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Temperature monitor and alarm system for cold storage rooms
Short communications Table 2 Units, valid temperature range and maximum deviations as a percentage of the commonly quoted values for saturated water Tableau 2 Unitbs, domaine des tempbratures valable et bcarts maximaux en % des valeurs couramment citbes pour reau ?t l'btat saturk
#f, where this variation increases to 2 9,~.
References l
Parameters for function P
Temperature range (K)
Maximum deviation (%)
pf (kgm 3) cpf (kJ kg- 1 K - 1) kf (W m - t K - t ) /~f (× 10 -6 Pas) hfg (kJ kg- ~)
0-300 0-300 0-300 0-300 1-200
0.131 0.441 0.263 2.017 0.025
2 3 4 5
Eckert, E. R. G., Drake, R. M. Analysis of Heat and Mass Transfer McGraw-Hill Book Co., New York, USA (1972) 777 ASHRAE Handbook of Fundamentals ASHRAE, USA (1981) 6.96.11 MeAdams, W. H. Heat Transmission McGraw-Hill Book Co., New York, USA (1954) 484 Handbook of Chemistry and Physics 58th Edn (Ed. R. C. Weast) CRC Press Inc., Florida, USA (1977) D-158, F-5-F-6, E-11, F-49F-51 JSME Steam Tablds The Japanese Society of Mechanical Engineers, Tokyo, Japan (1968) 88, 90
Temperature monitor and alarm system for cold storage rooms E. M. Lauro, J. D. Wismer and C. L. Chu Horticultural Products Laboratory, Horticultural Research Institute of Ontario, Vineland Station, Ontario, LOR 2E0 Canada Received 14 July 1986; revised 18 November 1986
A system has been developed at the Horticultural Research Institute of Ontario to monitor temperatures in 30 controlled atmosphere and specialty storage research rooms. Temperatures are recorded every 30 rain using resistance temperature'detectors, a data acquisition unit and a microcomputer. A computer program has also been developed to compare measured temperatures to high/low set points and to activate a Telesponder alarm system. The Telesponder is capable of signalling a remote pager and providing a synthesized voice message through the telephone system to operational personnel.
(Keywortls:cold storage; alarmsystems;temperaturemonitors)
Syst me de monitorage de la temp6rature et d'alarme pour chambres froides Un systbne a btb mis au point d l'lnstitut de Recherches Horticoles de l'Ontario pour monitorer les tempbratures dans 30 chambres d'essai ~ atmosphbre contr~l~e et d'entreposage de produits sp~ciaux. Les temperatures sont enregistrbes toutes les derai-heures au moyen de dbtecteurs de tempbrature ~ rbsistance, d'un systbme d'acquisition des donnbes et d'un micro-ordinateur. Un programme d'ordinateur a btb mis au point ~galement pour comparer les tempbratures mesurbes fi des valeurs de consigne blevbes/basses et pour dbclencher un systbme d' alarrae Telesponder. Le Telesponder peut signaler un point d' enregistrement bloignb et fournir au personnel d'exbcution un message parlb synth~tisb par le r~seau tblbphonique.
(Mots cl~s: entreposagefrigorifique;syst~mesd'alarme; monitorage de la temperature)
The storage life of perishable produce such as fruits and vegetables can be extended by the proper use of refrigerated storage. One of the most important factors influencing storage is the precise control of temperature. If the temperature of the produce is held for very long below the highest freezing point, then the stored crop can be ruined ~. The other extreme would be where the produce is held at too high a temperature, allowing a rapid rate of deterioration 2. Hence it was important to develop an accurate temperature monitoring and alarm system. 0140-7007/87/020106--02503.00 © 1987 Butterworth & Co (Publishers) Ltd and IIR
106
Int. J. Refrig. 1987 Vol 10 March
Description of equipment Temperatures are sensed using 100 f~ platinum resistance temperature detectors (RTD) connected in a four wire system. The wires from the RTD sensors in each room are routed back to a central instrument control room for channel relay multiplexing together with data acquisition equipment (Hewlett Packard 3497A). A Hewlett Packard HP86 microcomputer is used to control the data acquisition unit through a BASIC program. This program reads the recorded voltages from
Short communications the RTDs and calculates the corresponding temperatures using an equation 3 of the form: RT = R o + Ro
t
'-
I°--I SET POINT
1
I°-.I ALARM STATUS
where: iNITIALIZE RECORDING SEQUENCE
RT = resistance at temperature T; Ro = resistance at T= 0°C; 0t = temperature coefficient at T=0°C (typically + 0 . 0 0 3 9 2 ~ D - 1°C); 6 = 1.49 (typical value of 0.00392 platinum); and fl = 0 for T> 0°C or 0.11 (typical) for T< 0°C.
The data is then stored on floppy disc, and a hard copy of the temperature data can be obtained using a graphics printer. The equipment used to indicate alarm situations includes a programmable Telesponder model E8S voice response alarm system that can access the telephone lines. The Telesponder has the capability to sound a local alarm and also call a telephone number to transmit a synthesized voice message. Description of software
A BASIC computer program has been developed with the following capabilities: 1. commands the data acquisition system to scan 30 sensors; 2. receives recorded voltages and converts them to corresponding room temperatures; 3. displays temperature data on the monitor and stores them on floppy disc; 4. compares recorded temperature with previously stored upper and lower temperature alarm limits; 5. allows easy access to change stored set points and upper/lower alarm temperatures; 6. accesses an external alarm system when the situation is warranted and prints room number, temperature and time; and 7. allows either current or recorded temperatures to be displayed on a monitor and printed. The program is menu driven and consists of a main control section that provides the options shown in Figure 1. System operation
The temperature monitoring system can be continuously operated and scans 30 RTDs every 30 rain. The computer calculates and displays the corresponding temperatures and compares them with stored desired values. If the room temperature is out of the desired range, a counter is
RECORD AND DISPLAY ROOM TEMPS,
Figure 1 Flow chart showing options from the main menu Figure 1 Schbma d'emploi montrant les options de programme ~ partir du menu principal
initiated to indicate that an alarm situation has occurred. The alarm temperature is printed along with the corresponding room number and time. If the counter reaches N = 3, indicating this alarm situation is persisting, then a normally closed switch in the data acquisition system is opened, thereby triggering one or more of the eight Telesponder alarm points. At the beginning of each day, a summary of the previous days temperature data is printed, as well as the average temperature for each room. At any time during the automatic recording sequence, a current temperature status for each room can be obtained. Also, temperature set points and alarm levels can be changed to suit current situations. Discussion
The system described in this Paper has been tested over a period of one storage season and has been found to be extremely accurate (_+ 0.1°C) and reliable. It also provides the flexibility required when dealing with several cold storage units 4. Automated systems that provide a continuous watch over stored produce can be of extreme value, especially when the success of research projects is at stake and where mistakes can prove to be very costly. References
1 Lutz, J. M., Hardenburg, R. E. The commercialstorage of fruits, vegetables, and florist and nursery stocks in USDA Aoricultural Handbook No. 66 (1977)2 4 2 Bartsch,J. A. Refrigerationand controlled atmosphere storage for horticultural crops, NRAES-22, Cornell University, Ithaca, New York, USA (1984) 3 Practicaltemperaturemeasurements,Hewlett Packard Application Note 209, Hewlett Packard, Oregon, USA (1980) 16-19 4 Lauro,E. M. Chu,C. L., Smith, R. ELResearchfacilities for improved storage of fruit and vegetablecrops Can Soc Aoric Eno (1985)Paper No. 85-414
Corrigenda Soumerai, H. Predicting heat pump performance by thermodynamic generalizations of fluid flow and heat transfer data lnt J Refrig (1986) 9 113-120 Page 113, Equation (1) should read: C O P c = 1/[1 - (TL/T.)]
0140-7007/87/020107-02503.00 © 1987 Butterworth & Co (Publishers)Ltd and IlR
Page 115, Equation (3a) should read: (APtp)aso2 = [(V")RSO2/(V")R22](APm)R22 Page 117, Equation (5), the term (v") should read (v") +. The author apologizes for these errors.
Rev. Int. Froid 1 987 Vol 10 Mars
107
#f, where this variation increases to 2 9,~.
References l
Parameters for function P
Temperature range (K)
Maximum deviation (%)
pf (kgm 3) cpf (kJ kg- 1 K - 1) kf (W m - t K - t ) /~f (× 10 -6 Pas) hfg (kJ kg- ~)
0-300 0-300 0-300 0-300 1-200
0.131 0.441 0.263 2.017 0.025
2 3 4 5
Eckert, E. R. G., Drake, R. M. Analysis of Heat and Mass Transfer McGraw-Hill Book Co., New York, USA (1972) 777 ASHRAE Handbook of Fundamentals ASHRAE, USA (1981) 6.96.11 MeAdams, W. H. Heat Transmission McGraw-Hill Book Co., New York, USA (1954) 484 Handbook of Chemistry and Physics 58th Edn (Ed. R. C. Weast) CRC Press Inc., Florida, USA (1977) D-158, F-5-F-6, E-11, F-49F-51 JSME Steam Tablds The Japanese Society of Mechanical Engineers, Tokyo, Japan (1968) 88, 90
Temperature monitor and alarm system for cold storage rooms E. M. Lauro, J. D. Wismer and C. L. Chu Horticultural Products Laboratory, Horticultural Research Institute of Ontario, Vineland Station, Ontario, LOR 2E0 Canada Received 14 July 1986; revised 18 November 1986
A system has been developed at the Horticultural Research Institute of Ontario to monitor temperatures in 30 controlled atmosphere and specialty storage research rooms. Temperatures are recorded every 30 rain using resistance temperature'detectors, a data acquisition unit and a microcomputer. A computer program has also been developed to compare measured temperatures to high/low set points and to activate a Telesponder alarm system. The Telesponder is capable of signalling a remote pager and providing a synthesized voice message through the telephone system to operational personnel.
(Keywortls:cold storage; alarmsystems;temperaturemonitors)
Syst me de monitorage de la temp6rature et d'alarme pour chambres froides Un systbne a btb mis au point d l'lnstitut de Recherches Horticoles de l'Ontario pour monitorer les tempbratures dans 30 chambres d'essai ~ atmosphbre contr~l~e et d'entreposage de produits sp~ciaux. Les temperatures sont enregistrbes toutes les derai-heures au moyen de dbtecteurs de tempbrature ~ rbsistance, d'un systbme d'acquisition des donnbes et d'un micro-ordinateur. Un programme d'ordinateur a btb mis au point ~galement pour comparer les tempbratures mesurbes fi des valeurs de consigne blevbes/basses et pour dbclencher un systbme d' alarrae Telesponder. Le Telesponder peut signaler un point d' enregistrement bloignb et fournir au personnel d'exbcution un message parlb synth~tisb par le r~seau tblbphonique.
(Mots cl~s: entreposagefrigorifique;syst~mesd'alarme; monitorage de la temperature)
The storage life of perishable produce such as fruits and vegetables can be extended by the proper use of refrigerated storage. One of the most important factors influencing storage is the precise control of temperature. If the temperature of the produce is held for very long below the highest freezing point, then the stored crop can be ruined ~. The other extreme would be where the produce is held at too high a temperature, allowing a rapid rate of deterioration 2. Hence it was important to develop an accurate temperature monitoring and alarm system. 0140-7007/87/020106--02503.00 © 1987 Butterworth & Co (Publishers) Ltd and IIR
106
Int. J. Refrig. 1987 Vol 10 March
Description of equipment Temperatures are sensed using 100 f~ platinum resistance temperature detectors (RTD) connected in a four wire system. The wires from the RTD sensors in each room are routed back to a central instrument control room for channel relay multiplexing together with data acquisition equipment (Hewlett Packard 3497A). A Hewlett Packard HP86 microcomputer is used to control the data acquisition unit through a BASIC program. This program reads the recorded voltages from
Short communications the RTDs and calculates the corresponding temperatures using an equation 3 of the form: RT = R o + Ro
t
'-
I°--I SET POINT
1
I°-.I ALARM STATUS
where: iNITIALIZE RECORDING SEQUENCE
RT = resistance at temperature T; Ro = resistance at T= 0°C; 0t = temperature coefficient at T=0°C (typically + 0 . 0 0 3 9 2 ~ D - 1°C); 6 = 1.49 (typical value of 0.00392 platinum); and fl = 0 for T> 0°C or 0.11 (typical) for T< 0°C.
The data is then stored on floppy disc, and a hard copy of the temperature data can be obtained using a graphics printer. The equipment used to indicate alarm situations includes a programmable Telesponder model E8S voice response alarm system that can access the telephone lines. The Telesponder has the capability to sound a local alarm and also call a telephone number to transmit a synthesized voice message. Description of software
A BASIC computer program has been developed with the following capabilities: 1. commands the data acquisition system to scan 30 sensors; 2. receives recorded voltages and converts them to corresponding room temperatures; 3. displays temperature data on the monitor and stores them on floppy disc; 4. compares recorded temperature with previously stored upper and lower temperature alarm limits; 5. allows easy access to change stored set points and upper/lower alarm temperatures; 6. accesses an external alarm system when the situation is warranted and prints room number, temperature and time; and 7. allows either current or recorded temperatures to be displayed on a monitor and printed. The program is menu driven and consists of a main control section that provides the options shown in Figure 1. System operation
The temperature monitoring system can be continuously operated and scans 30 RTDs every 30 rain. The computer calculates and displays the corresponding temperatures and compares them with stored desired values. If the room temperature is out of the desired range, a counter is
RECORD AND DISPLAY ROOM TEMPS,
Figure 1 Flow chart showing options from the main menu Figure 1 Schbma d'emploi montrant les options de programme ~ partir du menu principal
initiated to indicate that an alarm situation has occurred. The alarm temperature is printed along with the corresponding room number and time. If the counter reaches N = 3, indicating this alarm situation is persisting, then a normally closed switch in the data acquisition system is opened, thereby triggering one or more of the eight Telesponder alarm points. At the beginning of each day, a summary of the previous days temperature data is printed, as well as the average temperature for each room. At any time during the automatic recording sequence, a current temperature status for each room can be obtained. Also, temperature set points and alarm levels can be changed to suit current situations. Discussion
The system described in this Paper has been tested over a period of one storage season and has been found to be extremely accurate (_+ 0.1°C) and reliable. It also provides the flexibility required when dealing with several cold storage units 4. Automated systems that provide a continuous watch over stored produce can be of extreme value, especially when the success of research projects is at stake and where mistakes can prove to be very costly. References
1 Lutz, J. M., Hardenburg, R. E. The commercialstorage of fruits, vegetables, and florist and nursery stocks in USDA Aoricultural Handbook No. 66 (1977)2 4 2 Bartsch,J. A. Refrigerationand controlled atmosphere storage for horticultural crops, NRAES-22, Cornell University, Ithaca, New York, USA (1984) 3 Practicaltemperaturemeasurements,Hewlett Packard Application Note 209, Hewlett Packard, Oregon, USA (1980) 16-19 4 Lauro,E. M. Chu,C. L., Smith, R. ELResearchfacilities for improved storage of fruit and vegetablecrops Can Soc Aoric Eno (1985)Paper No. 85-414
Corrigenda Soumerai, H. Predicting heat pump performance by thermodynamic generalizations of fluid flow and heat transfer data lnt J Refrig (1986) 9 113-120 Page 113, Equation (1) should read: C O P c = 1/[1 - (TL/T.)]
0140-7007/87/020107-02503.00 © 1987 Butterworth & Co (Publishers)Ltd and IlR
Page 115, Equation (3a) should read: (APtp)aso2 = [(V")RSO2/(V")R22](APm)R22 Page 117, Equation (5), the term (v") should read (v") +. The author apologizes for these errors.
Rev. Int. Froid 1 987 Vol 10 Mars
107