SYSTEM, APPARATUS, AND METHOD FOR ICE DETECTION

Abstract

A system, apparatus, and method for determining when an amount of ice formed on an evaporator or evaporator grid has reached a predetermined size are illustrated. An acoustic transmitter an acoustic transmitter positioned proximate to the evaporator channels acoustic signals emanating from the evaporator or evaporator grid to an acoustic sensor, which generates an electronic signal indicative of the acoustic signal. A receiver module coupled to the acoustic sensor is configured to receive the electronic signal and determine that ice formed on the evaporator has reached a predetermined size based on the electronic signal.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 61/441157, filed on Feb. 9, 2011, and incorporated herein by reference.

FIELD

The present disclosure relates to a system, apparatus, and method for detecting an object or the lack of the presence of an object, including the detection of ice in an ice-forming apparatus or refrigeration case or system.

BACKGROUND

This section provides background information related to the present disclosure and is not necessarily prior art.

In some ice-forming apparatuses, ice is formed from an evaporator grid. The ice grows on the evaporator grid until it reaches a desirable size or thickness. Once the ice has reached the desired size or thickness, the ice is harvested from the evaporator grid, thereby separating ice cubes from the evaporator grid. The ice-forming apparatus determines when to harvest the ice, i.e., the harvest initiation point.

One technique determines water conductivity. For example, an electrode or probe may be placed a precise distance away from the evaporator. As the ice forms, the water flowing over the evaporator eventually comes in contact with the probe. A conductive path via the water is formed between the electrode and the chassis of the machine (ground), thereby indicating that the ice has reached a predetermined size. These types of sensors, however, have certain drawbacks. For instance, as scale forms on the probe, a parallel conductive path can be formed to ground. Furthermore, extremely pure water is not conductive, thereby reducing the effectiveness of the sensor.

Another technique may utilize capacitive sensors. For example, an electrode may be placed a precise distance away from the evaporator. As the ice forms, the water flowing over the evaporator eventually comes in contact with the probe. When the water comes in contact with the electrode, the capacitance changes and this change can be used to determine the harvest initiation point. Capacitive sensors used in this setting also suffer from certain drawbacks. For instance, scaling can interfere with the capacitance reading when dirty water is used in the ice-forming apparatus.

A third technique is a batch system technique. For example, in a batch system the water level in a sump tank may be measured. The sump is filled to a predetermined point and then the pump is started and the ice starts to form. As ice forms, the level in the sump decreases. When the water level decreases to a sufficient level the harvest is initiated. A draw back with this technique is that the ice thickness may vary due to factors such as environmental conditions (temperature, humidity), level of total dissolved solids in the water (only the water freezes, not the minerals), and water loss in the sump (e.g., a leaking water dump valve). Thus, the batch system technique may not result in uniformly sized ice cubes from batch to batch.

SUMMARY

In an aspect of the disclosure, a system for determining when an amount of ice formed on an evaporator has reached a predetermined size is illustrated. The system includes an acoustic transmitter positioned proximate to the evaporator and an acoustic sensor coupled to the acoustic transmitter. The acoustic transmitter channels acoustic signals emanating from the evaporator to the acoustic sensor and the acoustic sensor generates an electronic signal indicative of the acoustic signal. The system further includes a receiver module coupled to the acoustic sensor and configured to receive the electronic signal, and determine that ice formed on the evaporator has reached a predetermined size based on the electronic signal.

In another aspect of the disclosure, an ice-forming apparatus is disclosed. The apparatus includes an evaporator grid, an acoustic transmitter positioned proximate to the evaporator grid, and an acoustic sensor coupled to the acoustic transmitter. The acoustic transmitter channels acoustic signals emanating from the evaporator grid to the acoustic sensor and the acoustic sensor generates an electronic signal indicative of the acoustic signal. The apparatus further includes a receiver module coupled to the acoustic sensor and configured to receive the electronic signal, and determine that ice formed on the evaporator grid has reached a predetermined size based on the electronic signal.

In another aspect of the disclosure, a method for determining whether formed ice has reached a predetermined size is disclosed. The method includes receiving an electronic signal indicative of an acoustic signal, transforming the electronic signal from a time domain to a frequency domain, sampling one or more amplitudes of the transformed signal at one or more predetermined frequencies, and initiating one of a harvest operation and a defrost cycle based on the one or more sampled amplitudes.

Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is a drawing illustrating exemplary machinery of an ice-forming apparatus having an acoustical sensor system according to various embodiments of the disclosure;

FIGS. 2A and 2B are drawings illustrating an exemplary acoustic transmitter in an assembled view and in an exploded view, respectively, according to various embodiments of the disclosure;

FIG. 3 is a drawing illustrating an exemplary acoustic transmitter in an assembled view according to various embodiments of the disclosure;

FIG. 4 is a drawing illustrating an exemplary acoustic sensor system according to various embodiments of the disclosure; and

FIG. 5 is a flow chart illustrating an exemplary method for determining when formed ice has reached a predetermined size according to various embodiments of the disclosure.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings.

The current disclosure describes an apparatus that enables detection of objects or material (collectively, an “object” or “objects”). Examples of objects, articles, or material which may be detected by the apparatus and method include, but are not limited to, solid objects or material such as ice. Examples of object- or material-processing systems include, but are not limited to ice-forming machines and ice-collection bins of ice-making systems. Other example applications may include refrigeration cases, bins, freezers, display cases, and other devices or refrigeration storage containers, where the detection system may be used to detect an accumulation of ice and initiate a defrost procedure.

FIG. 1 illustrates an exemplary ice-forming apparatus 100. An exemplary ice-forming apparatus 100 can include an evaporator 110, an acoustic transmitter 120 that transmits acoustic signals, a receiver module 130, and a flexible acoustical transmission tube 140 that channels the acoustic signals from the acoustic transmitter 120 to the receiver module 130. The receiver module 130 processes electronic signals corresponding to the acoustic signals and controls the evaporator 110 based thereon.

In an exemplary embodiment, the evaporator 110 can include an evaporator grid 160, an evaporator coil (not shown) and a cold plate (not shown). The evaporator grid 160 is used to form ice cubes. Water is pumped from a water reservoir (not shown) onto the cold plate, which is maintained at a temperature below a freezing temperature, e.g., less than thirty-two (32) degrees Fahrenheit or zero (0) degrees Celsius. The evaporator grid 160 can be formed in the shape of the ice that is to be harvested from the evaporator grid 160, e.g., a cubic or rectangular prism. When the ice has a desired depth or thickness, the ice can be harvested using known techniques. For instance, the evaporator grid 160 may be heated such that the formed ice cubes break and separate from the evaporator grid 160.

The ice-forming apparatus 100 shown in FIG. 1 can be a vertical ice-forming apparatus 100, wherein water flows from the top of the vertical ice-forming apparatus 100 over a vertical evaporator grid 160. It is appreciated that the techniques disclosed herein may be applied to any other type of ice-forming apparatuses 100 or to any other types of apparatus that incorporates an evaporator 110, e.g., a refrigeration apparatus and an air conditioner.

The receiver module 130 controls whether the evaporator 110 is forming ice or harvesting ice. When the formed ice has reached a sufficient size or thickness, the receiver module 130 initiates a harvesting operation, e.g., instructs the evaporator 110 to heat the evaporator grid 160 to harvest the ice. The receiver module 130 can be configured to receive electronic signals indicative of the acoustic signals channeled from the acoustic transmitter 120. As described in further detail below, an acoustic sensor can receive an acoustic signal and generate the electronic signal corresponding to the acoustic signal. The acoustic signal (and the electronic signal) can provide an indication of the size of the formed ice, e.g. the depth or thickness of the formed ice.

In some embodiments, the receiver module 130 processes the electronic signal received from the acoustic sensor to sample the amplitude of the electronic signal at certain predetermined frequencies. When the amplitude of the electronic signal at the predetermined frequencies (or a subset of the predetermined frequencies) exceeds corresponding predetermined thresholds, the receiver module 130 determines that the formed ice has reached sufficient size or thickness and initiates a harvesting operation. In other words, when the amplitude of the acoustic signals at the predetermined frequencies (or a subset of the predetermined frequencies) exceeds the corresponding predetermined thresholds, the receiver module 130 determines that the harvest initiation point has been reached and initiates the harvest.

The acoustic transmitter 120 can be positioned in proximity to the evaporator grid 160. The focal points of the diaphragm of the acoustic transmitter, discussed in greater detail below, can be positioned to face the evaporator grid 160. The acoustic transmitter 120 may pick up and transmit the background noise or frequencies of the ice-forming apparatus 100, or other device or machinery within which it is installed. As the ice grows, the ice can form and grow towards the acoustic transmitter 120. Once the ice physically touches the acoustic transmitter 120, there is a significant increase in the amplitude of the noise signal generated by the ice-forming apparatus 100, e.g., noise resulting from mechanical vibration from the ice-forming apparatus 100. When there is no physical contact between the acoustic transmitter 120 and the ice formed on the evaporator grid 160 100, the noise emanating from the ice-forming apparatus 100 is transferred via the air and the amplitude of the noise signal is reduced. The acoustic signals that are picked up by the acoustic transmitter 120 can be transferred to an acoustic sensor (not shown) via the flexible acoustical transmission tube 140.

In some embodiments, the acoustic transmitter 140 can be used to measure the “bridge thickness” of the ice. The diaphragm of the acoustic transmitter 120 can be placed relatively close to the evaporator grid 160, e.g., one-eight (⅛) of an inch, so as to measure the bridge thickness. The bridge thickness is indicative of the overall depth or thickness of the formed ice.

In some embodiments, a wall 150 can separate the receiver module 130 and other electronics from the evaporator 110. As will be discussed in further detail, an acoustic sensor, e.g., a microphone, can be located at the evaporator grid 160 side of the wall 150, or at the receiver module 130, such that the acoustic signal is transferred to the acoustic sensor via the flexible acoustical transmission tube 140.

In some embodiments, the acoustic transmitter 120 may be placed proximate to an evaporator 110 of a refrigeration case, a refrigeration bin, a freezer, a refrigeration display case, and other types of refrigerated storage containers. In these embodiments, the acoustic transmitter 120 can be positioned near an area of the evaporator 110 where ice typically accumulates, e.g., the fins of the evaporator 110, so that the receiver module 130 can determine whether the accumulated ice has exceeded a predetermined level. When the receiver module 130 determines that the accumulated ice has exceeded the predetermined level, the receiver module 130 can initiate a defrost operation, such as commencing a defrost cycle.

FIGS. 2A and 2B illustrate an exemplary acoustic transmitter 120 in an assembled view and an exploded view, respectively. In some embodiments, the acoustic transmitter 120 can include an acoustic transmitter frame 210, an acoustic diaphragm 220, a flexible acoustical transmission tube 140, an interface 240 that couples the flexible acoustical transmission tube 140 to the acoustic diaphragm 220, and a height-adjustment screw 250.

In some embodiments, the acoustic transmitter 120 includes the acoustic transmitter frame 210 and the acoustic diaphragm 220. The acoustic transmitter frame 210 can include a substantially circular portion that forms an acoustical chamber 260. The substantially circular portion receives the acoustic diaphragm 220. It should be appreciated that the acoustic chamber 260 can be formed in any suitable shape.

The acoustic diaphragm 220 can be a thin membrane that vibrates when the pressure caused by sound waves is imparted on the acoustic diaphragm 220. The vibration of the acoustic diaphragm 220 causes an acoustic signal, e.g., a sound wave, to reverberate throughout the acoustical chamber 260. The acoustic diaphragm 220 can include a plurality of focal points 230-A and 230-B. The focal points 230-A and 230-B can be positioned facing and substantially parallel to the evaporator grid 160 (FIG. 1).

In some embodiments, the acoustic transmitter frame 210 can include the interface 240, which is configured to receive the flexible acoustical transmission tube 140. The flexible acoustical transmission tube 140 can be forcibly inserted onto or into the interface 240, such that acoustic signals amplified by the acoustic diaphragm 220 are channeled to the acoustic sensor through the flexible acoustical transmission tube 140. As will be discussed in further detail below, the acoustical signals can be received by the acoustic sensor which outputs electrical signals indicative of the acoustic signal to the receiver module 130.

In some embodiments, the acoustic transmitter 120 can include a height-adjustment screw 250. The height-adjustment screw 250 can protrude perpendicularly from the frame 210. The height-adjustment screw 250 can be utilized to adjust a distance between the acoustic transmitter 120 and the evaporator grid 160. As should be appreciated from FIG. 2B, the height-adjustment screw 250 can be inserted into an opening in the frame 210. The height-adjustment screw 250 can be screwed in to increase the distance between the acoustic transmitter 120 and the evaporator grid 160. It should be appreciated that other means for controlling the distance between the acoustic transmitter 120 and the evaporator grid 160 are contemplated and are within the scope of this disclosure.

It should be appreciated that the acoustic transmitter 120 of FIGS. 2A and 2B are provided for example only and not intended to be limiting. Variations of the acoustic transmitter 120 are contemplated and are within the scope of the disclosure.

FIG. 3 illustrates an alternative embodiment of an acoustic transmitter 300. For purposes of explanation, components appearing in the acoustic transmitter 120 of FIGS. 2A and 2B and in the acoustic transmitter 300 of FIG. 3 have been provided the same reference numbers.

In some embodiments, the acoustic transmitter 300 may include an acoustic sensor 270 coupled to the interface 240. In these embodiments, the acoustic sensor 270 can be mounted to the interface 240 such that the acoustic signals emanating from the acoustic diaphragm 220 are channeled directly to the acoustic sensor 270. The acoustic sensor 270 receives the acoustic signal and outputs an electronic signal indicative of the received acoustic signal to the receiver module 130. It should be appreciated that the acoustic sensor 270 can be any suitable microphone. It should be further appreciated that other types of acoustic sensors 270 can be used, such as sound transducers or piezoelectric transducers.

FIG. 4 illustrates an example acoustic transmitter system 400. In some embodiments, the acoustic transmitter system 400 can include the acoustic transmitter 120, the flexible acoustical transmission tube 140, the acoustic sensor 270, the receiver module 130, and a housing 410. As can be appreciated, the exemplary acoustic transmitter 120 described with respect to FIGS. 2A and 2B is connected to the receiver module 130 by the acoustical transmission tube.

In the illustrated example, the receiver module 130 includes an acoustic sensor 270, a circuit board assembly 420, and a receiver clip 430, all of which can be housed in the housing 410. The receiver clip 430 is any suitable fastener that fastens the flexible acoustical transmission tube 140 to the acoustic sensor 270. It is appreciated that other acoustic sensors can be used, such as sound transducers or piezoelectric transducers. The acoustic signals are channeled from the acoustic transmitter 120 to the acoustic sensor 270, which converts the received acoustic signal into an electronic signal that is able to be processed by the receiver module 130, e.g., a digital signal.

As should be appreciated from the illustrated example, the acoustic transmitter 120 can be placed proximate to an evaporator grid 160 (FIG. 1). It should be appreciated that while the acoustic transmitter 120 is explained as being proximate to an evaporator grid 160, the techniques disclosed herein are applicable to any type of evaporator 110. In some embodiments, the acoustic transmitter 120 can be positioned such that the focal points 230-A and 230-B (FIGS. 2A and 2B) of the acoustic diaphragm 220 (FIGS. 2A and 2B) face the evaporator grid 160. The acoustic sensor 270 may be coupled to the acoustic transmitter 120. In the illustrated example, the flexible acoustical transmission tube 140 is interposed between the acoustic transmitter 120 and the acoustic sensor 270. The acoustic transmitter 120 channels acoustic signals emanating from the evaporator grid 160 to the acoustic sensor 270. The acoustic sensor 270 can generate an electronic signal indicative of the acoustic signal, which is provided to the receiver module 130.

The receiver module 130 can be electrically coupled to the acoustic sensor 270 such that the receiver module 130 is configured to receive the electronic signal. The receiver module 130 can be further configured to determine that ice formed on the evaporator grid 160 has reached a predetermined size based on the electronic signal. When the ice formed on the evaporator grid 160 extends from the evaporator grid 160 and physically connects to the acoustic diaphragm 220, amplitude of the acoustic signal transmitted by the acoustic transmitter 120 may increase. Thus, the receiver module 130 can continuously monitor the amplitudes of the electronic signal to determine when to initiate an ice harvesting operation or a defrost operation.

In some embodiments, the receiver module 130 can be configured to transform the electronic signal to a frequency domain and sample one or more amplitudes of the transformed electronic signal at one or more predetermined frequencies. In some of these embodiments, the receiver module 130 can compare each of the one or more sampled amplitudes to a corresponding predetermined amplitude threshold, such that when one or more of the sampled amplitudes exceeds its corresponding predetermined amplitude threshold, the receiver module 130 determines that the ice has reached the predetermined size. In other embodiments, the receiver module 130 can determine that the ice has reached the predetermined size when all of the sampled amplitudes exceed their corresponding predetermined amplitude thresholds.

It is noted that for each ice-forming apparatus 100, refrigeration case, air-conditioner, or the like, the frequencies at which the amplitudes may be sampled are determined during a testing phase. Depending on factors such as the size of the cavity of the ice-forming apparatus 100, the machinery of the ice-forming apparatus 100, or other pertinent factors, such as the compressor operating frequency of the ice-forming apparatus 100, one or more frequencies are determined to be appropriate for sampling. For example, in some embodiments, it may be determined that the amplitudes can be sampled at 60 Hz, 120 Hz, 180 Hz, and 240 Hz.

During the testing phase, the amplitude thresholds for a particular ice-cube size that correspond to the predetermined frequencies are also determined. For instance, for a first frequency, a first amplitude threshold can be determined, for a second frequency, a second amplitude threshold can be determined, etc., to an nth frequency, for which an nth amplitude threshold can be determined. Once the frequencies and thresholds have been determined, the receiver module 130 can be configured to sample the transformed electronic signal at the frequencies and to determine whether the ice is ready for harvesting based on the amplitudes of the electronic signal at the frequencies.

FIG. 5 illustrates an exemplary method 500 that may be executed by the receiver module 130. The method 500 may start executing when the ice-forming apparatus 100 is operating in a freezing mode or when a refrigeration case or system is operating in a cooling cycle. At 510, the receiver module 130 can receive the electronic signal indicative of the acoustic signal from the acoustic sensor 270. At 512, the receiver module 130 can transform the electronic signal to the frequency domain. In some embodiments, a Fast Fourier Transform (FFT) is performed on the electronic signal to transform the electronic signal from the time domain to the frequency domain. It should be appreciated that any suitable transformation technique can be implemented by the receiver module 130. For instance, the receiver module 130 can implement a Discrete Fourier Transform, Laplace Transforms, or Z-Transforms to transform the electronic signal to the frequency domain.

At 514, the receiver module 130 can sample the transformed electronic signal at one or more predetermined frequencies. At 516, the receiver module 130 can compare each of the sampled frequencies to a corresponding frequency threshold. If the amplitudes at a predetermined number of frequencies exceed their respective frequency threshold, the receiver module 130 can determine that the formed ice is of sufficient size and/or thickness. In this scenario, the receiver module 130 can initiate a harvest event or a defrost cycle, as shown at 518. It should be appreciated that in some embodiments, the receiver module 130 may require that all of the sampled amplitudes exceed their respective frequency threshold, or one, two, three, or more amplitudes exceed their respective frequency thresholds. If the receiver module 130 determines that the requisite number of amplitudes exceeding the respective amplitude threshold was not met, the receiver module 130 returns to 510.

It is appreciated that the method 500 provided above has been provided for example only and is not intended to limit the scope of the disclosure. Variations of the method 500 are within the scope of the disclosure.

The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical OR. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure.

As used herein, the term module may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC); an electronic circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. The term module may include memory (shared, dedicated, or group) that stores code executed by the processor.

The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, and/or objects. The term shared, as used above, means that some or all code from multiple modules may be executed using a single (shared) processor. In addition, some or all code from multiple modules may be stored by a single (shared) memory. The term group, as used above, means that some or all code from a single module may be executed using a group of processors. In addition, some or all code from a single module may be stored using a group of memories.

The apparatuses and methods described herein may be implemented by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions that are stored on a non-transitory tangible computer readable medium. The computer programs may also include stored data. Non-limiting examples of the non-transitory tangible computer readable medium are nonvolatile memory, magnetic storage, and optical storage.

Claims

1. A system comprising:

an acoustic transmitter positioned proximate to an evaporator,

an acoustic sensor coupled to the acoustic transmitter, wherein the acoustic transmitter channels acoustic signals emanating from the evaporator to the acoustic sensor and the acoustic sensor generates an electronic signal indicative of the acoustic signal; and

a receiver module coupled to the acoustic sensor and configured to receive the electronic signal and determine that ice formed on the evaporator has reached a predetermined size based on the electronic signal.

2. The system of claim 1, wherein the receiver module is further configured to transform the electronic signal to a frequency domain and sample one or more amplitudes of the transformed electronic signal at one or more predetermined frequencies.

3. The system of claim 2, wherein the receiver module is further configured to compare each of the one or more sampled amplitudes to a corresponding predetermined amplitude threshold, wherein when at least one of the one or more sampled amplitudes exceeds its corresponding predetermined amplitude threshold, the receiver module determines that the ice has reached the predetermined size.

4. The system of claim 2, wherein the receiver module is further configured to compare each of the one or more sampled amplitudes to a corresponding predetermined amplitude threshold and determine that the ice has reached the predetermined size when all of the one or more sampled amplitudes exceed the corresponding predetermined amplitude thresholds.

5. The system of claim 4, wherein the receiver module is further configured to initiate one of a harvesting operation and a defrost operation when the ice has reached the predetermined size.

6. The system of claim 1, wherein the receiver module is further configured to initiate one of a harvest operation and a defrost operation when the ice has reached the predetermined size.

7. The system of claim 1 wherein a diaphragm of the acoustic transmitter is positioned such that a focal point of the diaphragm faces the evaporator, whereby when the ice extends from the evaporator and physically connects to the diaphragm an amplitude of the acoustic signal transmitted by the acoustic transmitter increases.

8. The system of claim 7, further comprising a flexible acoustical transmission tube interposed between the diaphragm of the acoustic transmitter and the acoustic sensor.

9. The system of claim 1, wherein the evaporator includes an evaporator grid, such that the acoustic transmitter is positioned proximate to the evaporator grid.

10. An apparatus comprising:

an acoustic transmitter that channels acoustic signals emanating from an evaporator grid to an acoustic sensor that generates an electronic signal indicative of the acoustic signal; and

a receiver module coupled to the acoustic sensor and configured to receive the electronic signal and determine that ice formed on the evaporator grid has reached a predetermined size based on the electronic signal.

11. The apparatus of claim 10, wherein the receiver module is further configured to transform the electronic signal to a frequency domain and sample one or more amplitudes of the transformed electronic signal at one or more predetermined frequencies.

12. The apparatus of claim 11, wherein the receiver module is further configured to compare each of the one or more sampled amplitudes to a corresponding predetermined amplitude threshold and determines that the ice has reached the predetermined size when at least one of the one or more sampled amplitudes exceeds its corresponding predetermined amplitude threshold.

13. The apparatus of claim 11, wherein the receiver module is further configured to compare each of the one or more sampled amplitudes to a corresponding predetermined amplitude threshold and determine that the ice has reached the predetermined size when all of the one or more sampled amplitudes exceed the corresponding predetermined amplitude thresholds.

14. The apparatus of claim 10, wherein the receiver module is further configured to initiate a harvesting operation when the ice has reached the predetermined size.

15. The apparatus of claim 10 wherein a diaphragm of the acoustic transmitter is positioned such that a focal point of the diaphragm faces the evaporator grid, whereby when the ice extends from the evaporator grid and physically connects to the diaphragm an amplitude of the acoustic signal transmitted by the acoustic transmitter increases.

16. The apparatus of claim 15, further comprising a flexible acoustical transmission tube interposed between the diaphragm of the acoustic transmitter and the acoustic sensor.

17. A method comprising:

receiving an electronic signal indicative of an acoustic signal;

transforming the electronic signal from a time domain to a frequency domain;

sampling one or more amplitudes of the transformed signal at one or more predetermined frequencies; and

initiating one of a harvest operation and a defrost cycle based on the one or more sampled amplitudes.

18. The method of claim 17, further comprising:

comparing each of the one or more sampled amplitudes to a corresponding predetermined amplitude threshold; and

initiating the one of the harvest operation and the defrost cycle when at least one of the one or more sampled amplitudes exceeds its corresponding predetermined amplitude threshold.

19. The method of claim 17, further comprising:

comparing each of the one or more sampled amplitudes to a corresponding predetermined amplitude threshold; and

initiating the one of the harvest operation and the defrost cycle when all of the one or more sampled amplitudes exceeds the corresponding predetermined amplitude thresholds.