1. Universal Transducer Interface

2. Universal Transducer Interface Technical aspects and examples

3. Universal Transducer Interface A single chip digitiser for Resistive sensors Capacitive sensors

4. The one chip digitiser Configuration of output signal Excitation for resistive sensors Selfcalibrating by three signal technique Measuring capacitive sensors without parasitics Universal Transducer Interface

5. EABCDFEABCDF Output configuration : - one line - CS/PD line - Vcc 2.9 - 5.5 V(max 3 mA. Icc). Gnd Vcc PD/CS Out ToffTbc TcdToff Time frame of output signal (10/100 ms) Universal Transducer Interface

6. Resistive mode EABCDFEABCDF Excitation: - counter-phase - ± 5 kHz Vcc Universal Transducer Interface

7. EABCDFEABCDF Vcc Gnd Vcc Vx Resistive mode

8. Universal Transducer Interface Gnd Vx V V/T Out UTI = - Voltmeter -V/T converter Resistive mode

9. Universal Transducer Interface EABCDFEABCDF V V/T Out ToffTab Tbc Output Signal ------------------- Toff=A*Voff Toff: two periods for synchronisation Offset measurement Resistive mode

10. Universal Transducer Interface EABCDFEABCDF V V/T Tab=A*(Vab+Voff) ToffTab Tbc Output Signal ------------------- Out Resistive mode

11. Universal Transducer Interface EABCDFEABCDF V V/T Tbc=A*(Vbc+Voff) ToffTab Tbc Output Signal ------------------- Out Resistive mode

12. Universal Transducer Interface EABCDFEABCDF V V/T Etc. Tcd=A*(Vcd+Voff) Complete output time frame is about 100 ms (or 10 ms by selection) ToffTab Tbc Output Signal ------------------- Out Resistive mode

13. A direct relation between Vcd and Vbc without offset Called the three signal technique Universal Transducer Interface Resume Toff= A*Voff Tbc=A*(Vbc+Toff) Tcd=A*(Vcd+Voff) Tde=A*(Vde+Voff) Calculation in Microcomputer Tcd-Toff A*(Vcd+Voff)-A*Voff ------------= ---------------------------- Tbc-Toff A*(Vbc+Voff)-A*Voff VcdVde = ----- and also ------ VbcVbc Resistive mode

14. three signal technique Resistive mode Universal Transducer Interface No offset errors No gain errors No temperature drift No long term drift WHY?

15. IN PRACTICE THIS MEANS Resistive mode Universal Transducer Interface high accuracy (15/16 bits) no offset and gain adjustment cost effective solution

16. EABCDFEABCDF Example Rbias Rref Pt100 Toff=A*Voff Tab=A*(Vab+Voff) Tcd=A*(Vcd+Voff) Tcd-Toff Vcd i*R(Pt100) Pt100 M=----------- = ------ = --------------- = ------- Tab-Toff Vab i*Rref Rref Pt100 measurement ToffTab Tcd Resistive mode Universal Transducer Interface

17. EACDBFEACDBF Example Vcd*32 M = --------- Vab Bridge measurement A direct releation between the bridge imbalance and the excitation Voltage ToffTab Tcd Resistive mode Universal Transducer Interface

18. All kind of resistive elements Resistive mode Universal Transducer Interface

19. A real revolution in Sensor Interfacing Universal Transducer Interface digitises not only resistive elements but also all kind of capacitive sensors

20. The next slide tells you how the UTI scores! Universal Transducer Interface

21. Cx Cp Parasite Cp parallel to Cx Coax cable two pole measurement Measurement is disturbed by cable capacitance not preferable a little theory Universal Transducer Interface Capacitive mode

22. Cp Cx i V I and V are shortcuts for capacitances so no influence of parasitics preferred solution inside the UTI of course a little theory four pole measurement Universal Transducer Interface Capacitive mode

23. A = current input B / F = voltage output ABCDEFABCDEF i TabTac Tad Tab=A*(Cab+Coff) Tab = two periods for synchronisation Coff=internal capacitance Cab Universal Transducer Interface Capacitive mode

24. ABCDEFABCDEF i Tac=A*(Cac+Coff) output signal ------------------- All not-used outputs on Gnd. (see four pole measurement) Cac TabTac Tad Universal Transducer Interface Capacitive mode

25. ABCDEFABCDEF i Tad=A*(Cad+Coff) All not-used outputs on Gnd. (see four pole measurement) Cad TabTac Tad output signal ------------------- Universal Transducer Interface Capacitive mode

26. ABCDEFABCDEF i All not-used outputs on Gnd. (see four pole measurement) Cp has no influence due to four pole measurement TabTac Tad output signal ------------------- Universal Transducer Interface Capacitive mode

27. resumecalculation in Microcomputer Tab=A*(Cab+Coff) Tac=A*(Cac+Coff) Tad=A*(Cad+Coff) Tae=A*(Cae+Coff) Cab is the lowest for synchronisation (left open in practice) Tab=A*(Coff) Tac-Tab A*(Cac+Coff)-A*(Coff) ----------- = ------------------------------ = Tae-Tab A*(Cae+Coff)-A*(Coff) Cac Cad ----- and similar ------ Cae When Cae is reference Cac and Cad are calculated as fraction of Cae(=Cref) Again the three signal technique to measure the direct relation between a Cx and Cref Universal Transducer Interface Capacitive mode

28. Example ABCDEFABCDEF Cae Caf C1 C2 Angle/Tilt sensor some calculation C1 C2 ---- and ---- Cae If C1/C2 needed then Cae and Caf not critical Cba left open for sync and offset Universal Transducer Interface Capacitive mode

29. Example ABCDEFABCDEF Cba left open for sync and offset Cea and Cfa reference capacitor Pressure sensor Universal Transducer Interface Capacitive mode

30. Example BCDAEFBCDAEF + Exotic application for three capacitors up to 300 pF Universal Transducer Interface Capacitive mode

31. Example DBCAEFDBCAEF MUX Etc. MUX Multiple capacitors measurment setup Especially designed for level gauging purposes accuracy over 4 meter better than 0.1 mm Universal Transducer Interface Capacitive mode

32. Block diagram SEL 1-4 for mode selection Available in PDIP and SOIC version Universal Transducer Interface

33. Thank you for your attention Ask for a demonstration tel +31 76 520 53 53 SmartecNL@compuserve.com