DX4090 Manual

Z-метр DX4090
User Guide
Version 1.03
RMT Ltd
Moscow, 2015
Z-Meter DX4090
RMT Ltd
CONTENTS
1. INTRODUCTION ........................................................................................................................... 3
1.1. Objectives ................................................................................................................................ 3
1.2. System Requirements .............................................................................................................. 4
2. TECHNICAL CHARACTERISTICS ................................................................................................ 4
2.1. Z-Meter Specifications ............................................................................................................. 4
2.2. Other Features ........................................................................................................................ 4
2.3. Standard Delivery Kit ............................................................................................................... 5
3. DESCRIPTION .............................................................................................................................. 6
3.1. Design overview. ...................................................................................................................... 6
4. WORKING WITH Z-METER .......................................................................................................... 7
4.1. External connections. ............................................................................................................... 7
4.2. USB Drivers Installation ........................................................................................................... 7
4.3. Software Installation ................................................................................................................. 8
5. MEASUREMENT OF TE MODULES PARAMETERS .................................................................... 9
5.1. TE Modules Connection ........................................................................................................... 9
5.1.1. Measurements of TECs in internal chamber. ...................................................................... 9
5.1.2. External TEC measurements ............................................................................................. 9
5.2. Working with Program ............................................................................................................ 10
5.3. Program Main Window ........................................................................................................... 10
5.3.1. Menu Bar ......................................................................................................................... 11
5.3.2. Reference Bar .................................................................................................................. 11
5.3.3. Functional Fields .............................................................................................................. 12
5.4. Measurements of R, Z,  ........................................................................................................ 13
5.4.1. Temperature Setting......................................................................................................... 13
5.4.2. TE Module Type ............................................................................................................... 13
5.4.3. Corrections Field .............................................................................................................. 14
5.4.4. Parameters for Header Thermal Resistance .................................................................... 14
5.5. Measurement Procedure and Notes....................................................................................... 15
5.6. History 17
5.6.1. File ................................................................................................................................... 17
5.6.2. Options............................................................................................................................. 18
5.6.3. Report .............................................................................................................................. 18
5.7. TE Modules Database Update ............................................................................................... 19
6. TEC DYNAMICS PROCESSING ................................................................................................. 21
6.1. Time Constant Measuring ...................................................................................................... 21
6.2. Interpolation Results .............................................................................................................. 21
7. FIGURE-OF-MERIT Z MEASURING ........................................................................................... 22
7.1. Single-stage TE Module Z ...................................................................................................... 22
7.2. Two-stage TE Module Z ......................................................................................................... 24
7.3. Alternative Correction............................................................................................................. 25
8. MEASURING PROCESSES ........................................................................................................ 25
8.1. AC Resistance Measurement................................................................................................. 25
8.2. Measurement of U and Uα Telemetry ..................................................................................... 26
8.3. Voltages Measurement for Testing Z ..................................................................................... 27
8.4. Checking of TE Module Polarity ............................................................................................. 27
9. MAINTENANCE.......................................................................................................................... 28
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Z-Meter DX4090
1. INTRODUCTION
1.1. Objectives
The Z-Meter provides measurement of following parameters of thermoelectric (TE) modules (also TE
coolers, TECs):
 AC Resistance (R),
 Figure-of-Merit (Z),
 Time Constant ().

Maximum Temperature Difference* (Tmax)
* For thermoelectric coolers (TECs) the measured Figure-of-Merit allow to calculate additional
performance parameter - maximum temperature difference Tmax. The calculation is valid for singlestage TECs. Measured Z for multistage TECs correlates with the cooling capacity, but no possibility for
simple calculation of it.
The parameters are measured at the ambient temperature. The software provides recalculation of TEC
resistance and maximum temperature difference to other ambient temperatures if required.
The Z-Meter allows testing of various types of single- and two-stage TE modules and submounts with a
single-stage coolers. It also allows evaluation of quality of more-stage TE modules by measurement of
their AC resistance.
The Z-Meter is operated by computer under the operating system MS Windows: 98/2000/XP/Vista/7 or
higher.
ADVANTAGES


Express testing performance of
single
stage
and
multi-stage
thermoelectric modules
Testing performance of TE modules
integrated into optoelectronic devices
(photodetectors, lasers etc.)

Time constant measurement

Compatible with other Z-Meters of
RMT’s Devices Family.
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FEATURES

Portable design

Current adjustable in a range 0...80 mA

Measurement at direct and reversed
current

Results normalization to standard
temperatures

Correction coefficients to Z value

Low power consumption
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1.2. System Requirements
Any Z-Meter requires connection to a PC and installation of “Z-meter” software. The software is
delivered along with Z-Meters or may be downloaded from www.rmtltd.ru. The interface is simple and
does not require User's special knowledge ore experience.
General system requirements are as follows:
 Free USB port,
 20 MB free hard drive space (additional space may be required later to store database for
various types of coolers),
 Mouse or compatible pointing device.
2. TECHNICAL CHARACTERISTICS
2.1. Z-Meter Specifications
Parameters
Units
Values
Electrical resistance
Range
Ohm
0.1...100
Accuracy
%
0.6 (but>0.01Ohm)
Repeatability
%
0.3
Figure-of-Merit Z
Range
10-3/K
1...4
Accuracy
%
1.5
Repeatability
%
0.4
Time Constant
Range
s
1...100
Accuracy
%
1.5
Repeatability
%
1
Power Supply
Voltage
V
5 (USB connector)
Current
mA
250
Operational Conditions
Ambient
temperature
°C
15...35
range
Relative humidity
%
0...95
Mechanical Parameters
Dimensions
mm
160х66х30
Weight
kg
0.24
°C
Storage
temperatures
-20…+60
range
%
Humidity
5…95%
2.2. Other Features
-
The Z-meter has an internal chamber for placing a TEC under measurements. It is always
recommended to place TECs into this chamber. If TEC size does not fit the chamber, such a
TEC may be placed outside and connected to Z-meter by external cable enclosed. In both
cases, four-wire connections are used to ensure the most precise measurements. Note free air
convection around the TEC is required in case of measurements of TECs outside the internal
chamber..
-
The Z-meter allows checking of TEC polarity simultaneously with TEC parameters
measurement.
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Z-Meter DX4090
2.3. Standard Delivery Kit
Z-meter DX4090
1 pcs.
Cable with 4-wire terminals for external
testing *
1 pcs.
Cable USB AM / miniUSB-B
1 pcs.
CD or USB Flash (Software, Manual)
* Measuring terminals can be made on the basis of Kelvin klips of various designs.
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3. DESCRIPTION
3.1. Design overview.
The Z-meter is a single-unit device with internal chamber for TECs. Chamber’s cover is magnetically
locked when closed or opened.
The internal chamber is a passive thermostat which provides constant TEC temperature during
measurements. Terminals inside allow easy connection of measured TEC. Temperature inside the
chamber is measured by an appropriate thermosensor. There is also a heater inside the chamber for
measurement of TEC polarity. There is also a LED for visual control of measurements status.
USB connector for connection to a PC, and connector for a cable for external TEC measurements
are located on the back of the device.
T0C
Hbridge
Precision
current
source
Instrumentation
amplifier
switch
DAC
ADC
Microcontroller
Internal
connection
Heater
External
connection
switch
USB
driver
current
source
Z-meter: back view and functional scheme
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Z-Meter DX4090
4. WORKING WITH Z-METER
4.1. External connections.
Connect Z-meter to USB port of your PC.
Connect the cable for external measurements to the connector Ext if you plan external
characterization of TEC(s). Otherwise this cable should not be disconnected to the Z-meter.
4.2. USB Drivers Installation
Install USB drivers using enclosed CD/flash. The latest versions of drivers are also available at
http://www.ftdichip.com/Drivers/VCP.htm .
Installation procedures for a specific version of Windows may be also found at
http://www.ftdichip.com/Support/Documents/InstallGuides.htm
USB Serial Converter should appear in the Windows Device Manager after successful installation.
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4.3. Software Installation
Insert the CD/flash to a PC and start the Setup program.
The window of the standard Windows installer will appear – see below.
Click “Install” and proceed according to the installer directions. Remember at least 20 MB of a space
should be initially available at selected logic disk, and that the size will increase when you’ll add new
TECs to a database with measurement results.
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Z-Meter DX4090
5. MEASUREMENT OF TE MODULES PARAMETERS
TECs and Z-meters must be kept at ambient conditions expected during tests for at least of one
hour before any measurement.
If any Z-Meter was stored at / subjected to temperatures below +10°C before measurements, it
must be kept at expected ambient test conditions for at least 2 hours.
5.1. TE Modules Connection
5.1.1. Measurements of TECs in internal chamber.
Open the cover of the Z-Meter.
Connect TEC to terminals firmly (see left).
Close the cover and run the Z-Meter program.
5.1.2. External TEC measurements
Connect your TEC firmly as shown below.
Ensure minimum possible air convection in the area of measurement. It is recommended to place
the TEC as close to the Z-meter as possible keeping internal chamber opened. Remember temperature
sensor is located in the chamber and considerable difference of TEC and thermosensor’s temperature
will result in mistakes in measurements.
Note TEC polarity check option must be switched off in case of external measurements.
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5.2. Working with Program
The Z-meter must be plugged-in to PC before running the Program.
The following windows will be displayed one after another in case you run Z-meter program for the
first time, see below :
If the “DEVICE NOT FOUND” message pops up, please make sure the device is properly
connected. Also check whether the USB drivers have been properly installed and repeat USB driver
installation procedure if required ( see 4.2. above).
5.3. Program Main Window
The main program window is shown in the screenshot below.
Result
field
Dynamics
field
Corrections
field
Device
info
field
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Control
field
Type connector &
Use Check Polariry
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Z-Meter DX4090
Its functional structure is the same for three Z-Meter measurement options:
 Single-stage TE module;
 Single-stage TE sub-mount;
 Two-stage TE module.
5.3.1. Menu Bar
There are four items in the Menu bar.

"File" is used when it is necessary to reconnect the Device or
exit.

"Options" allows:
1) adding/editing a TE module type;
2) selecting a TE module (TEC) database;
3) choosing a TE module (Cooler) type;
4) enabling/disabling check polarity TE module (internal TEC
connection only)

"History" allows switching from current measuring
results to database with previous measurements.

"Help" provides information concerning the Z-Meter software
5.3.2. Reference Bar
There are two fields in the Reference bar.
The field "Cooler type ID" allows selecting a TE module
type to be tested.
The field "Reference T" serves for the reference
temperature input. The values R and ∆Tmax displayed will be
recalculated to this temperature. The temperature step is 0.1
K.
You may also choose a value from
standard reference temperatures which are 20°C or 30°C, or ambient.
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5.3.3. Functional Fields
There are four functional fields in the main window:

Control” field presents the following test parameters:
electric current, total time of measurement, time step.
The button "Measure" starts the measuring procedure.
Dynamics field depicts the chart window of the
Seebeck voltage U(t) temporal behavior telemetry

It also indicates obtained values of:
1) Time constants at different current polarities,
2) Z at different current polarities

Corrections field shows the important calculated
corrections values which will be used for calculation of
them main performance parameters like, for example, Z
(see Chapter 7 for details). .
Following possibilities of a correction exist :
1) Default - using of the calculated corrections (only for the TE modules fully described in the
database);
2) Manual - using a User's own coefficient value A, manually inputted;
3) None – no use of any correction.

Results field contains the following measured/calculated results:
1) Electrical AC resistance R of the TE module;
2) Ambient temperature Tambient;
3) Figure-of-Merit Z of the TE module (for two polarities and averaged);
4) Maximum temperature difference ∆Tmax of the TE module (for two polarities and averaged);
5) Time constant  of the TE module (for two polarities and averaged).
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Z-Meter DX4090
5.4. Measurements of R, Z, 
5.4.1.
Temperature Setting
Z-meter allows re-calculation of the main TEC parameters to various temperatures (see Chapter 7).
The RMT's standard temperature is 27°C, other manufacturers may apply their own values. The most
convenient ambient temperature to which the parameters are recalculated may be selected from a
“Reference T” list of entered manually.
5.4.2.
TE Module Type
Select a "Single-stage" or a "Two-stage" option following " Option>> Cooler Type". Note if no option
is chosen, corrections are set zero.
If serial number of the testing is known or identified (in a case of testing of RMT TECs) set the s/n using
Cooler type ID from listed database at reference Bar
In the case software will extract default corrections factors for the particular TEC type in the field of
corrections
If type is unknown then the state is “Default”.
If the TEC type is not listed into software database one can stay correction coefficient as 1, or to set own
corrections coefficients if they are known of can be calculated.
Automatic notice will appear if any TEC parameter required for further calculations is missed. Add
correspondent parameter to the database.
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If necessary TEC type is absent in the list, add module parameters to the database manually (see
Chapter "Database Update").
5.4.3.
Corrections Field
Attention!
If no information on parameters of tested TEC is available in the database, no
corrections/coefficients will be used in calculations of TE module parameters by default.
“TE Cooler Type” field will change to DEFAULT in this case.
With all TEC parameters available, the corrections as well as their equivalent coefficient А are taken
into account by default (see Equation 7.3.1). The corrections are specified in the Table below. It is
possible to switch particular correction on/off by correspondent radio button pairs. The Results window
fits the changes automatically.
Symbol
bT
b
th
Description
Allows for the inequality of the ambient
temperature and the average
temperature of a TE module
Allows for additional heat fluxes
between pellets
ba
Allows for external heat fluxes
br
Allows for additional electrical resistance of leading wires
Comments
For single-stage
modules only
For single-and twostage modules
For two-stage
modules only
For single-and twostage modules
In other words, any user is given an opportunity either to take into account the corrections via the
calculated values selected by a User and their equivalent coefficient А (by default), or to suggest one's
own value of A, or to refuse all the corrections.
5.4.4.
Parameters for Header Thermal Resistance
Z-Meters also allow characterization of TE cooler sub-assemblies by choosing correspondent option in
the Manu. In this case, however, following parameters should be available/ added:
1) the header material thermal conductivity;
2) the header base thickness;
3) the mounted TE module fully described in the Z-meter database.
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Z-Meter DX4090
5.5. Measurement Procedure and Notes
Reference Temperature
Set required reference temperature at reference Bar.
Default - 27 °C (300K).
Parameters of measurement
In “Control” field one can set parameters of measurement
Working Current
Recommended value is 1% of Imax according to specification of examined TEC unit. If it is not known –
use default – 5mA for the beginning.
Time of measurement
Set the total measurement time. Recommended value – more than 5-6 of time constant of the TEC. If
the value is unknown set stay default – 10 second for the beginning.
Time step
Recommended value – 20 millisecond.
Measurement cycle is started simply clicking “Measure” in the Program Main Window.
Attention! The temperature of a TE module changes slightly owing to hands touching.
Besides, the measuring procedure induces a slight TE module average temperature
increasing. So keep a pause of at least 3x measured time constant before any new
measurement. It is usually 30 sec on average. This time is usually enough to stabilize
the TE module temperature.
The message:
appeared shortly after clickinmg “Measure” means that either:

open circuit inside the TE module,

short circuit inside the TE module.
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Note the last case is hardly possible in practice according to RMT’s experience. Therefore, open
circuit is more likely the reason. Double-check the terminals for proper contacting TEC. Retry measuring.
Occurring of the message indicates on TE module failure/malfunction.
Attention! Selection of a too higher TEC control current (see the Main Window) may
result in exceeding of a full scale of ADC used. The message as shown below will be
generated automatically. In such a case, select the value recommended for
measurements and try again.
If everything is OK at Graph field you will observe curves of Seebeck voltage measurement in time
under applied working current.
After two curves appear (direct and reversed current measurement) the software will calculate all
measured parameters
Reference resistance
temperature)
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(at
reference
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Z-Meter DX4090
As mentioned above, the DX4090 Meter may be also used for measurement of AC resistance in
coolers with more than two stages. To do this, leave the "TE Cooler Type" unselected (Default Type in
the "TE Cooler Type" field). Insert a TE module into the DX4090 Meter and click the "Measure" button.
Note you must ignore all the results except the resistance value in such a case.
5.6. History
5.6.1. File
The results of each measurement are stored in the file.
You can view or clear it using the "File" command.
The history file is created in the "/History"l folder of the "/Zmeter" directory during every measuring session after the first
successful measurement. ("Measuring session" means the
period between the first successful measurement and the
program exit). The history file name has the form of the date
and time of the history file creation. "Comment" field on the top
of the "History" window allows adding of additional comments
to history files.
If you need to save the "History" file under other name, use the "Save As" command.
The "New" command closes the current history file and opens a new one with no data.
Data arrangement in the "History" window is represented below.
The "Chk" field is assigned for records marking. Note only marked records will be copied on a printer
under the "Print" command. The marking/unmarking is performed with the mouse left button click on the
appropriate field. The default record state is "Marked".
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5.6.2. Options
If menu item "Auto Save" is checked, the "History" file will be saved automatically.
5.6.3. Report
With the "Print" command you can make the hard
copy of the "History" file on a default printer.
Submenu "Export" will help you to keep a «History»
file in various formats:
The example of Preview Report is shown below.
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Z-Meter DX4090
5.7. TE Modules Database Update
If the parameters of any TE module are not available in the database, you can add them by yourself.
The full set of parameters consists of:
1) TE module cold and hot sides dimensions;
2) Pellets number (for a two-stage TE module the pellets numbers ratio);
3) Pellet cross-section;
4) Pellet height;
5) Leading wires material,
6) Leading wires length,
7) Leading wires cross-section.
Choose the database you want to change (see the figure above, example only). Select the "File" ->
"TEC Base Editor" command from the "Main" menu. The window titled "Add TE cooler" will appear.
There are two input boxes in the window: "Cooler" and "Leads". All or a few fields may be already
filled in. Enter correct/required parameters by yourself when required.
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The contents of "Cooler ID" field are not used for calculations. You can fill any information in this
field.
You can also edit or delete a TE module existing in the database. To do it just select the TE module,
make appropriate changes in the data and click on the "Add/Modify" button. To remove the TE module
from the database, select it and click on the "Delete" button.
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6. TEC DYNAMICS PROCESSING
6.1. Time Constant Measuring
Let us consider a single-stage TE module. The ambient temperature is Ta. At a certain moment
electric current is applied to the module. The differential equation describing transient dynamics for a
pellet of the TE module can be presented as the following exponential superposition:
(6.1.1)
where
∆T(t,x)=T-Ta, T is temperature of the pellet point located at a time t and a generalized coordinate х,
Un and mn are the eigenfunctions and eigen-values,
An are thermal amplitudes,
∆Tst(x) is stationary ∆T value.
The solution (6.1.1) analysis yields that the cooling process can be divided into two stages: irregular
and regular. The first one is dictated by the initial moment's conditions and is described by a multiexponential interference. This phase fades out rather quickly and in case TEC pellets thermal
conductance is high enough, the temporal behavior can be characterized by the only exponent, i.e for all
possible n:
(6.1.2)
The theory yields the following expression for the time constant =1/mmin of a single-stage TE
modules:
(6.1.3)
Here C1 ,C2 are TE module cold side and hot side heat capacities,
α - TE material Seebeck coefficient,
 - TE material thermal conductivity,
N - TE module pellets number,
L - pellets height,
s - pellets cross-section,
j - electric current density.
As Eq. (6.1.3) shows,  calculation is stumbling because in practice the values involved are never
known with accuracy required. The Z-meter allows measuring time constants of single-stage TE
modules and estimating those of more-stage ones.
6.2. Interpolation Results
The procedure of handling the time constant measurement data is as follows.
The temporal behavior of a single-stage TE modules temperature difference is measured via the
Seebeck voltage that is a corresponding proportional value:
(6.2.1)
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Z-Meter DX4090
TE module time constant τ
is the time during which TE
module temperature
difference ∆T grows from 0
to 0.63∆Tst (Tst is steady
state T value) at electric
current turned on.
RMT Ltd
For a two- or more-stage TE module this simple ratio is not
applicable. However the time constant can be estimated by the
temporal dependence of the Seebeck voltage and the approach for
obtaining the stationary voltage values is the same.
The measuring procedure is carried out both for two electric
supply polarities. The data collection duration and time step can be
varied. The measuring time duration and step can be varied, too.
The measuring chart window is presented on the Figure
below.
Measuring window of TEC dynamics
The obtained experimental data is then fitted by the following function:
(6.2.2)
The exponential regression is based on the method of least squares. As its outcome, the procedure
provides the time constant  and the stationary Seebeck voltage Ustα.
7.
FIGURE-OF-MERIT Z MEASURING
7.1. Single-stage TE Module Z
Among the parameters (R, Z, ∆Tmax, τ), measured by the Z-Meter the AC resistance R is the only
measured directly. The R measurement method is described in the Section "AC Resistance
Measurement".
The determination of the Figure-of-Merit Z and the maximum temperature difference ∆Tmax of a TE
module implements an indirect method, which allows avoiding labour-consuming thermophysical
measurements. This approach is based on the Harman method.
The Figure-of-Merit is one of most important parameters of a TE module. In a simplified form it may
be defined as:
(7.1.1)
Where:
α − TE material Seebeck coefficient,
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R − TE module pellet electric resistance,
k − TE module pellet thermal conductance.
Hereinafter we deal with the stationary mode values only ( if not
mentioned otherwise, see Section 6.1). The base equations that describe a
single-stage TE module thermal balance are as follows:
(7.1.2)
where
I
- electric current,
R - electric resistance of a TE module pellet,
T0 - TE module cold side temperature,
T1 - TE module hot side temperature,
Ta - ambient temperature,
N - TE module pellets number,
a0 - heat exchange coefficient for the cold side,
a1 - heat exchange coefficient for the hot side,
k' - efficient thermal conductance of a pellet allowing for additional heat fluxes between the pellets.
We assume that the heat exchange coefficients meet the following requirements:
(7.1.3)
We also suppose that electric current is small:
(7.1.4)
We recommend the measuring
current
See Imax values in
the TEC specifications
To the accuracy of the first-order infinitesimals of the values (7.1.3) and (7.1.4), we obtain for Z:
(7.1.5)
Where
Uα = Nα(T1 - T0) is TEC Seebeck voltage,
UR = NIR is TEC Ohmic component of the voltage.
The ratio of the voltages Uα and UR in Eq. (7.1.5) must be averaged for two directions of the current
(the index av=average), as it eliminates expressions depending linearly on the current and allows
extracting the corrections bth, br, bT.
The value bth is the correction for additional heat flux between the pellets; br is the correction for
leading wires electric resistance; bT is the correction allowing for inequality of the TE module average
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temperature and the ambient temperature.
The values a0, a1 are estimated with account of free convection in the air and of thermal radiation:
a0,1=(αconv+αrad)S0,1, where αconv, αrad are thermal exchange coefficients of convection and of heat
emission calculated for each TE module individually, S0 and S1 are the surfaces of the cold and hot sides
of the TE module tested.
Eq. (7.1.5) remains fair if inequalities (7.1.3) are modified as:
(7.1.6)
That means that the method allows finding the value Z of a TE module when the heat exchange on
one side of the module is intensive enough. Therefore, the Z-Meter enables testing of a TE subassembly: TEC mounted on a header. In this case the value a1 is the header thermal resistance
(calculated by the Program).
The measured Z of a single-stage TE module allows estimating ∆Tmax of the module at the hot side
temperature Т1:
(7.1.7)
7.2. Two-stage TE Module Z
For a two-stage TE module Z can be estimated with the help of the Harman method and can only be
regarded as a criterion of an average quality of pellets if certain requirements are met.
Here are heat rate equations for a two-cascade TE module:
(7.2.1)
Here
T0,1,2 substrates temperatures,
Ta - ambient temperature,
N1,2 - numbers of pellets on the stages,
a0,1,2 - heat exchange coefficients for the cold, hot and medium
substrates, respectively.
Let us assume that the ratios of the heat transfer coefficients a0 and a2 from the surfaces S0 and S2
to the pellets number N1, N2 are the same:
(7.2.2)
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The first and third equations of (7.2.1) can be written as:
(7.2.3)
If temperature differences on the cascades can be considered
equal:
∆T1=∆T2 ,
(7.2.4)
we obtain:
(7.2.5)
In real testing Eq. 7.2
is not rigorous, and Z
7.2 is only a relative
criterion of a TE module
quality.
Here bth is the correction for additional heat flux between the pellets;
ba is the correction for external heat fluxes; br is the correction for leading wires electric resistance. The
value a is estimated by the software taking into account free convection in the air and heat emission.
Averaging the voltages ratio (7.2.4), though mathematically not obligatory, is carried out similarly to
a single-stage module case for accuracy purposes.
7.3. Alternative Correction
It is convenient sometimes to reduce all the corrections discussed above to a certain coefficient А.
Then Eqs. (7.1.5) and (7.2.5) can be written as:
(7.3.1)
The coefficient А can be also obtained empirically by correlating directly measured ∆Tmax and the
value obtained by Z-Meter.
8. MEASURING PROCESSES
8.1. AC Resistance Measurement
AC resistance is measured by applying a small AC signal to TE module. The AC is generated by a
“Commutator” (swtich), which periodically (with 50% duty circle) reverses a circuit of the reference
current Im. The “Commutator’s” simplified diagram is shown below.
If there is no input signal, the output voltage of the instrumentation amplifier equals Em/2, where Em=
4.096 V.
AC R testing simplified diagram
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RMT Ltd
Output signal of instrumentation amplifier when AC R is tested
During AC resistance measurement the output voltage of the instrumentation amplifier is sampled
and measured by a 12-bit ADC each time before reversing the current Im.. The sampling points are
marked as ti in Fig. 8.1.2. The voltage drops on TE module for the positive signal (Upi) and negative
signal (Uni) are used for a TE module resistance (R) calculation by the following formula:
(8.1.1)
where
AV - voltage gain of the instrumentation amplifier;
n - total number of readouts per measurement.
Typical values of parameters in formula (8.1.1) are:
Im
= 2 mA
AV
= 5 or 50
n
= 50
8.2. Measurement of U and Uα Telemetry
During measurement of the parameters U and Uα, a small current IT is applied to TE module
periodically (with 50% duty cycle).
Two successive measuring sessions are necessary to obtain the U and Uα values at different testing
current polarities.
Testing current and voltage schematic temporal behavior
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Z-Meter DX4090
8.3. Voltages Measurement for Testing Z
Equations (7.1.5) and (7.2.5) contain both UR and Uα. These are the voltage values referred to the
time at which the process becomes steady.
Thus, the Seebeck voltage Uα in Eqs. (7.1.5), (7.2.5) is equal to the stationary value Ustα obtained by
the interpolation procedure (see Eq. (6.2.2)).
The Ohmic voltage drop UR is also calculated with reference to the steady-state time t. It should be
done for the reason the TE module resistance R undergoes a change due to a slight evolution of its
average temperature. At the current IT=0.01Imax it may have about 1-1.5 % growth. So, the value UR is
resulted from the following averaging over the last 10 time points of the testing procedure at one current:
(8.3.1)
Make sure the measured TE module has reached the steady state. To assess it, the telemetry
capability is available (see dynamics window)
8.4. Checking of TE Module Polarity
To verify a TE module polarity the Z-Meter involves a procedure of a short-time heating of the
bottom substrate of the module when finishing the procedure of voltage measuring on "direct" polarity.
The averaged voltage U'α measured while heating is compared with the value Uα averaged over last
10 points of Uα:
(8.4.1)
If the TEC polarity is right:
(8.4.2)
In case of the polarity confused:
(8.4.3)
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Z-Meter DX4090
9.
RMT Ltd
MAINTENANCE
The Z-Meter does not require any particular maintenance or service.
Nevertheless if for any reason you feel doubtful about the device accuracy, you can check it by
measuring a precision resistor instead of a TE module.
The “R-meter” program should be used. We suggest measuring a resistor of 5 to 20 Ohms. Measure
the resistor by “R-meter” program and digital multimeter with accuracy the same or better than 3 decimal
digits.
Compare the data obtained. If the difference in the resistance values is within 0.5%, the Z-Meter can
be further used for measurements.
WARRANTY
RMT LLC warrants that the Z-Meter, if properly used and installed, will be free from defects in
material and workmanship and will substantially conform to RMT’s publicly available specification for a
period of one (1) year after date of the Z-Meter was purchased.
RMT LLC also provides a 3-month warranty for the following parts and components included in the
standard delivery set of the product: the cables, program disks and documentation
If the Z-Meter fails during the warranty period RMT will repair the Z-Meter or replace it or its parts.
For the warranty support a Consumer can address to the office of the company RMT or its sales
representative.
The product repaired or replaced in whole or in part, will have the warranty period counted as one
(1) year from initial shipment but not less than 3 months upon shipping of repair/repalcement.
TECHNICAL SUPPORT
For the technical support and repair within and after the warranty period, please, address to the
office of the company RMT or its sales representatives:
In Russia and CIS
RMT Ltd
46 Warshavskoe shosse, Moscow 115230, Russia
Phone: +7-499-678-2082
Fax:
+7-499-678-2083
e-mail:
info@rmtltd.ru
In Europe, the USA and other countries
TEC Microsystems GmbH
Schwarzschildstrasse 3, Berlin 12489, Germany
Phone: +49-(0)30-6789-3314
Fax:
+49-(0)30-6789-3315
e-mail:
info@tec-microsystems.com
Fax:
+49-(0)30-6789-3315
e-mail:
info@tec-microsystems.com
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