Fukui, T

Kodera, M

Kumagai, K

Masuda, T

Shimada, T

Tanaka, R

Yamashita, A

CERN Document Server

HIGH PRECISION TEMPERATURE MEASUREMENT SYSTEM USINGSMARTLINK AT SPRING-8T. Fukui, M. Kodera, K. Kumagai, T. Shimada, T. Masuda, R. Tanaka and A. Yamashita, SPring-8, Hyogo, JapanAbstractWe developed a high precision temperaturemeasurement system using SmartLink within the SPring-8 standard control framework. In the storage ring ofSPring-8, a stable magnet’s temperature is essential tokeep the beam orbit stable. The precise measurement ofthe magnet cooling water temperature with a resolution of0.01˚C is a requested goal because 0.1˚C temperaturedeviation causes a few micron beam position distortions.The SmartLink is a general-purpose measuring instrumentdesigned for network-based system. Its resolution isguaranteed 0.01˚C for thermocouples and 0.001˚C forresistive temperature detectors respectively. The systemcan be installed to any place along with the storage ringwith the limited space. The temperature data from theSmartLink is taken by socket based networkcommunication with a UNIX workstation and stored intothe accelerator database system. In this article, temperaturemeasurement system and results are presented.1  INTRODUCTIONWe developed a high precision temperature measurementsystem using SmartLink1 within the SPring-8 standardcontrol framework[1]. The compact form factor ofSmartLink, as shown in figure 1, makes it easy to putthem close to the signals or sensors being monitored.Figure 1: View of SmartLink.The poller and collector data-taking processes arerunning on the UNIX workstation. The poller processtakes the data from the SmartLink by using a socket basednetwork communication with bootp client protocol, andstores the data into a shared memory. The collector                                                1 SmartLink is a trademark of Keithley Instruments Inc..process reads the data from the shared memory and storesthe data into the accelerator database system. We use typeT thermocouples (TC’s) to measure the magnet coolingwater temperature and platinum resistive temperaturedetectors (RTD’s) with 4 wire configuration to measurethe underground temperature.  The intervals of data takingare 10sec for the cooling water temperature and 60sec forthe underground temperature.In storage ring of the SPring-8, the cooling watersystems consist in four zones. We measure thetemperature of the water supplied to magnets, theoutgoing water from magnets, and the air temperature ofeach zone. Even 0.1˚C temperature deviation of thecooling water causes a few micron beam positiondistortions[2]. So it is essential to request the precisemeasurement of the magnet cooling water temperaturewith 0.01˚C accuracy.For the measurement of underground temperature, weinstalled the SmartLink with RTD’s into the wave-guidepit for the RF cavities. Each RTD is set into the level of3.6m below the storage ring medium plane ( 2.4m belowthe base plate ) and 3m depth from sidewall of the pit.The SmartLink is covered by lead blocks to avoidradiation damage. Also we install the RTDs to measurethe underground temperature around the storage ring withthe depth of 0m, 0.5m, 3m, 5m and 10m below thesurface.Figure 2: Schematic view of SmartLink testbench.10base-T HUBHP9000/C110with HP-UX 10.20TCs or RTDsSmartLinkMAUMAUInternational Conference on Accelerator and Large Experimental Physics Control Systems90International Conference  Accel rator and L rge Experim ntal Physics Control Systems, 1999, Trieste, Italy2  PERFORMANCE ON THE TESTBENCH2.1  SetupOn the testbench we use two SmartLinks and oneUNIX workstation. In order to reduce the measurementsystematic errors, the TC and the RTD are connected toboth SmartLinks at the same time, and all sensors readthe same temperature. The SmartLinks are connected tothe workstation via 10base-T Ethernet. The poller processis running on the UNIX workstation to take the data.Figure 2 shows schematic view of SmartLink testbench.Figure 3: Difference of two RTD’s.2.2  Test ResultsThe SmartLink has the function of internal averagingup to 50 times. The data acquisition time and accuracywere measured for 1, 4, 10 and 50 averaging modes. Table1 and 2 show the data acquisition time of each reading.This measurement includes the processing time a tSmartLink, the propagation delay of networkcommunication and the poller process time. The dataacquisition time is almost proportional to the number ofinternal averaging and no difference is found between theTC and the RTD. A maximum value of the dataacquisition time with no averaging is almost twice theaverage data acquisition time and we did not know thereason at this moment.Figure 3 shows the distribution of the differencebetween the two RTD’s with no averaging. The standarddeviation is 0.0083˚C.For estimation of accuracy we assume as follows:• Τhe error distribution is Gaussian distribution.• Both SmartLink have the same accuracy.• There is no correlation between two SmartLinks.The relative accuracy σSmartLink is given as,It meansTable 1: Data acquisition time of TCInt.A v e .Average Minimum Maximum1 118msec 109msec 229msec4 372msec 368msec 385msec10 965msec 925msec 997msec50 4.75sec 4.70sec 4.79secTable 2: Data acquisition time of RTDInt.A v e .Average Minimum Maximum1 109msec 104msec 168msec4 378msec 376msec 394msec10 825msec 795msec 876msec50 4.02sec 3.95sec 4.49secTable 3 shows the accuracy of TC and RTD with1,4,10 and 50 averaging.Table 3: Relative accuracy of TC and RTDAverage with TC with RTD1 0.0139 0.00594 0.0119 0.003810 0.0123 0.003950 0.0248 0.0022The accuracy of RTD is proportional to the square rootof averaging are up to 4 times. This means that the errorsdescribed as normal error distribution and systematic errorsare dominating below 0.004˚C. On the other hand, theaccuracy of TC is not proportional to the square root ofaveraging because the accuracy has reached the sensorresolution ( 0.01˚C ).3  PERFORMANCE WITH STORAGERINGWe started to measure the cooling water temperatureand the underground temperature from the beginning of1999. For the first few months, the data acquisition wasunstable. The SmartLinks were hung-up every severalhours. This was caused by the minor bugs of the networkprotocol stack of the SmartLink’s firmware. However, theSmartLink with the new version of the firmware isrelatively stable. Troubles like system hung-up have beenrecorded about three times in 5 months.0100200300400500600-0.016-0.010-0.0040.0020.0080.0140.0200.0270.0330.0390.045DifferenceCountsσ σ σDifference SmartLink SmartLink2 2 2= + .σσSmartLinkDifference=2.91Figure 4: Difference of two TC’s.Figure 4 shows the supply and outgoing cooling watertemperature with no averaging. A temperature of supplywater is controlled within ±0.2˚C and a time constant isabout 10 to 20 minutes. A hunching of cooling water is acharacter of the temperature control system and it will beimproved in future. The difference between thetemperature of the supplied and outgoing cooling water iscaused by the heat load of pump system.05001000150020002500-0.046-0.036-0.026-0.017-0.0070.0030.0130.0230.0320.042DifferenceCountsNo AvgAvg 10Figure 5: Difference of no average and 10 times averagingof RTDs.If the heat load is constant, a difference between thesupply and the outgoing cooling water temperature isconstant. We selected as stable a condition as possible.The main magnets of the storage ring were not operated inthis period, the heat load was negligibly small. Thestandard deviation of the difference was 0.0222˚C andrelative accuracy was 0.017˚C. This is close to therequested value of 0.01˚C accuracy.For the underground temperature measurement we usethe two RTDs for each position. Figure 5 shows thedifference between two RTDs with no averaging and 10times averaging. The 10 times averaging is narrower thanthe no averaging.Table 4: Relative accuracy of RTDσNo Average 0.010310 times average 0.003510 times average after 5 month 0.0032Table 4 shows the accuracy of no average, 10 timesaveraging and again 10 times averaging but 5 month.After 5 month the relative accuracy has not degraded.4  SUMMARY AND CONCLUSIONWe developed a high precision temperaturemeasurement system using SmartLink within the SPring-8 standard control framework. The system has beenoperating for more than 5 months and performs very wellthe precise measurement of the magnet cooling watertemperature and the underground temperature. On thetestbench, the relative accuracy of TC is about 0.01˚C andthe relative accuracy of RTD is less than 0.01˚C. The dataacquisition time is about 100msec for no averaging andabout 1sec for 10times averaging. This is good enoughfor the data taking intervals of 10 sec for the coolingwater and 60sec for underground temperature.At the storage ring environment, the relative accuracyof the system with TC is 0.016˚C. This is almost thesame accuracy of the testbench and close to requested goal.The relative accuracy of the system with RTDs is0.0103˚C with no averaging and 0.0032˚C with 10 timesaveraging. When compared to the testbench results, theaccuracy is degraded. This is caused by the distance of the3m extension from the RTD to the SmartLink. Theaccuracy of SmartLink is good enough for themeasurement of the magnet cooling water andunderground temperature.REFERENCES[1] R.Tanaka et al., Proc. of ICALEPCS’95, Chicago,USA, 1995, p.201.[2] K. Kumagai et al., ”Beam Orbit Distortion caused byTemperature Fluctuation of Cooling Water at SPring-8 Storage Ring”, The 12th Sympo. on Accel. Sci.and Tech., Wako, Japan, 1999.(to be published)29.5529.629.6529.729.7529.829.8529.929.95300:000:431:272:112:553:394:235:065:506:347:188:028:46Tim eTemperature( degree )inout92

High Precision Temperature Measurement System Using Smartlink at SPring-8

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