Two wire temperature and fluid level limit switch

Patent metadata

Field	Value
Publication number	US-9389115-B2
Application number	US-201414181177-A
Country	US
Kind code	B2
Filing date	Feb 14, 2014
Priority date	Feb 15, 2013
Publication date	Jul 12, 2016
Grant date	Jul 12, 2016

Abstract

A two-wire system for monitoring fluid level and temperature including a pair of electrical interconnect wires bridged by a fluid level switch and a thermal sensing element. One of the fluid level switch or the thermal sensing element bypasses the other during a trigger event.

First claim

What is claimed is:

1. A two-wire system for monitoring fluid level and temperature comprising:
a pair of electrical interconnect wires;
a fluid level switch bridging said electrical interconnect wires;
a thermal sensing element bridging said electrical interconnect wires;
wherein:
one of said fluid level switch and said thermal sensing element bypasses the other during a trigger event:
said thermal sensing element comprises a thermal limit switch, said thermal limit switch biased open and triggered to close at a trigger temperature; and
said fluid level switch biased closed and triggered to open at a fluid trigger level.

2. The two-wire system as described in claim 1 , further comprising:
a thermal limit bias resistor; and
a sensor bias resistor.

3. The two-wire system as described in claim 2 , wherein said sensor bias resistor has a resistance greater than the switch contact resistance of said fluid level switch.

4. The two-wire system as described in claim 2 , wherein said thermal limit bias resistor has a resistance greater than the switch contact resistance of said fluid level switch.

5. The two-wire system as described in claim 1 , wherein said thermal sensing element comprises:
a thermal variable sensing element; and
a thermal non-variable resistive element.

6. The two-wire system as described in claim 5 , wherein said fluid level switch is biased open and triggered to close at a fluid trigger level.

7. A two-wire system for monitoring fluid level and temperature comprising:
a single pair of electrical interconnect wires;
a fluid level switch providing a first electrical pathway between said single pair of electrical interconnect wires; and
a thermal sensing element providing a second electrical pathway between said single pair of electrical interconnect wires;
wherein:
said fluid level switch and said thermal sensing element operate in concert to provide a single signal in said single pair of electrical interconnect wires;
said thermal sensing element comprises a thermal limit switch, said thermal limit switch biased open and triggered to close at a trigger temperature; and
said fluid level switch biased closed and triggered to open at a fluid trigger level.

8. A method of monitoring fluid level and temperature comprising:
monitoring a pair of electrical interconnect wires;
sensing a fluid level using a fluid level switch bridging said electrical interconnect wires;
sensing a fluid temperature using a thermal sensing element bridging said electrical interconnect wires;
triggering said fluid level switch to open at a fluid trigger level; and
triggering said thermal sensing element to close at a trigger temperature, said thermal sensing element comprising a thermal limit switch;
wherein one of said fluid level switch and said thermal sensing element bypasses the other during a trigger event.

9. A two-wire system for monitoring fluid level and temperature comprising:
a pair of electrical interconnect wires;
a fluid level switch bridging said electrical interconnect wires;
a thermal sensing element bridging said electrical interconnect wires;
one of an analog gauge and an electronic control unit in communication with said single pair of electrical interconnect wires;
a monitoring device configured to determine a fluid temperature when said fluid level switch is biased open and to signal a fluid level when said fluid level switch is triggered to close;
wherein:
one of said fluid level switch and said thermal sensing element bypasses the other during a trigger event;
said thermal sensing element comprises a thermal variable sensing element;
said fluid level switch is biased open and triggered to close at a low fluid trigger level.

10. The two-wire system as described in claim 9 , further comprising:
a magnetic float;
wherein said fluid level switch is triggered by said magnetic float.

11. The two-wire system as described in claim 10 , wherein said fluid level switch disconnects said thermal sensing element when said fluid level switch is closed.

12. A two-wire system for monitoring fluid level and temperature comprising:
a pair of electrical interconnect wires;
a fluid level switch bridging said electrical interconnect wires;
a thermal sensing element bridging said electrical interconnect wires;
an electronic control unit in communication with said pair of electrical interconnect wires;
a first resistor bridging said electrical interconnect wires and having a first end and a second end, said first resistor arranged in parallel with said fluid level switch;
a second resistor arranged in series with said first resistor and connected to said first end and said electronic control unit; and
a third resistor arranged in series with said first resistor and connected to said second end and said electronic control unit;
wherein:
said electronic control unit utilizes said pair of electrical interconnect wires to diagnose an electrical short location; and
one of said fluid level switch and said thermal sensing element bypasses the other during a trigger event.

13. The two-wire system as described in claim 12 , wherein said electronic control unit diagnoses an open circuit fault by the ratio of the first, second, and third resistors.

14. A two-wire system for monitoring fluid level and temperature comprising:
a single pair of electrical interconnect wires;
a fluid level switch providing a first electrical pathway between said single pair of electrical interconnect wires; and
a thermal sensing element providing a second electrical pathway between said single pair of electrical interconnect wires;
a monitoring device in communication with said single pair of electrical interconnect wires;
wherein:
said fluid level switch and said thermal sensing element operate in concert to provide a single signal in said single pair of electrical interconnect wires;
said thermal sensing element comprises a thermal variable sensing element;
said fluid level switch is biased open and triggered to close at a fluid trigger level; and
said monitoring device is configured to determine a fluid temperature when said fluid level switch is biased open and to signal a fluid level when said fluid level switch is triggered to close.

15. The two-wire system as described in claim 14 , further comprising:
a first resistor bridging said single pair of electrical interconnect wires and having a first end and a second end;
a second resistor arranged in series with said first resistor and connected to said first end; and
a third resistor arranged in series with said first resistor and connected to said second end; and
wherein said monitoring device said first, second and third to diagnose a circuit fault.

16. A method of monitoring fluid level and temperature comprising:
monitoring a pair of electrical interconnect wires;
sensing a fluid level using a fluid level switch bridging said electrical interconnect wires;
sensing a fluid temperature using a thermal sensing element bridging said electrical interconnect wires;
monitoring said thermal sensing element utilizing a monitoring device to determine a fluid temperature;
displaying said fluid temperature when said fluid level switch is in an open position; and
displaying a fluid level when said fluid level switch is in a closed position, said fluid level switch biased open and triggered to close at a fluid trigger level;
wherein one of said fluid level switch or said thermal sensing element bypasses the other during a trigger event.

17. A two-wire system for monitori

Assignees

• Eaton Corp

Inventors

• Fritz Todd
• Manyala John
• Pauls Ryan
• Metheny Eric

Classifications

• G01D21/02

  Measuring two or more variables by means not covered by a single other subclass · CPC title

• G01F23/62

  using magnetically actuated indicating means · CPC title

• G01F23/38 Primary

  using magnetically actuated indicating means · CPC title

• G01K7/24

  in a specially-adapted circuit, e.g. bridge circuit · CPC title

• G01F23/74

  for sensing changes in level only at discrete points · CPC title