AU685896B2

AU685896B2 - A chocolate tempertester

Info

Publication number: AU685896B2
Application number: AU13593/95A
Authority: AU
Inventors: John Aston; Reginald Horton
Original assignee: Cadbury Schweppes Pty Ltd
Current assignee: Mondelez Australia Pty Ltd
Priority date: 1994-03-16
Filing date: 1995-03-03
Publication date: 1998-01-29
Anticipated expiration: 2015-03-03
Also published as: AU1359395A

Description

AUSTRAL IA Patents Act 1990 COMPLETE SPECIFICATION~ STANDARD PATENT C C

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Applicant(s): CADBURY SCHWEPPES PROPRIETARY LIMITED A.C.N. 004 551 473 Invention Title: A CHOCOLATE TEMPERTESTER The following statement is a full description of this invention, including the best method of performing it known to me/us:

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2 A CHOCOLATE TEMPERTESTER This invention relates to a chocolate tempertester.

Chocolate tempertesters are devices which estimate the concentration of desirable fat crystals present in chocolate by interpretation of changes in the rate of temperature decrease of a sample as it cools in a cooling chamber under controlled conditions. Conventional chocolate tempertesters plot a cooling curve and the shape of the cooling curve, in particular the slope of a line at the position of inflection, gives a good indication as to whether chocolate has been correctly tempered. In existing chocolate tempertesters, the cooling curve is printed on a strip chart recorder and the operator is required to manually assess the degree of temper by interpreting the 15 shape of the curve.

Thus, convention devices rely heavily on visual interpretation by an operator and this does result in some operator error.

The object of this invention is to provide a chocolate tempertester which can provide a better indication of whether chocolate has been correctly tempered.

The invention may be said to reside in a chocolate tempertester including: temperature sensing means for sensing the temperature decrease of a chocolate sample as the sample cools and for producing an output signal indicative of the temperature decrease of the chocolate sample; processing means for receiving the output signal and for producing a cooling curve from the output signal and for determining the slope of a line at a position of inflection of the cooling curve and for determining whether the slope of the line falls within a predetermined range; I L r -3and display means for displaying information indicative of whether the slope of the line falls within the predetermined range or whether it does not fall within the predetermined range to thereby provide a indication of whether the chocolate has been correctly tempered.

Since the invention actually determines the slope of the line at the position of inflection based on the output signal from the temperature sensor and displays information as to whether the slope is within the predetermined range, an operator can immediately see without any need for interpretation on his or her part, whether the chocolate has been correctly tempered and if not, can adjust the 1 operating parameters of the production equipment accordingly.

Preferably the processing means comprises a temperature acquisition module which receives the output signal from the temperature sensing means and converts the signal into a computer readable signal indicative of the cooling curve, 20 and a computer coupled to the temperature acquisition module, for determining the slope of the line and S•determining whether the slope falls within the predetermined range.

In alternative embodiments the temperature acquisition module and computer may be combined into a single circuit.

Preferably the display means is a screen associated with the computer.

Preferably the temperature acquisition module includes an offset drift circuit for compensating for temperature drift of the acquisition module.

Preferably the temperature acquisition module includes: s IC _II_ -4an amplifier for receiving the output signal and amplifying the output signal by a predetermined factor; a digital to analog converter for converting the output signal to produce a converted output signal; and a microcontroller for receiving the converted output signal and for supplying the computer readable converted output signal to the computer.

Preferably the acquisition module further includes a second analog to digital converter for producing a reference value which is supplied together with the output signal to the first mentioned analog to digital converter to produce the converted output signal.

Preferably the said drift circuit comprises: .'.means for disconnecting the temperature module 15 from the temperature sensing means so that the output signal is not processed by the temperature acquisition module; means for outputting a reference signal; means for receiving the reference signal so that S: 20 the temperature acquisition module processes that reference signal and produces an output reference signal; means for determining whether the output reference signal is greater or less than a predetermined value; and means responsive to the determining means for increasing or decreasing the reference value used during processing of the output signal to compensate for temperature drift, Preferably the means for determining and the means for increasing or decreasing comprise the microcontroller.

Preferably the measuring means is coupled to the amplifier via a bridge circuit and the disconnecting means comprise a first switching element, the switching element being i ~pl coupled to the microcontroller for selectively allowing the output signal from the measuring means to be received by the amplifier or for switching off the output signal, and a second switching element for supplying the predetermined signal to the amplifier.

Preferably the switching elements comprise transistors.

The preferred embodiment of the invention also includes a temperature acquisition circuit for a chocolate tempertester, the temperature acquisition module being for receiving an output signal from a temperature sensor and for converting the output signal into a form readable by a computer, the acquisition circuit including: an amplifier for receiving the output signal and amplifying the output signal by a predetermined factor; converter means for receiving the output signal and a reference value for producing a converted output signal; a controller for receiving the converted output signal and for supplying a computer readable converted output signal to the computer; and offset drift circuit for compensating for oo V.0 temperature drift of the acquisition module.

e Preferably the drift circuit comprises: means for outputting a reference signal; means for receiving the reference signal so that the temperature acquisition module processes that reference 30 signal and produces an output reference signal; means for determining whether the output reference signal is greater or less than a predetermined value; and means for increasing or decreasing the reference value used during processing of the output signal to compensate for temperature drift.

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6 Preferably the reference signal is a zero volt reference signal.

Preferably the means for determining and the means for increasing or decreasing comprise the controller.

Preferably the offset drift circuit also includes means for disconnecting the temperature module from the temperature sensing means so that the output signal is not processed by the temperature acquisition module.

Preferably the disconnecting means comprises a first switching element, the switching element being coupled to the microncontroller for selectively allowing the output signal from the measuring means to be received by the amplifier or for switching off the output signal, and a second switching element for supplying the predetermined signal to the amplifier.

Preferably the switching elements comprise transistors.

The preferred embodiment of the invention also includes a cooling chamber for cooling a chocolate sample including: a container body; 25 a cooling tube supported in the container body; eo o a sample chamber in the cooling tube; means for locating temperature probe in the cooling tube and projecting into the sample chamber so that the probe is located centrally in the sample chamber; and means for maintaining a cooling liquid level at a predetermined level within the container.

Preferably the means for locating the temperature probe comprises a probe support housing locatable on the tube, the support housing having a central hole for receiving the temperature probe.

~sl LII~-- 7 Preferably the means for maintaining the liquid level comprises a drain opening in the container.

Preferred embodiments of the invention will be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a scheaatic view of a chocolate tempertester embodying the invention; Figure 2A is a circuit diagram of a first part of a temperature acquisition module which presents a signal to a computer for analysis; Figure 2B is a circuit diagram of a second part of the temperature acquisition module; Figures 3A, 3B and 3C are a flow chart setting out the operation of the temperature acquisition module and 15 a computer which analyses the temperature data provided by the acquisition module; Figure 4 is a view of a cooling chamber with which the tempertester of Figures 1, 2A and 2B is used; Figure 5 is a detailed view of part of the chamber of Figure 4; Figure 6 is a schematic view of a chocolate tempertester embodying the invention.

With reference to Figure 1, the general layout of a chocolate tempertester embodying the invention is shown.

The chocolate tempertester comprises a temperature acquisition module 12 which is connectable to a temperature probe 14 via a cable 16. The probe 16 measures the temperature of a chocolate sample held in a sample holder 18, which in turn is immersed in a cooling chamber such as an ice container 20. Thus, the probe 14 provides an indication of the temperature decrease of the chocolate sample as it cools.

The temperature acquisition module is connected to a computer 22 via cable 24 and presents data to the computer 1-- 8 for analysis. The data presented to the computer 22 on cable 24 is in the form of a cooling curve indicative of the manner in which the chocolate sample is cooling in the holder 18. The computer as will be described in greater detail hereinafter, analyses the cooling curve and determines the slope of a line at the position of inflection of the cooling curve. The angle of the line is then compared with predetermined limits. If the angle does fall within predetermined limits, the chocolate is correctly tempered and if not, an appropriate signal can be given indicating that operating parameters of the manufacturing equipment or composition of the chocolate require adjustment in order to ensure that the chocolate is correctly tempered and has the required concentration of desirable fat crystals.

The temperature acquisition module 12 is connected to a power supply 26 (such as a 240 volt AC outlet). The power supply is converted to a 12 volt DC power supply by converter 28 and is supplied to the acquisition module 12 on cable With reference to Figures 2A and 2B which show a detailed circuit diagram of the acquisition module 12, cable connects to DC power jack 32 (see Figure 2B) which has an input voltage range of 8 to 30 volts DC. The input 32 connects to a voltage regulator 34 formed of capacitor capacitor 67, regulator 69, capacitor 71, capacitor 73 and diode 75 to produce an output voltage of 5 volts on line 11 which runs all of the electronics of the circuit 2A and 2B.

The temperature probe 14 is a resistance temperature device and connects via cable 16 to connector 36 (see Figure 2A).

The probe 14 forms one leg of a wheatstone bridge circuit consisting of resistor 21, resistor 31, resistor 29 and variable resistance 38. The bridge circuit is driven by a constant current provided by field effect transistor

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9 operational amplifier 37a and resistor 39a. The bridge circuit gives a differential voltage across its output on lines 38 which is proportional to the temperature sensed by the probe 14. Lines 38 are connected to instrumentation amplifier 23 and supply the resulting temperature proportional differential voltage to the inputs of instrumentation amplifier 23 via a low resistance MOS FET Resistors 29, 31 and variable resistance 33 form a reference which is equal to 0°C. The resistor 21 and the probe 14 form the temperature measurement circuit. The output signal provided on lines 38 is therefore the difference between the reference and the temperature ee measurement circuit and gives a range of 0°C to 50 0

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o 15 The instrumentation amplifier 23 amplifies the temperature proportional voltage by a predetermined factor (for example 439.2) to give an output voltage range of 2 volts on output 40. Resistor 41 is used to set the amplification factor of amplifier 23 and references this output to a 2.5 volt 20 reference provided on line 42 so that its output range is from 2.5 volts to 4.5 volts to bring it up to a measurable voltage range.

The 2.5 volt reference voltage is provided by resistor 37 and diode 43, and a capacitor 39 is provided for noise filtering. This reference voltage is also used by the rest of the circuit where necessary as will be explained hereinafter.

The amplified temperature proportional voltage is supplied on line 40 to analog to digital converter 50. The analog to digital converter 50 is also connected to a programmable reference (namely a second analog to digital converter 104) with a nominal voltage of 2.5 volts on line 13.

i- I i 10 The analog to digital converter 50 measures the voltage difference between the inputs on lines 40 and 13 with a maximum input voltage range of 2 volts, as set by the 2 volt reference provided to the analog to digital converter 50 by line 14 via resistors 45 and 47 and capacitor 49 which provides noise filtering.

The analog to digital converter 50 measures this voltage at a sampling rate of, for example, 7,812.5 time per second and provides a 16 bit digital code in a synchronous serial data format on line 44. Thus, the code on line 44 is proportional to the voltage difference between the voltages presented on lines 13 and 40 to the analog to digital converter 50 which in turn is proportional to the temperature decrease sensed by the probe 14.

An oscillator 46 formed by crystal 48, inverters 53 and resistors 57 and 63 and capacitors 59 and 61. The oscillator 46 is connected to the analog to digital converter 50 by line 52 to clock and operate the analog to digital converter The digital code on line 44 from the analog to digital converter 50 is read by a microcontroller 60. The microcontroller 60 converts the data format of the digital code on line 44 to an asynchronous data format readable by the computer 22. The microcontroller 60 also flashes a light emitting diode 79 which is connected to the microcontroller 60 via resistor 77 and inverter 62.

Illumination of the light emitting diode 79 indicates that the unit is operating.

Oscillator 64 formed by crystal 66, resistor 68 and capacitors 70 and 72 is connected to the microcontroller for clocking and operating the microcontroller 60. A reset circuit 74 formed by diode 76, capacitor 78, resistor and resistor 82 is also coupled to the microcontroller -I i 11 to torm a power on reset circuit for the microcontroller The temperature data is sent by the microcontroller 60 on lines 84 to a level translation circuit 90 consisting of integrated circuit 92 and capacitors 94, 96, 98 and 100, and then to the lines 24 for presentation to computer connector 86 of the computer 22.

The computer 22 therefore receives data via cable 24 and connector 86 and processes that data in accordance with a predetermined program which will be described with reference to the flow chart forming figures 3A, 3B and 3C.

In order to prcvent temperature drift of the measurement device itself, a temperature error compensating circuit is provided in the module 12. In the absence of compensation for temperature drift, a significant error can result because the instrumentation amplifier 23 multiplies the temperature proportional differential voltage by a factor of 439.2.

In order to trim out the offset drift, microcontroller 20 supplies a zero voltage to the instrumentation amplifier 23. If the microcontroller 60 receives a measurement from the analog to digital converter 50 which is greater than or less than 10, then there is a drift error which must be trimmed out.

The drift error is trimmed out in the following manner: The microcontroller 60 initially disconnects the bridge circuit 34 by switching off MOS FET 25 and shorts the inputs to the instrumentation amplifier 23 (ie lines 38) by switching on MOS FET 27.

The microcontroller 60 will then wait for a measurement 12 from the analog to digital converter 50. If the digital code is equal to 10, the microcontroller will switch off MOS FET 27 and switch on MOS FET 25 and return to temperature measurement. Otherwise if the error is positive, the microcontroller 60 will increase the voltage on line 13 to the analog to digital converter 50 until the digital code is equal to 10 or if the error is negative, the microcontroller 60 will decrease the voltage on line 13 until the digital code is equal to To increase and decrease the voltage on the line 13, the microcontroller 60 has control of the programmable reference voltage source provided by amplifier 102, digital to analog converter 104, resistors 106 and 108 and resistors 110 and 112.

15 The microcontroller 60 controls the MOS FETS 25 and 27 and the digital to analog converter 104 by sending out a serial data stream to serial to parallel shift registers 114 and 116. The analog to digital converter 104 is connected to the microcontroller 60 by line 15 and lines 107, 109 and 20 111 are connected to the shift registers 114 and 116, which in turn are connected to the MOS FET 25 and MOS FET 27 for .*"controlling the MOS FET 25 and the MOS FET 27 as described above.

In the embodiment shown in Figures 2A and 2B, data is presented on lines 24 to a serial port of the computer 22.

Alternatively, the data could be presented to a parallel communications port which will connect to the computer 22.

Figures 3A, 3B and 3C will now be described the manner in which software control of the computer 22 takes place to provide a measure of whether the chocolate sample has been correctly tempered.

The system software in the computer 22 initialises

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13 variables and constants to be used by the program and initialises the computer input, at step 120. A test is then made for the presence of an input device as per step 122. If no reply is received within ten seconds, or an incorrect reply is received an appropriate message is displayed and the user is eventually returned to system menu as per step 124. If the correct reply is received within 10 seconds, the computer displays the three main screen elements as per step 126. While waiting, the input device signal is read and converted to a temperature value in degrees centigrade. The temperature reading display is updated as per step 128. If the temperature reading display is less than 270 Celsius (80.60 Fahrenheit) the *system will automatically display the following message on 15 the screen "Chocolate sample temperature too low. Collect another sample and re run test". The system then returns to system menu. If the temperature reading displayed is equal to or greater than 270 Celsius (80.60 Fahrenheit) then the system allows the tempertester to proceed to the 20 next stage. If the user depresses a key to abort reading, an appropriate message is displayed on the screen and the system returns to system menu as per step 130. If a key pressed to start measurement readings, the main measurement loop is commenced as per step 132.

The system then sets the time period variable to 600 milliseconds, sets the reading counter variable to zero and sets the signal value variable to zero as per step 134.

The input device signal is then read and added to the variable signal value as per step 136. If the test time period is not finished the program goes back to step 136.

If the period is finished the system progresses from step 138 to step 140 where the readings are averaged and converted to degrees centigrade (or Fahrenheit if appropriate). Readings are stored in a matrix array and the 3 screen display elements are updated. A test for a user key press is then made at step 142, if the key press 14 is to abort, the system returns to system menu as per step 144 otherwise the system tests for the end of the measurement as per step 146. If the measurement is not completed the program returns to step 134. If the measurement is completed the readings are saved and applied to disc file.

Thus, if the measurement is complete, a temperature cooling curve has now been obtained.

The system then mathematically evaluates the matrix of temperature values (that is the cooling curve) to find a .'00 first deviation point as per step 148. If the deviation 0:0. point is not found, the system displays an appropriate O message on the screen and returns to system menu as per step 150. If the deviation is found, the system moves to 15 step 152 where the matrix is again evaluated to find the second deviation point of the cooling curve. If the deviation is not found, the system returns to step 150. If the second deviation is found, all points between the first and second deviations are stored in a new matrix. The new V, 20 matrix is a mathematical representation of the inflection of the cooling curve (ie the release of latent heat).

The system then moves to step 154 where the representation of the inflection of the cooling curve is smooth to effectively form a straight line. The angle of this line in relation to a theoretical base line is then calculated and compared with a look up table having a number of different angles and associated temper value ratios. The matching temper value ratio is then stored in a temper variable.

The look up table also includes appropriate user messages to be displayed on the computer screen which will advise the operator of whether the chocolate is correctly tempered and what action may be required. Each of the angles in the 1 15 look up table has an appropriate temper value and an appropriate message.

At step 156, the system displays an updated graph with a smooth trace and the temper value and a user message is displayed on the screen. If necessary, an alarm can also be sounded.

Appropriate messages which may be displayed, should the temper value be an acceptable value, are as follows: Very under tempered reading this chocolate is under tempered, take remedial action immediately repeat test; Moderately under tempered reading this chocolate is moderately under tempered, repeat test in one co0 *.."hour; 15 Well tempered reading this chocolate is well

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tempered no action required; Moderately over tempered reading this chocolate is moderately over tempered repeat test in one hour; Very over tempered reading this chocolate is 20 over tempered take remedial action immediately repeat test.

S. 55 If the temper value is outside predetermined limits (ie relates to a value in the look up table which is not acceptable) the following message may be displayed: Reading which is outside temper limits there may be a serious problem with this chocolate take remedial action immediately repeat test.

Step 158 requires a user to acknowledge the message on screen and to input an appropriate command of acknowledgment into the computer. The system then exits the program and returns to system menu.

Figures 4 and 5 show the preferred form of the cooling

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16 chamber which is used with the present invention.

The cooling chamber comprises a container 200 which is generally cylindrical in shape and has an outer wall 202 and an inner wall 204 which tapers inwardly towards the base 206 of the container. Insulation material 208 is provided between the inner wall 202 and outer wall 204.

The container 202 has a screw threaded neck 212 for receiving a lid (not shown).

A disc 214 is located in the upper portion of the container 200. The disc 214 has a central opening 216 into which a cooling tube 218 is located. The cooling tube 218 extends from a position slightly above the disc 214 to a position S•..adjacent the base 206 of the container 200. An internal 220 is located in the cooling tube 218 at a desired 15 position in the cooling tube 218 to define a sample chamber 222.

As is best shown in Figure 5, a temperature probe support housing is provided for supporting temperature probe 14.

The housing 230 is generally of cylindrical shape and has an upper section 231 and a cylindrical wall section 233 *which defines a hollow 235. The upper portion 231 is provided with a central bore 237 which is provided with a tapered opening 239 to facilitate insertion of the temperature probe 14 into the bore 237.

The hollow 235 is dimensioned to neatly sit over the upper end of the tube 218 so that the cylindrical wall section 233 rests on disc 214. The temperature probe 14 is thereby located in the sample chamber 222 and held securely centrally within the chamber 222.

The tube 218 is provided with four holes 239 at its bottom extremity (only one hole being shown) and a single hole 241 just beneath the sample chamber 222.

17 A drain passage 240 is provided in the side wall of the container 200.

In operation ice water is located in the container 200 and the disc 214 and tube 218 are located in place. The drain hole 240 maintains a level of the water at a predetermined height and does not allow the level of the water to exceed the level of the drain. A sample of chocolate is located in the sample holder 222 and the sample holder 222 is positioned in the tube 218. The disc 230 carrying the probe 14 is then located on the supports 224 to support the probe 14 centrally in the sample holder 222.

o The tube 218 acts as a chimney to convey cool air up to the sample holder 222 so that the chocolate in the sample holder cools at a controlled rate and the cooling is monitored by the temperature probe 14 as previously described.

The cooling chamber shown with reference to Figures 4 and always ensures that the chocolate sample is positioned in the same place in the chamber and the water level and tube 218 ensure consistent controlled cooling of the sample in S9** gthe sample holder 222 so that the same controlled cooling of the chocolate sample takes place from test to test.

In the preferred embodiment described with reference to the drawings, a separate acquisition module and computer are provided and which are linked together by the cable 24. In other embodiments and in particular if a hand held device is desired, the acquisition module and computer function can be integrated into a single circuit and housing and a digital display provided for displaying the information.

The invention could also be embodied in a computer card tempertester (see Figure 6) that would contain all components of the Temperature Acquisition Module on a

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18 single board edge connect computer card which would plug into a spare slot inside the computer. This Tempertester would draw its power from the PC and directly interface with the PC Motherboard and hard disk drive etc, via the PC's internal circuitry.

Since modifications within the spirit and scope of the invention may readily be effected by persons skilled within the art, it is to be understood that this invention is not limited to the particular embodiment described by way of example hereinabove.

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Claims

2. The tempertester of claim 1, wherein the processing means comprises a temperature acquisition module 20 which receives the output signal from the temperature sensing means and converts the signal into a computer :readable signal indicative of the cooling curve, and a computer coupled to the temperature acquisition module, for determining the slope of the line and determining whether the slope falls within the predetermined range.
3. The tempertester of claim i, wherein the temperature acquisition module and computer may be combined into a single circuit.
4. The tempertester of any one of claims 1 to 3, wherein the display means is a screen associated with the computer. The tempertester of any one of claims 1 to 4, 'e IqlPIIPIIIISC i 20 wherein the temperature acquisition module includes an offset drift circuit for compensating for temperature drift of the acquisition module.
6. The tempertester of any one of claims 1 to 4, wherein the temperature acquisition module includes: an amplifier for receiving the output signal and amplifying the output signal by a predetermined factor; a digital to analog converter for converting the output signal to produce a converted output signal; and a microcontroller for receiving the converted output signal and for supplying the computer readable converted output signal to the computer.
7. The tempertester of claim 6, wherein the *acquisition module further includes a second analog to 15 d.gital converter for producing a reference value which is supplied together with the output signal to the first mentioned analog to digital converter to produce the converted output signal.
8. The tempertester of claim 5, wherein the said drift circuit comprises: means for disconnecting the temperature module from the temperature sensing means so that the output signal is not processed by the temperature acquisition module; means for outputting a reference signal; means for receiving the reference signal so that the temperature acquisition module processes that reference signal and produces an output reference signal; means for determining whether the output reference signal is greater or less than a predetermined value; and means responsive to the determining means for increasing or decreasing the reference value used during processing of the output signal to compensate for ul-l 21 temperature drift.
9. The tempertester of claim 8, wherein the means for determining and the means for increasing or decreasing comprise the microcontroller. The tempertester of claim 8 or 9, wherein the measuring means is coupled to the amplifier via a bridge circuit and the disconnecting means comprise a first switching element, the switching element being coupled to the microcontroller for selectively allowing the output signal from the measuring means to be received by the amplifier or for switching off the output signal, and a second switching element for supplying the predetermined signal to the amplifier.
11. The tempertester of claim 10, wherein the switching elements comprise transistors.
12. A chocolate tempertester according to claim 1 further including a temperature acquisition module for receiving an output signal from the temperature sensing means and for converting the output signal into a form readable by the processing means, the acquisition circuit including: an amplifier for receiving the output signal and amplifying the output signal by a predetermined factor; converter means for receiving the output signal and a reference value for producing a converted output 30 signal; a controller for receiving the converted output signal and for supplying a computer readable converted output signal to the processing means; and an offset drift circuit for compensating for temperature drift of the acquisition module.
13. The tempertester of claim 12, wherein the drift circuit comprises: 22 means for outputting a reference signal; means for receiving the reference signal so that the temperature acquisition module processes that reference signal and produces an output reference signal; means for determining whether the output reference signal is greater or less than a predetermined value; and means for increasing or decreasing the reference value used during processing of the output signal to compensate for temperature drift. beiPerbeste.r
14. The ±rad± of claim 12 or 13, wherein the reference signal is a zero volt reference signal. bMperbester
15. The -sd.tfc of claim 13, wherein the means for determining and the means for increasing or decreasing 15 comprise the controller. .16. *eM erboeer
16. The aira according to any one of claims 12 to 15, wherein the offset drift circuit also includes means for disconnecting the temperature module from the temperature sensing means so that the output signal is not processed by the temperature acquisition module.
17. The cit of claim 16, wherein the disconnecting means comprises a first switching element, the switching element being coupled to the microcontroller for selectively allowing the output signal from the measuring means to be received by the amplifier or for switching off the output signal, and a second switching element for supplying the predetermined signal to the amplifier.
18. The ir cn t of claim 17, wherein the switching elements comprise transistors. I 23
19. A tempertester according to claim 1 wherein the temperature sensing means is a temperature probe, the tempertester also including a cooling chamber for cooling chocolate sample the cooling chamber including: a container body; a cooling tube supported in the container body; a sample chamber in the cooling tube; means for locating the temperature probe in the cooling tube and projecting into the sample chamber so that the probe is located centrally in the sample chamber; and means for maintaining a cooling liquid level at a predetermined level within the container. The tempertester of claim 19, wherein the means for locating the temperature probe comprises a probe support housing locatable on the tube, the support housing having a central hole for receiving the temperature probe.
21. The tempertester of claim 19, wherein the means for maintaining the liquid level comprises a drain opening in the container.
22. A tempertester substantially as herein before *described with reference to the accompanying drawings. S Dated this 22nd day of October 1997. CADBURY SCHWEPPES PROPRIETARY LIMITED By their Patent Attorneys GRIFFITH HACK 30 Fellows Institute of Patent Attorneys of Australia N ABSTRACT A tempertester is disclosed which has a temperature probe 14 locatable in sample chamber (222) which in turn forms part of a cooling tube (218) arranged in a cooling bucket (20, 200). A processor (12) is coupled to the probe (14) for producing a cooling curve from the output signal from the probe (14) and for determining the slope of a line at a position of inflection of the cooling curve and for determining whether the slope of the line falls within a range. A display such as a computer screen (22) displays information indicative of whether the slope falls within the predetermined range or whether it does not fall within the predetermined range to thereby provide an indication of whether the chocolate has been correctly tempered. S 0 S *eeoc *o 9•