WORK PROJECT REPORT: PELTIER

ELEMENTS

CERN Summerstudent Programme 2015

Student: Laurits Tani < laurits.tani@gmail.com & laurits.tani@cern.ch >

Supervisors: Piero Gieorgio Verdini < Piero.Giorgio.Verdini@cern.ch >

Andromachi Tsirou < Andromachi.Tsirou@cern.ch >

Division: CMS, Tracker

Project Name: Peltier elements

Contents INTRODUCTION: ...................................................................................................................................... 1

CERN and CMS ..................................................................................................................................... 1

CMS and Peltier elements ................................................................................................................... 1

My work with Peltier elements ............................................................................................................... 1

Testing Peltier elements ...................................................................................................................... 2

Controlling Peltier elements ................................................................................................................ 2

Reading the data ................................................................................................................................. 3

Different Peltiers ................................................................................................................................. 5

Results and conclusion ............................................................................................................................ 5

Acknowledgements ................................................................................................................................. 6

APPENDIX ................................................................................................................................................ 7

MANUAL .............................................................................................................................................. 7

1

INTRODUCTION: My name is Laurits Tani and I’m a student of Engeneering Physics in Technical University Tallinn in Estonia. I got selected to Summer Student Programme 2015 and worked under the supervision of Piero Giorgio Verdini and Andromachi Tsirou. Next up I will introduce my project, what I did and the final results.

CERN and CMS The main fuction of CERN (The European Organization for Nuclear Research) is to provide particle accelerators and the main field of study at the moment is high energy physics. The biggest accelerator of CERN is LHC (Large Hadron Collider) that will ramp up to energy as high as 13 TeV this year. There are 4 main detectors at the LHC : ATLAS, CMS, ALICE and LHCb. Besides those there are also smaller detectors. ATLAS and CMS are general purpose detectors. Since I’m involved with CMS project, I will give a little introduction about CMS and how my project is related to it.

CMS and Peltier elements The CMS detector consists of the interaction point, tracker, calorimeter, hadronic calorimeter, magnet and muon chambres. My team worked with the tracker. The mission was to detect humidity near tracker, since inside and in the close periphery of the tracker where the services enter temperatures are very low and humidity can cause much harm to nearby electronics when it freezes. The quantity that has to be monitored in order to know if there is water or frost danger is the dewpoint, defined as is the temperature to which the air must be cooled to reach saturation (assuming air pressure remains the same). When the temperature cools to the dew point, fog or dew can occur, and the relative humidity becomes 100%. Indigenus idea was to place mirrors and use lasers to measure the humidity. Since this would have taken too much space, then the group started experimenting in order to build a simplified version of wet mirror working in a preventive mode. The simplified wet mirror will make use of Peltier elements for cooling and heating so there have been many studies for finding the correct Peltier. Peltier element is thermoelectic, that gains voltage when temperature difference between cold and hot side is made or changes temperature when voltage is applied. Pelter element has two sides: hot and cold side. The temperature difference between those sides will cause increased voltage.

My work with Peltier elements To control Peltier elements, temperature controller was used. I used TEC-1091 that was

manufactured my Meerstetter Engineering. To gain control with the temperature controller,

software had to be intalled on a controlling PC. There were different modes to control the Peltier:

Tempererature controller to control temperature, Static current/voltage to control voltage and

current and LIVE ON/OFF to auto-tune the controller respectively to the system. Also, since near the

collision pipe there is much radiation, radiation-proof Peltier elements have to be used. To gain the

best results, I had to find the most efficient Peltier elements and try to get their cold side to -40

degrees Celsius.

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Testing Peltier elements Peltier elements were tested in similar enviroment as it would be in CMS tracker (at temperature -30

degrees Celsius). To get this temperature, Peltier elements were placed in a freezer with controllable

temperature. In the cooling chamber were pipes, that were also set at temperature of -30 degrees of

Celsius. Peltier element was placed on the pipes with the hot side down, so the hot side would reach

the temperature of -30 degrees of Celsius.

To gain better heat exchange between the pipes and Peltier element the Peltier was placed

between two metal plates and the metal plates were tightened together. The thickness of the metal

plate in total (two sides) should be 16mm, since the thickness of the pipe in the middle is 10mm and

3mm will be on both sides over the pipe. There will be two kind of metal boxes, both of them have

the same thickness. One metal plate is 10mm x 10mm and the other is 25 mm x 25 mm. One metal

box consists of two metal plates.

As previously mentioned the mission was to reach -40 degrees of Celsius on the cold side. To

measure the temperature, several sensors were placed inside the freezer and on the cold and hot

side of the Peltier element. In the following the temperature of the hot side will be called sink

temperature and the temperature on the cold side will be called object temperature. The data of

object temperature and sink temperature was fed to the controller that changed the input voltage

and current respectively.

If cooling chamber was turned on, dry air was blowed inside the chamber to avoid condensation.

Controlling Peltier elements To begin with, to gain control over Peltier element it is supposed to be connected to the controlling

system. To do that I plugged all the wires in necessary places, USB cable included. When the

temperature controller (TEC-1091) was powered up and connected to the PC via USB cable, it started

installing required drivers for the TEC. Also software for the TEC was needed, whitch could be found

in the Internet. When all wires are connected correctly, the box in the bottom left corner of the

programme window should be green.

When I used the programme first time, I had to import the default configuration. Depending on what

temperature sensor (NTC/PT100/PT1000) I used, I chose from the „Expert“ tab the needed sensor.

The data from the sensors and the data input can be seen in Tab no. 1 named „Monitor“.

After a big change in the given orders in the sofware or in case of error, resetting TEC is needed in

order to control Peltier.

There are three sources that can control a channel's output stage: 'Static Current/Voltage' makes the

channel behave like a DC power-supply (with set current and voltage, temperature-independent).

Values are read from non-volatile memory. If 'Live Current/Voltage' is selected, current and voltage

values are taken from the device's volatile memory ('RAM') which can be continuously updated by

remote-control. In the 'Temperature Controller' mode the output current for cooling/heating is

calculated by the on-board firmware as a function of temperature and other information.

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Connecting Peltier wires correctly is essential because otherwise Peltier won’t behave as wanted. To

differ the cold and hot side, there is a tip: wires that are connected to Peltier are closer to the hot

side. It is essential to place the cold side upward. When data is changed in the TEC programme,

configuration should be saved or the software won’t use the written data.

There are many safety measures. For example voltage and current limits are intalled. In case of short

circuit or other problem where current and voltage will rise too high, error will occur and control

over TEC is lost.

The suggested PID values are starting values that proved to work reasonably well at factory. At a later

stage, they need to be optimized for a given application and system This will grant maximum

accuracy of the measurments. Since my thermal model was slow „Slow model“ and „Slow PI values“

were used. During Auto tune the system tries to optimize the system and seeks optimum PID values.

After auto tuning, write the data to TEC.

Eventhough there was a sensor measuring the sink temperature, this data doesn’t have to be used

since I could choose if the data is „external“ (coming from the sensor) or if it is „fixed value“

(temperature must be written manually).

Regarding sensors in case of NTC sensor, the data from the datasheet had to be used since every NTC

sensor is different. The same doesn’t apply to PT sensors since all PT100 are the same and all PT1000

have the same characteristics.

Also very important is to write the right data into the „Temperature measurment“ tab under the

„Expert“ tab. Often changing the settings in „CH1 Object Measurement Settings“ is forgotten and this

will consume alot of time to figure out what is wrong. With the PT sensors I used, PGA Gain was set

to „2“ ; current source was „500 μA“; ADC Rs was set to „3600 Ω“; ADC Calibration Offset was

„1138.9832“; ADC Calibration Gain was „0.9998794“ and sensor type was depending on what sensor I

used.

Furthermore if right sink temperature is wanted (external source is chosen), then CH1 Sink Measurment

Settings have to be changed accordingly to the sensor used to measure the sink temperature. In my case

the settings were: ADC Rv „5600 Ω“; ADC Vps „3.3 V“; ADC calibration offset „-12.2382“ ; ADC Calibration

Gain „1.010536“.

Since we used only one channel, then only data to the CH1 boxes were filled because CH2 data was

not used.

Reading the data Data can be read in the „Monitor tab“ or „Chart tab“ . Chart tab is very useful when wanting to see

previous data – on the first chart there will be displayed the changes in temperature on the Y-axis

and time on the X-axis. The size of the chart can be changed respectfully to what is more convenient

or practical.

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On the second chart current in Amperes will be showed on Y-axis and time on X-axis. The first and

second chart will have time axis in correspondence to each other – that means that you can see how

the temperature is depending on the current and vice versa.

As previously mentioned then the data fed by the sensors can be observed also in „Monitor“ tab. The

data given there will be only the data in real time and it won’t show previous records. This excluded,

„Monitor“ tab is better to observe the data on the Peltier since other data will be displayed in that

tab too.

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When finished testing or controlling the Peltier, the data can be exported from „Maintenence“ tab.

The exported data will be saved in CSV format. This can be opened with various programmes (e.g MS

Excel, Notepad etc.) although if in need to analyse the data, then MS Excel or programme similar to

this would be advised.

Different Peltiers Under testing were different kind of Peltiers – the conventional ones that can be purchased

everywhere and radiation-tolerant Peltier elements, that are filled with special gue that is radiation-

resistant. Both had to be tested in order to obtain information about their efficiency. Conventional

Peltier elements will be tested with a special radiation-tolerant gue and the efficiency will once again

be measured.

Results and conclusion Regarding this project, gaining control over Peltier elements was successful. We managed to reach

the temperature of -40 degrees of Celsius on the cold side with the required Peltier elements when

the temperature of the enviroment was -30 degrees of Celsius.

All this work led me to write the manual for TEC-1091 for the use of everybody who wants to test

Peltier elements in the cooling facility.

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For me personally, the experience gained during my summer internship lies mostly in hardware

handling when setting up the measurments for Peltier elements.

Acknowledgements Andromachi Tsirou - supervisor

Piero Giorgio Verdini - supervisor

Sale-Iti Kroon – fellow summer student with the same project

Imitaz Ahmed – technician

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APPENDIX

MANUAL

TEC-1091 Manual

1. Preparing TEC, connecting the wires

VIN wire is the “ +“ wire of the power source (we have 24V power source) and this is usually white or

red.

GND wire is the grounding wire of the power source (24V) and this is usually black

OBJ T° IA is the object temperature sensor’s black wire

OBJ T° IB is the object temperature sensor’s green wire

OBJ T° UA is the red wire of the object’s temperature sensor

OBJ T° UB is the white wire of the object’s temperature sensor

SINK T° A is the wire from sink temperature sensor (does not matter whitch wire)

SINK T° B is the wire from sink temperature sensor (does not matter whitch wire)

OUT - is the „-’’ wire of the Peltier element

OUT + is the „+’’ wire of the Peltier element

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SHIELD plug will be left empty

RES1 plug will be left empty

RES2 plug will be left empty

RES3 plug will be left empty

RES4 plug will be left empty

RS232 RX plug will be left empty

RS232 TX plug will be left empty

RS485 A2 plug will be left empty

RS485 B2 plug will be left empty

X3 is the mini USB port

2. Pay attention to what way you put Peltier element. Usually the hot side is down [hot side is

the side where the wires are closer] More about hot and cold side later.

3. If everything is connected, you are ready to plug the USB cable to the computer. (TEC does

not have to be powered up). In case of plugging TEC first time to the computer, the computer

will install the drivers (this will be done automatically). If Windows fails to install drivers, then

they are available on the following webpage:

http://www.ftdichip.com/Drivers/CDM/CDM%20v2.10.00%20WHQL%20Certified.exe\

4. If you do not have the necessary software of the TEC in the computer, you can download

them from the manufacturer’s (Meerstetter Engineering) website:

http://www.meerstetter.ch/products/tec-controllers/tec-1091

5. Download the file under the name „TEC-Family TEC Controllers Software Package“ . If you

downloaded the software, you got .zip file. You need to extract it.

6. In case every piece of software is installed, you are ready to run the programme (the name of

the programme is „TEC Service...“

7. When using this programme first time you need to import the default configuration clicking

„Import config“ in the bottom of the programme window

8. The default configuration file is in the same folder as the programme launcher.

9. TEC service software displays: “No compatible device free” because the TEC controller is not

yet powered

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10. Plug in the power cable. The device status should show ready and the left box should be

green as shown on the picture below:

11. Before running the programme, right data have to be inserted and right commands have to

be given. Since we are running with only one channel then only CH1 fields have to be filled

in

12. Log into the programme as „expert“ and a new tab will appear called „Expert“. There choose

the right sensors. In case PT100 or PT1000 new data about them does not have to be written,

since all PT100 are similar and the same applies to PT1000 (TEC will use internally stored

settings for PT100 and PT1000). In case of NTC sensor, required fields have to be filled in

(more info will follow) . To increase accuracy use 4 wire PT100 or PT1000.

13. Be sure to fill in right data to „Expert“ tab. An example picture is given below:

14. Object temperature (tab5) In order to read right data, correct input data has to be written. If

NTC sensor is used, CH1 Object NTC sensor Characteristics have to be filled in from the

datasheet. If you use PT100 or PT1000 for measuring object temperature then these fields

don’t have to be filled in. CH1 Actual Object Temperature Error Limits should be filled in

depending on what temperature is needed to reach.

Temperature stability criteria are user-defined and consist of a temperature range and a time

frame. They are entered into 'CH1 Object Temperature Stability Indicator Settings' in Tab

'Object Temperature' (2x ‘Temperature Deviation’. For actual object temperature judged to

be stable, it must have been within 'Temperature Window' of target object temperature for

'Min Time in Windows' or more. This means that if actual object temperature falls out of

'Temperature Window', stability indication is immediately lost (and will return the earliest

after the delay of 'Min Time in Windows').

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15. SINK TEMPERATURE: Same applies to Sink temperature tab as it did to Object Temperature.

Nonetheless there is a slight difference – CH1 Sink Temperature Source Selection. There can

be chosen Fixed Value or External . If no Sink Temperature sensor is connected, then it is

advised to choose Fixed value and write the sink temperature manually otherwise the

programme will give wrong data. Choose „External“ if there is a sensor connected and it will

give accurate data live. Sink NTC Sensor Characteristics are always relevant (i.e. they cannot

be superseded by Pt100/Pt1000 internal data).

16. Operation: In CH1 Output Stage Control Input Selection mode for the TEC has to be chosen.

Since we are trying to control the temperature of Peltier, Temperature Controller has to be

clicked. In case of needing to control voltage and current Statin Current/voltage is the right

choice. To enable TEC to control Peltier CH1 Output Stage Enable has to be STATIC ON. When

not using TEC, be sure to turn STATIC OFF. Live ON/OFF is the right choice when Auto tune is

wanted to be done. (More about Auto Tuning later in manual). CH1 Outuput Stage ’Static

Current/Voltage’ Control Values has to be filled in only in case „Static Current/voltage“ is

chosen. Data depends on task and data of hardware (Peltier). CH1 Output Stage Limits data

depends also on the characteristics of given Peltier element (Error thresholds should be

within 20% over the corresponding limit). Usually voltage limitation is 1V over Umax of the

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Peltier. Attribute a unique 'Device Address' if you are operating multiple TEC controllers.

Also be sure to choose from General Operating Mode “Single (Independent)”

17. Temperature Control: To reach the desired object temperature Target Object Temp has to

be filled in. Coarse Temp Ramp and Proximity Width are characteristics that change the

speed of temperature change. In CH1 Modelization for Thermal Power Regulation Full

control has to be chosen in order to control Peltier fully (so the controller can heat and cool

the object using the Peltier element). Also Peltier Characteristics have to be filled in in

Temperature Control tab since Peltiers are different and therefore also act different at given

voltage/current/temperature since they have different characteristics. CH1 Resistor

Characteristics have to be filled in only in case of usage of a resistor. These characteristics

cannot be used to limit the output (Limits are set in tab 3). For driving an ohmic heater

('Resistor, Heat Only' mode), enter its resistance and maximal current in the fields provided.

18. Auto Tuning: Auto tuning is advised to use after every new Peltier since they all have

different characteristics and will act differently. Using auto tune results reaching the desired

temperature with lesser fluctuation is faster. To run Auto Tune Live ON/OFF has to be

chosen from Operation tab. Be sure to use Slow model and to use Slow PI values in order to

increase accuracy.

Before tuning, it is recommended to export the current device configuration, or to note the

current 'CH1 Temperature Controller PID Values' (Tab 'Temperature Control') as well as the

ramping/proximity parameters from 'CH1 Nominal Temperature'.

19. Monitor and Chart: Data can be read in the „Monitor tab“ or „Chart tab“ . Chart tab is very

useful when wanting to see previous data – on the first chart there will be displayed the

changes in temperature on the Y-axis and time on the X-axis. The size of the chart can be

changed respectfully to what is more convenient or practical.

As previously mentioned then the data fed by the sensors can be observed also in „Monitor“

tab. The data given there will be only the data in real time and it won’t show previous

records. This excluded, „Monitor“ tab is better to observe the data on the Peltier since other

data will be displayed in that tab too.

If the Peltier is changing it is temperature the wrong way, then it is connected backwards.

20. Maintenance: When finished testing or controlling the Peltier, the data can be exported

from „Maintenance“ tab. The exported data will be saved in CSV format. This can be opened

with various programmes (e.g. MS Excel, Notepad etc.) although if in need to analyse the

data, then MS Excel or programme similar to this would be advised.

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21. To save the data inserted, press “Write config”

22. Run the programme and turn STATIC ON

23. Information about your TEC Controller is displayed on the top right corner of the first tab.

24. If an error occurs, the description is displayed in the monitoring tab.

Pictures

(On the picture: Metal box that was fastened to the cold pipe and what was connected to Peltier)