Low-water cut-off system
View Patent ↗A low-water cut-off system [A] determines if fluid [W] within a boiler [ 16 ] or other enclosure drops below a predetermined level within the enclosure. A signal generator introduces a signal into the enclosure so that the signal is present for sensing at the predetermined level, where a probe [ 14 ] is provided for sensing the signal if present as occurs if the water is at the predetermined level. A control [ 18 ], which includes a microcontroller [ 25 ], is responsive to the probe for providing a control function in response to whether the signal is so sensed by the probe, and so to determine if water has dropped below the predetermined level. The function may be causing alarm signalling or boiler heating cut-off. Self-test and time delay features are also included. Provision is made so that the control compensates for variation in electrical conductivity of the water through which the probe signal is sent.
1. A low-water cut-off system for determining if water drops below a predetermined level within a water-containing enclosure, comprising:
a signal generator operative to introduce a signal into the water-containing enclosure such that the signal is present for sensing within water at the predetermined level,
a probe at the predetermined level capable of sensing the presence of the signal within the water if the water is at the predetermined level, and
a control responsive to the probe sensing for providing a control function in response to whether the signal is so sensed by the probe, in order to indicate thereby whether water has dropped below the predetermined level wherein the signal is transmitted through water in the enclosure according to the value of electrical conductivity of the water, the system including a provision for selectively adjusting the sensitivity of the probe sensing according to said value.
2. The low-water cut-off system according to claim 1 wherein the control function is an indication that water has dropped below the predetermined level, and including a circuit arrangement to selective set either a delay on make or delay on break time, or both, for indication that water has dropped below the predetermined level.
3. The low-water cut-off system according to claim 1 wherein the signal is of periodic nature.
4. A fluid-level detecting system for determining if fluid is at a predetermined level within a fluid-containing space in which fluid could be at the predetermined level, the fluid being transmissive of a signal, comprising:
signal generating circuitry capable of introducing such a signal into the fluid-containing space such that the introduced signal is present for sensing within fluid at the predetermined level if, and only if, the fluid is at least as high as the predetermined level,
a probe and probe-responsive circuitry capable of sensing the presence of the introduced signal within the fluid at the predetermined level, and
control circuitry capable of providing a control function in response to whether the introduced signal is so sensed, in order to indicate whether the fluid has a level is at least as high as the predetermined level wherein the signal is transmitted through fluid in the fluid-containing space according to the value of electrical conductivity of the fluid, the system including a provision for selectively adjusting the sensitivity of the probe sensing according to said value.
5. Apparatus responsive to presence of a fluid at a predetermined level within a fluid-receiving space in which the fluid can rise to the predetermined level and for providing a control function if a level of the fluid shifts from the predetermined level, comprising:
a signal generating circuitry capable of introducing a level-determining signal into the fluid-containing space such that the periodic signal is present for sensing within fluid at the predetermined level if, and only if, the fluid level is at least as high as the predetermined level,
a probe and probe-responsive circuitry capable of sensing the presence of the periodic signal within the fluid at the predetermined level, and
control circuitry capable of providing a control function in response to whether the level-determining signal is so sensed, in order to indicate whether the fluid has a level is at least as high as the predetermined level,
whereby the control function may be used for alarm or cut-off purposes if the fluid level shifts relative to the predetermined level ,wherein the signal is transmitted through fluid in the fluid-receiving space according to the value of electrical conductivity of the fluid, the system including a provision for selectively adjusting the sensitivity of the probe sensing according to said value.
6. The apparatus as set forth in claim 5 , wherein the probe is configured for being inserted into the fluid-receiving space at the predetermined level.
7. The apparatus as set forth in claim 6 , wherein the probe-responsive circuitry comprises a detector circuitry interconnected with the probe for receiving and determining receiving by the probe of the periodic signal.
8. The apparatus as set forth in claim 7 , wherein the fluid has a transmissivity characteristic transmissivity value representing the degree of transmissivity of the periodic signal through the fluid, the detector circuitry including provision for adjusting sensitivity of the detector circuit according to said value.
9. A method for determining the presence of a fluid at a predetermined level within a fluid-receiving space in which the fluid can rise to the predetermined level, comprising:
introducing a signal into the fluid-receiving space such that the signal is present for sensing within fluid at the predetermined level, wherein said signal is transmitted through water in the fluid-receiving space according to a value of electric conductivity of the water,
providing a probe at the predetermined level for sensing said signal,
sensing for the presence of the signal within the fluid at the predetermined level,
providing a control function in response to whether the signal is so sensed, in order to indicate whether the fluid is present at the predetermined level, and
selectively adjusting the sensitivity of the probe sensing according to said value.
10. The method of electronically determining whether fluid is at a predetermined level within a fluid-receiving space, comprising:
introducing a signal into the fluid-receiving space such that the signal is present for sensing within fluid at the predetermined level, wherein said signal is transmitted through water in the fluid-receiving space according to a value of electric conductivity of the water,
providing a probe at the predetermined level for sensing said signal,
sensing for the presence of the signal within the fluid at the predetermined level, and
providing a control function in response to whether the signal is so sensed, in order to indicate whether the fluid is or is not present at the predetermined level, and
selectively adjusting the sensitivity of the probe sensing according to said value.
11. The method accord to claim 10 wherein the step of sensing for the presence of the signal is carried out by using a signal-responsive probe inserted into the fluid-receiving space at the predetermined level.
12. The method accord to claim 11 wherein the signal introduced into the fluid-receiving space is of a periodic nature.
13. The method accord to claim 12 wherein the periodic signal is coupled to the fluid in the space from a periodic signal generating circuit.
14. The method accord to claim 13 wherein the step of sensing for the presence of the signal at the predetermined level is carried out by using a detector circuit interconnected with the probe.
15. The method accord to claim 14 wherein the fluid has a characteristic having a value, subject to possible variation, which determines transmissivity of the signal through the fluid, the method further comprising adjusting sensitivity of the detector circuit according to said value.
16. The method accord to claim 15 wherein the control function is an indication that fluid is lower than said predetermined level.
17. The method accord to claim 10 wherein at least the sensing and control function providing steps are carried out under microcontroller control.
18. The method accord to claim 10 wherein the control function is an indication that fluid is lower than the predetermined level, and at least the sensing and control function providing steps are carried out by microcontroller control, and by further using microprocessor control to determine either a delay on make or delay on break time, or both, for indication that fluid is lower than said predetermined level.