series of hollow contact units each having an electrode portion adapted to be contacted by conductive free flowing material in the tank, each contact unit having a lead wire attachment means disposed within the probe and electrically connected to the electrode portion; a series of hollow insulator units, the series of hollow contact units and hollow insulator units being arranged alternatively; the series of contact units and insulator units having mutual attachment means so that the probe may be assembled unit by unit as an elongated assembly; a base plug in one of the units which is an end of the series of contact and insulator units; and sealing means between the insulator units and contact units and sealing means cooperating with the base plug so as to prevent the free flowing material from reaching the interior of the probe.

Claim 3

A probe as claimed in claim 1 in which the contact unit electrode portion comprises a conductive body having a contact surface, means insulatedly supprting said body so that each conductive surface is displaced from the general surface of the probe and means connecting said contact surface to the lead wire attachment means.

Claim 4

A probe as claimed in claim 1 in which each contact unit electrode portion comprises a conductive arm insulated from contact with the conductive free flowing material, the conductive arm extending outwardly from the main axis of the elongated probe and a conductive body having contact surface, the body being attached to the arm so that substantial electrical contacts with the conductive liquid can occur only at a series of discrete and isolated areas, which lack a continuous joining surface therebetween.

Claim 5

A probe as claimed in claim 3 in which the body having a contact surface is a disc, said disc having one major surface facing away from the probe axis, the other major surface and disc periphery being insulated from contact with the conductive free flowing material.

Claim 6

A probe as claimed in claim 1 in which the contact unit comprises a pipe union type fitting of conductive material having an outer perpheral surface extending between the two adjacent insulator units.

Claim 7

A probe as claimed in claim 1 in which the base plug is formed of a conducting material and is grounded.

Claim 8

A probe as claimed in claim 1 in which the contact unit comprises a fitting of conducting material having a transverse surface within the next adjacent insulator at the distal end from the base plug, and a hole drilled and tapped in said fitting at said surface, the lead wire attachment means comprising a screw adapted to fit in said drilled and tapped hole so as to secure the wire to said surface in electrical contact therewith.

Claim 9

A probe as claimed in claim 1 in which resistor elements are accommodated within the probe and are connected between one contact unit and the next contact unit so as to Reduce the number of wires in the hollow of the probe at the top end substantially below the number of contact units.

Claim 10

A probe as claimed in claim 8 in which a resistor element is connected between each contact unit and its fellow so as to reduce the number of wires in the hollow of the probe at the top to not more than two.

Claim 11

A probe as claimed in claim 1 and further comprising an indicating circuit having a supply and an indicating means and an operating circuit having a supply wherein contact units at predetermined fractions along the length of the probe are connected to the relay coils in the operating circuit, the relays being external to the probe and the relay contacts being connected in the indicating circuit and adapted to switch parallel resistors successively across the indicating circuit supply as the liquid rises so that the depth is indicated by the indicating means.

Claim 12

A probe as claimed in claim 8 and further comprising an indicating circuit having a supply and an ammeter and a relay operating circuit having a supply wherein contact units at predetermined fractions along the length of the probe are connected to relays in the operating circuit, the indicating circuit comprising a number of resistors external to the probe, said external resistors being connected to contact units adjacent those at said predetermined fractions along the length, said resistor elements accommodated within the probe and said external resistors being in series parallel arrangement with the relay contacts across the indicating circuit so that as the liquid level rises said resistor elements accommodated within said probe are successively short circuited by the liquid so that the value of current gives an approximate indication of liquid level between the predetermined fractions along the length of the probe, the relays operating so that when the liquid level rises to said predetermined fraction along the length the external resistances are successively paralleled across the indicating circuit, so that the value of current giving an accurate indication of liquid level at said predetermined fractions along said length.

Claim 13

A probe as claimed in claim 1 and further comprising: an indicating circuit, said indicating circuit having a supply means, indicating means and a series of switching means; an operating circuit having a supply means and a series of relay coils for operating said series of switching means, each relay coil being connected to a probe contact unit so as to operate said series of switching means successively as the liquid level rises; said indicating circuit further comprising at least one auxiliary circuit for performing an auxiliary function of alarm or an operation; said auxiliary circuit comprising a relay, the coil of said auxiliary circuit relay being connected in series with a further switching means which is operated by one of the relay coils of the series in the operating circuit; the auxiliary circuit relay coil being connected in series with a pair of its own contacts and yet another switching means operated by a corresponding relay coil so that the auxiliary circuit relay will continue to allow indication or operation after said one of said relay coils has ceased to be energized until said yet another switching means operates consequent upon a change in energization in the coil corresponding thereto in the operating circuit.

Claim 14

A probe and circuit as claimed in claim 12 in which the auxiliary circuit relay contacts operate an alarm circuit and the auxiliary circuit relay coil is operated by a switching means corresponding to a relay connected to a probe contact unit near one end of the probe and the coil corresponding to the further one of said switching means is connected to a relay adjacent to the probe contact unit near one end of the probe but closer to the centre so that the alarm signal is not affected by changes in level which are insubstantial relative to the distance between two adjacent probe contact units.

Claim 15

A probe and circuit as claimed in claim 12 in which the auxiliary circuit relay contacts operate a circuit which alters the level of the liquid and the auxiliary circuit relay coil is operated by a switching means corresponding to a relay connected to a probe contact unit near one desirable liquid level limit and the coil corresponding to the further one of said switching means connected to a probe contact unit near another desirable liquid level limit, so that when the level reaches said one probe contact unit near the one desirable liquid level the relay circuit operates to alter the liquid level so as to tend to bring it near the other desirable liquid level.