IES65853B2 - Temperature monitoring apparatus - Google Patents

Abstract

A temperature monitoring apparatus is described trypically adapted to monitor the temperature in the refrigerated compartment of a transportable refrigeration unit. The apparatus comprises at least one temperature sensor, a microprocessor device and a memory storage device of ideally 128Kb RAM wherein the microprocessor is programmed to record a temperature value in response to information from the temperature sensor at predetermined time intervals, e.g. every 15 minutes, in accordance with a data compression algorithm such that data records including date, time, temperature and event data in ASCII format are identified by means of an 8-bit record identifier. Preferably, at least two temperature sensors are provided, for example to monitor cold exhaust air entering the refrigerated compartment and warmer air beig returned to the associated refrigerator unit. Also, at least two event switches are provided, for example to monitor the opening and closing of the access doors to the refrigerated compartment, and to monitor the activation of a defrost switch in the refrigerator unit.

Description

The present invention relates to temperature monitoring apparatus, and in particular to an apparatus and method for logging the temperature over a period of time in refrigerated vehicles and trailers.

Operators of refrigerated transport systems for transporting perishable food products are required by legislation to keep a log of the ambient, temperature .in:refrigerated..units, for a.period..of at -least.. twelve months. This log may be used by the transport operators or regulatory authorities to determine when and where a critical temperature variation may have occurred which might cause damage to the food products in transport. It is now a requirement to keep a log of at least twelve months* historic data.

The onus is on the transport operator to ensure that the optimum temperature or temperature range is maintained within the refrigerated unit during the entire journey.

Traditionally, pen chart recorders have been used, for example recording a week or month of elapsed time on a single sheet, but pen chart recorders are sensitive mechanical instruments which 1508S - 2 require regular maintenance and special graph paper. Another practical problem is that the driver of the vehicle cannot readily make multiple copies of the temperature graph at various delivery points.

Microprocessor-based temperature monitoring systems are now more widely in use which have added features, such as monitoring both the exhaust air and the return air as well as the defrost switch in the refrigeration unit. A sensor may also be used to monitor the times at which the access door to the refrigeration unit is opened. Periodic temperature measurements may be stored electronically on a memory chip, but typically the amount of data for a twelve months* period would occupy in excess of 150 Kb of random access memory (RAM). However, standard RAM chip sizes are 128 Kb or 256 Kb, with the latter being considerably more expensive. An on-board portable computer and printer may be used to print-out a log at any location, and information logged over a period of time may be downloaded into a computer belonging to the transport operator or a regulatory authority. However, since the present requirements are that the logged data must be accessible for a period of at least twelve months, the on-board logging apparatus must have an internal memory capacity capable of storing at least twelve months data, or else a reliable printer has to be used so that data can be printed-out on demand so that the required log can be kept; It will be appreciated that on-board printers may not be sufficiently reliable and that technical support and servicing may not be available during a journey. Paper records are also easily lost.

For this reason it is preferable to store all data for the required twelve-months* period electronically in the memory of the on-board temperature monitoring apparatus. For this to be achieved at reasonable cost, it would be desirable to use a 128Kb RAM chip.

It should also be borne in mind that the temperature monitoring apparatus is normally located on the exterior of a refrigeration unit such as a refrigerated trailer so that it must be of rugged construction with the minimum of servicable parts.

The present invention provides a temperature monitoring apparatus comprising at least one temperature sensor, a microprocessor - 3 device and a memory storage device wherein the microprocessor is programmed to record a temperature value in response to information from the temperature sensor at predetermined time intervals in accordance with a data compression algorithm such that data records including date, time, temperature and event data in ASCII format are identified by means of an 8-bit record identifier.

The apparatus is preferably adapted to monitor the temperature in a transportable refrigeration unit, wherein at least two temperature sensors are advantageously provided, for example to monitor cold exhaust air entering a refrigerated compartment and warmer air being returned to the refrigerator unit. The apparatus is preferably adapted to support at least two event switches, for example to monitor the opening and closing of the access doors to the refrigerated compartment, and to monitor the activation of a defrost switch in the refigerator unit.

Preferably the predetermined time interval is approximately fifteen minutes, wherein the memory comprises 128 Kb RAM, capable of storing recorded temperature data logged over a period of at least twelve months, and preferably thirteen months.

A preferred embodiment of a temperature monitoring apparatus for a refrigerated vehicle will be described with reference to the accompanying drawings in which Figure 1 is a schematic diagram of a typical refrigerated vehicle, Figure 2 is a schematic diagram of the refrigeration unit shown in Figure 1, in slightly more detail, Figure 3 is a schematic diagram of a microprocessor-based temperature monitoring apparatus in accordance with the present invention.

Figure 1 shows a typical refrigeration vehicle comprising a. cab 1, a trailer 2 and refrigerator unit 3 exhausts cold air through inlet 4 to the refrigerated compartment 5 in the trailer, and warmer - 4 air is returned through outlet 6 to the refrigerator unit. Figure 2 shows that the flow of air in the refrigerator unit 3 is controlled by a control unit 7. A defrost switch 8 is attached to the control unit to defrost the refrigerated compartment, when required. The operator 5 may set the desired temperature by means of a thermostatic control 9. Figure 3 shows a microprocessor-based temperature monitoring system in accordance with the present invention and used in conjunction with the control unit. A user-configurable and programmable microprocessor 10, the functioning of which need not be described in detail, includes a 10 memory device 11, preferably of 128 Kb RAM. Temperature sensor 12 monitors the temperature of cold exhaust air from the refrigerated compartment 5 and temperature sensor 13 monitors the temperature of Event switch 14 and event switch 15 to the refrigerated provided for optional a printer 19. The At specific intervals it stores the values of these inputs into the memory device. At a 20 delivery point, the operator can give a print-out of the logged data on temperature and other events during a journey to the customer. At a future date, the‘operator can copy all 'historical .data from the apparatus to a PC for further analysis and/or storage.

The compression algorithm and memory format used by the system will be described in further detail. return air from the refrigerated compartment, monitors the activation of the defrost switch 15 monitors the times when the main access doors compartment are opened. Ports 16 and 17 are connection to a personal computer 18 (PC) and microprocessor monitors the various inputs.

The microprocessor can preferably handle two event switches and two probes. From a recording point, temperature is stored in whole degrees. Also it should be noted that the memory storage specification has the capability of supporting four temperature probes and three switches.

The capacity of the memory, in terms of logged events, .is dependent on the logging interval. Assuming a 15-minute interval: 32k RAM > 3 Months 128k RAM > 13 Months - 5 512k RAM > 53 Months At each logging time, either Minimum, Mean or Maximum values are stored. This is user-configurable.

A record comprises a control character followed by one or more data characters. The control character has bit (7) set on, data characters have bit (7) set off.

CONTROL CHAR: (7, 6, 5) These three bits are the record identifier. 100 Special Record 101 Date Record 110 Time Record 111 Data Record The remaining bits (4, 3, 2, 1, 0) only have meaning for a type 111 (Data) character and for type 100 (Special) character.

Ill Data Record (4, 3, 2) Switch status. Thus, we can.showup to three different switches. (1, 0) Number of probe characters to follow. Since a value of 0, denotes 1 we can have a maximum of 4 probe characters. 100 Special Record 1000000 This is a Power-Up/Start-Trip character, it has no additional data characters. It is generated at a COLD START only.

If the system restarts due to a software interrupt, this record is NOT generated. 1000001 This is a Device-ID-Start character, it is used within the - 6 RAMDISK system to delimit data from different temperature monitoring units in accordance with the invention.

When data is copied by the RAMDISK from the monitoring unit, it prepends a 'Device-ID-Start' character with a 10 character device identifier to the data.

In this instance, there are 10 trailing characters, which define the monitoring unit identifier from which the data was extracted. 81, 81, 81, xxxxxxxxxx, dd...., 82,82, 82 15 where the dd....dd is the data that was copied from a vehicle with an identifier of xxxxxxxxxx NOTE: We use three 81’s and also three 82's to delimit the block. This is done for clarity and simplicity to ensure that device block delimiters are easily recognised. 10000010 This is a Device-ID-End character, it is used within the RAMDISK system to delimit data from different monitoring units.

When data is copied by the RAMDISK from the monitoring apparatus, it appends a 'Device-ID-End' record to the data. In the above example YY has been appended to the data. If anything aborted the uploading of data, then-the 82 character .would be missing. - 7 DATE: 2, 3 4, 5 6, 7, 8, 9 . 11 12, 13 14 - 17 18, 19 21, 22 23 24, 25 Comprises a date character, followed by 19 data characters. Each character is coded in ASCII, this is to ensure that the high order bit never gets set.

Data Character Day of Month in ASCII (Yesterday) Month Number in ASCII (Yesterday) Year (full) as 4 ASCII characters (Yesterday) Day of Month in ASCII (Today) Month Number in ASCII (Today) Year (full) as 4 ASCII characters (Today) Logging interval in minutes (ASCII). A value of '0' denotes that an unknown error has occured and the time interval for the data cannot be ascertained, a ·+' or character The bias value as in parameter 020 Reason for the Date Record Change at Midnight RTC Change Parameter Change Power Up Warm Software Restart Data was Cleared Parameter Number that was changed. Only valid if character position 22 is set to 3.

TIME: Comprises a time character, followed by 4 data characters.

Each character is coded in ASCII, this is to ensure that the - 8 high order bit never get set. time Character 2, 3 Hours of the day in 24 hour format, ASCII 4, 5 Minutes of the hour, in ASCII format DATA: The data record comprises the start DATA character as defined previously. There will then be further data characters dependent on the setting of bits 1,0 as follows: additional additional additional 4 additional data character data characters data characters data characters The format of these additional data characters is as shown below: Bit (7) Must Be Zero (6) .Must,be 1. ...This ensures that we never have a character less than 32 which are the ASCII Control characters. (5-0) Amount as 0-64 Thus we can handle values in the range 0 to +64. In order to handle other values, we have to modify the reading so that it can still fall into the +64 degree span. Parameter 020 is used to define the bias. If we wanted to handle temperatures in the range -34 to +30, then we would set parameter 20 to +34. All temperature readings have P020 ADDED prior to storage, and must have P020 SUBTRACTED after extraction from memory.

Assuming that we log every 15 minutes, this, means..that there . would be 96 loggings per day. Every day we log the date, so the total memory overhead per day is: - 9 23 (Date) + 3*96 (Data) = 301 characters At 31 days per month, we need 9331 characters per month plus an additional 24 characters per start round record.

With the above format of records and characters, we ensure that the data transmitted does not affect the standard ASCII control characters like CR, LF, XON and XOFF etc.

Occurence of Records: POWER-UP/START-TRIP This record is generated: When the system enters the powered-on state from a powered-off state.

When all the data in the logging memory is deleted by a remote communications command.

The internal print routine uses this record as a delimiter for trips when using MODE-2 printing.

DATE This record is, generated:...

After a POWER-UP/START-TRIP record is generated.

- After a warm restart.

When parameters 001, 002, 003, 009, 018, 020, 021, 022, 023 or 024 are set through the communications interface.

When the date and/or time in the real time clock is set through the communications interface or through the power-up keypad menu.

At midnight. NOTE: There is no guarantee that, this record will actually be generated at midnight.

It will be generated when the system is in idle mode, at the earliest opportunity after midnight. The time record immediately after the date record will show the actual time of the logging.

- When transaction data is cleared.

TIME This record is generated: - Any time that the DATE record is generated.

During EVENT-LOGGING, at every logging event.

DATA This record, also called a probe record, is generated: When time logging, every time that the logging timer reaches its required count in seconds. The count value is stored in parameter 002. It should be noted that this timer continually counts up to this value, generates the record and starts the count again. If a DATE, TIME or POWER-UP record is generated, this time is automatically restarted at zero, thus losing whatever partial count it may have accumulated.

- When event logging, this record is generated, along with.a TIME -record whenever a probe/switch crosses a boundary from one band to another. See parameters 021, 022 and 023.

If there is a long communications session, for example reading or printing transactions, there is a possibility that the unit may not be able to log data in real time. This is a definite possibility when short logging intervals (1 minute) are being used. When this happens, the unit generates filler records when the transaction file is again free. The probe and switch values will be based on the actual readings when the logging is eventually performed.

Claims (4)

1. A temperature monitoring apparatus comprising at least one 5 temperature sensor, a microprocessor device and a memory storage device wherein the microprocessor is programmed to record a temperature value in response to information from the temperature sensor at predetermined time intervals in accordance with a data compression algorithm such that data records including date, time, temperature and event data in 10 ASCII format are identified by means of an 8-bit record identifier.

2. A temperature monitoring apparatus according to claim 1 adapted to monitor the temperature in the refigerated compartment of a transportable refrigeration unit, wherein at least two temperature 15 sensors are provided, for example to monitor cold exhaust air entering the refrigerated compartment and warmer air being returned to the associated refrigerator unit.

3. A temperature monitoring apparatus according to claim 1 or claim 20 2, additionally adapted to support at least two event switches, for example to monitor the opening and closing of the access doors to the refrigerated compartment, and to monitor the activation of a defrost switch in the refigerator unit. 25 4. A temperature monitoring apparatus according to any of claims 1 to 3, wherein the predetermined time interval is approximately fifteen minutes, wherein the memory comprises 128 Kb RAM, capable of, storing recorded temperature data logged over a period of at least twelve months, and preferably thirteen months. 5. A temperature monitoring apparatus according to any of claims 1 to

4. , substantially as described herein with reference to and as shown in the accompanying drawings.