Introduction to the Thermal Resistance Analyser TRA- 2:7




The TRA-2:7 is a Static Thermal Resistance Analyser for Diodes in a series of such equipments made by Challenge Innovations.

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The Static Thermal Resistance parameter is a measure of the performance of a diode  to a given dissipation waveform when it has reached steady state conditions.

 The TRA-2:7 design provides;

 - Bipolar Constant Current source capable of +/- 100 Amps peak used as the power dissipation source. One side of this source is earthed.

 - Waveform choice of;

                - Positive pulse train with 0.5 to 500.0 msec. separately

                  programmable ON and OFF times,

                - Negative pulse train with similar times,

                - Positive half sinusoid, choice of 50 Hz or 60 Hz free running

                  and 60 Hz sync. to local mains,

                - Negative half sinusoid, choices as above,

                - Full sinusoid, choices as above.

                Note that all these waveforms are generated using software running

                in the internal microcomputer.


- Monopolar Constant Current source capable of +1mA to +100mA, used for the junction temperature measurements.   This source is completely isolated from ground to +/- 100V.

 - Measurement Unit consisting of an 8 input multiplexer driving a 16 bit AD-converter. The first 4 inputs are via +/- 200V common mode input  amplifiers (INA117/AD629). This unit is used to sample all  the voltages necessary for the test and check sequences. Every 1 second for the duration of the power dissipation, the values of  V1(once only at the start),V2, Vf  and thermocouple temperature are measured and the values displayed.

 There is a facility for calibrating this unit with an external voltage source entered into front panel test point #7.

  -  Three ‘T’ type thermocouple input with a range of 0 to 200 deg.C  used for ambient (ta), lead (tl) and case (tc) measurements. The tip can be +/- 50V from earth.

 -  All parameters brought out to the front panel via a standard Challenge Innovations DUT connector  ready to accept     a wide range of Test Heads.

 -  All internal control by microcomputer ( Intel 188 ) programmed in ‘C’.

 -  External control by standard  PC running the latest “Windows “based software.

All the usual facilities are provided including EXCEL, WORD etc.

                                 Two software packages provided;


                                - Aid for generation of “K-Factor” on diode with “to do” list

                                for up to 10 voltage/temperature measurements. Option to

load all points into EXCEL for drawing the graph.


                                - Static Tjc Testing package, which provides parameter

                                set-up  facility and display of the measured values.

The main screen is shown;

range322.jpg (24814 bytes) The top half shows the parameter values used. The “Change” button will show the parameter set-up screen below.

The bottom half shows the test results. All are updated every second as the test proceeds.

When the Operator is satisfied that the results have reached “Steady State”, the test is stopped. The usual facilities for saving, printout etc. are available.


The test programme set-up screen. All the Tester’s parameters are available.


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The TRA-2:7 is supplied with a complete set of electrical drawings and full operating and programming information.        The Block Diagrams which explain the operation of this TRA-2:7 Tester are;

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 The functions available from the front panel DUT connector,

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The timing diagram of the waveforms provided by the  waveform generator and the general test sequence.

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 The sampling details used for both Vf and V1 / V2.

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 The power sampling details for the calculation of the sinusoid true power value.

 There many options and Tester types available for testing Thermal Resistance on diodes and similar devices. Please contact Challenge Innovations or their Agents for details.

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