Product level monitoring in a chemical dispensing system

Abstract

A system and method for monitoring the levels of product in a chemical dispensing system. A probe assembly is operatively disposed in a container holding product to be dispensed. A detection circuit including an oscillator sensitive to the impendence coupled to the detector is selectively coupled to the probe assembly and produces a signal in response to the impedance of the probe assembly indicating if the level of product in the container has dropped below the probe assembly. The probe assembly includes conductive probes formed from corrosion resistant material infused with carbon and separated by an angle. The level of the first and second conductive probes is adjustable to provide control over the level of product to be detected. Multiple probe assemblies may be selectively coupled to the detection circuit in a repeating sequence by a multi-probe monitoring unit to allow monitoring of multiple containers by a single remote alarm.

What is claimed is: 
     
         1 . A monitoring unit for monitoring multiple probes in a chemical dispensing system, the monitoring unit comprising:
 a detection circuit including an input and an output, the detection circuit configured to output a first signal in response to detecting a low impedance at the input and output a second signal in response to detecting a high impedance at the input;   a switch matrix including a plurality of electrical input ports, and an electrical output port coupled to the input of the detection circuit; and   a processor operatively coupled to the switch matrix and configured to cause the switch matrix to selectively couple the electrical input ports to the electrical output port.   
     
     
         2 . The monitoring unit of  claim 1  wherein the processor is configured to initialize the monitoring unit by polling each electrical input port and flagging each electrical input port for monitoring that presents the low impedance. 
     
     
         3 . The monitoring unit of  claim 2  wherein the processor is configured to sequentially couple each flagged electrical input port to the electrical output port for monitoring by the detection circuit. 
     
     
         4 . The monitoring unit of  claim 1  wherein the detection circuit comprises an oscillator configured to output the first signal when the input is coupled to the low impedance and output the second signal when the input is coupled to the high impedance. 
     
     
         5 . The monitoring unit of  claim 4  wherein the first signal is a time-varying voltage at a first frequency and the second signal is a time-varying voltage at a second frequency. 
     
     
         6 . The monitoring unit of  claim 4  wherein the first signal is a time-invariant voltage and the second signal is a time-varying voltage. 
     
     
         7 . The monitoring unit of  claim 1  further comprising:
 an alarm coupled to the processor, wherein the processor is configured to activate the alarm in response to the detection circuit outputting the second signal. 
 
     
     
         8 . The monitoring unit of  claim 7  further comprising:
 a first probe assembly operably arranged in a first container of a first product, the first probe having a low impedance state when in contact with the first product and a high impedance state when not in contact with the first product, the first probe assembly coupled to a first electrical input port of the plurality of electrical input ports; and 
 a second probe assembly operably arranged in a second container of a second product, the second probe assembly having the low impedance when in contact with the second product and the high impedance when not in contact with the second product, the second probe assembly coupled to a second electrical input port of the plurality of electrical input ports. 
 
     
     
         9 . The monitoring unit of  claim 8  wherein the processor selectively couples the first electrical input port and the second electrical input port to the detection circuit so that the first probe assembly and the second probe assembly are individually coupled to the detection circuit in a repeating sequence. 
     
     
         10 . The monitoring unit of  claim 9  wherein the processor does not activate the alarm unless the same electrical input port provides the high impedance to the detection circuit during two or more consecutive couplings. 
     
     
         11 . A method of monitoring a level of a product in a dispensing system, the method comprising:
 causing, by a processor, a switch matrix to selectively couple a plurality of electrical input ports of the switch matrix to an input of a detection circuit;   in response to detecting a low impedance at the input, outputting a first signal at an output of the detection circuit; and   in response to detecting a high impedance at the input, outputting a second signal at the output of the detection circuit.   
     
     
         12 . The method of  claim 11  further comprising:
 polling each electrical input port; and 
 flagging each electrical input port for monitoring that presents the low impedance. 
 
     
     
         13 . The method of  claim 12  wherein selectively coupling the plurality of electrical input ports of the switch matrix to the input of the detection circuit comprises:
 sequentially coupling each flagged electrical input port to the input for monitoring by the detection circuit. 
 
     
     
         14 . The method of  claim 11  wherein the first signal is a time-varying voltage at a first frequency and the second signal is a time-varying voltage at a second frequency. 
     
     
         15 . The method of  claim 11  wherein the first signal is a time-invariant voltage and the second signal is a time-varying voltage. 
     
     
         16 . The method of  claim 11  further comprising:
 activating an alarm in response to the detection circuit outputting the second signal. 
 
     
     
         17 . The method of  claim 11  further comprising:
 coupling a first probe assembly to a first electrical input port of the plurality of electrical input ports, the first probe assembly operably arranged in a first container and having a low impedance state when in contact with a first product in the first container and a high impedance state when not in contact with the first product; and 
 coupling a second probe assembly to a second electrical input port of the plurality of electrical input ports, the second probe assembly operably arranged in a second container and having the low impedance state when in contact with a second product in the second container and the high impedance state when not in contact with the second product. 
 
     
     
         18 . The method of  claim 17  wherein further comprising:
 selectively coupling the first electrical input port and the second electrical input port to the detection circuit so that the first probe assembly and the second probe assembly are individually coupled to the detection circuit in a repeating sequence. 
 
     
     
         19 . The method of  claim 18  wherein the alarm is not activated unless the same electrical input port provides the high impedance to the detection circuit during two or more consecutive couplings. 
     
     
         20 . A computer program product comprising:
 a non-transitory computer-readable storage medium; and   program code stored on the non-transitory computer-readable storage medium that, when executed by a processor of a monitoring unit, causes the monitoring unit to:   selectively couple a plurality of electrical input ports of a switch matrix to an input of a detection circuit;   in response to detecting a low impedance at the input, output a first signal at an output of the detection circuit; and   in response to detecting a high impedance at the input, output a second signal at the output of the detection circuit.