IEEE Standard for a Smart Transducer Interface for Sensors and Actuators
Universal Transducer Interface. Universal Transducer Interface Technical aspects and examples.
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Universal Transducer Interface
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Transcript of Universal Transducer Interface. Universal Transducer Interface Technical aspects and examples.
Universal Transducer Interface
Universal Transducer Interface
Technical aspectsand
examples
Universal Transducer Interface
A single chip digitiser for
Resistive sensors
Capacitive sensors
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
E
A
B
C
D
F
Output configuration:- one line
- CS/PD line - Vcc 2.9 - 5.5 V(max 3 mA. Icc).
Gnd
Vcc
PD/CS
Out
Toff Tbc Tcd Toff
Time frame of output signal(10/100 ms)
Universal Transducer Interface
Resistive modeE
A
B
C
D
F
Excitation:
- counter-phase- ± 5 kHz
Vcc
Universal Transducer Interface
Universal Transducer Interface
E
A
B
C
D
F
Vcc
Gnd
Vcc
Vx
Resistive mode
Universal Transducer Interface
Gnd
VxV
V/T
Out
UTI =
- Voltmeter
-V/T converter
Resistive mode
Universal Transducer Interface
E
A
B
C
D
F
V
V/T
Out
Toff Tab Tbc
Output Signal-------------------
Toff=A*Voff
Toff: two periods for synchronisation
Offset measurement
Resistive mode
Universal Transducer Interface
E
A
B
C
D
F
V
V/TTab=A*(Vab+Voff)
Toff Tab Tbc
Output Signal-------------------
Out
Resistive mode
Universal Transducer Interface
E
A
B
C
D
F
V
V/TTbc=A*(Vbc+Voff)
Toff Tab Tbc
Output Signal-------------------
Out
Resistive mode
Universal Transducer Interface
E
A
B
C
D
F
V
V/TEtc.Tcd=A*(Vcd+Voff)
Complete output time frame is about 100 ms (or 10 ms by selection)
Toff Tab Tbc
Output Signal-------------------
Out
Resistive mode
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
Vcd Vde= ----- and also ------ Vbc Vbc
Resistive mode
three signal technique
Resistive mode
Universal Transducer Interface
No offset errors
No gain errors
No temperature drift
No long term drift
WHY?
IN PRACTICE THIS MEANS
Resistive mode
Universal Transducer Interface
high accuracy (15/16 bits)
no offset and gain adjustment
cost effective solution
E
A
B
C
D
F
Example
Rbias
Rref
Pt100Toff=A*VoffTab=A*(Vab+Voff)Tcd=A*(Vcd+Voff)
Tcd-Toff Vcd i*R(Pt100) Pt100M=----------- = ------ = --------------- = ------- Tab-Toff Vab i*Rref Rref
Pt100 measurement
Toff Tab Tcd
Resistive mode
Universal Transducer Interface
E
A
C
D
B
F
Example
Vcd*32 M = --------- Vab
Bridge measurement
A direct releation between the bridge imbalance and the excitation Voltage
Toff Tab Tcd
Resistive mode
Universal Transducer Interface
All kind of resistive elements
Resistive mode
Universal Transducer Interface
A real revolution in Sensor Interfacing
Universal Transducer Interface
digitises not only resistive elements
but also
all kind of capacitive sensors
The next slide tells you
how the UTI scores!
Universal Transducer Interface
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 InterfaceCapacitive mode
CpCp
Cx
i V
I and V are shortcuts for capacitances sono influence of parasitics
preferred solution
inside the UTI of course
a little theory
four pole measurement
Universal Transducer InterfaceCapacitive mode
A = current inputB / F = voltage output
A
B
C
D
E
F
i
Tab TacTad
Tab=A*(Cab+Coff)
Tab = two periods for synchronisation
Coff=internal capacitance
Cab
Universal Transducer InterfaceCapacitive mode
A
B
C
D
E
F
i
Tac=A*(Cac+Coff)
output signal-------------------
All not-used outputs on Gnd.(see four pole measurement)
Cac
Tab TacTad
Universal Transducer InterfaceCapacitive mode
A
B
C
D
E
F
i
Tad=A*(Cad+Coff)
All not-used outputs on Gnd.(see four pole measurement)
CadTab Tac
Tad
output signal-------------------
Universal Transducer InterfaceCapacitive mode
A
B
C
D
E
F
i
All not-used outputs on Gnd.(see four pole measurement)
Cp has no influence dueto four pole measurement
Tab TacTad
output signal-------------------
Universal Transducer InterfaceCapacitive mode
resume calculation in Microcomputer
Tab=A*(Cab+Coff)Tac=A*(Cac+Coff)Tad=A*(Cad+Coff)Tae=A*(Cae+Coff)
Cab is the lowest forsynchronisation(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 Cae
When Cae is reference Cacand Cad are calculated as fraction of Cae(=Cref)
Again the three signal technique to measure thedirect relation between a Cx and Cref
Universal Transducer InterfaceCapacitive mode
Example
A
B
C
D
E
F
Cae
Caf
C1C2
Angle/Tilt sensor
some calculation
C1 C2---- and ----Cae Cae
If C1/C2 needed then
Cae and Caf not critical
Cba left open for sync and offset
Universal Transducer InterfaceCapacitive mode
Example
A
B
C
D
E
FCba left open for sync and offsetCea and Cfa reference capacitor
Pressure sensor
Universal Transducer InterfaceCapacitive mode
Example
B
C
D
A
E
F
+
Exotic application for threecapacitors up to 300 pF
Universal Transducer InterfaceCapacitive mode
Example
D
B
C
A
E
F
MUX
Etc.
MUX
Multiple capacitors measurment setup
Especially designed for level gauging purposes
accuracy over 4 meter better than 0.1 mm
Universal Transducer InterfaceCapacitive mode
VSS
VDD
ABCDEF
Logic control circuit
FrequencyDivider
Driver
Voltage toPeriod
Converter
AMP/C-V/
DividerMUX
UTI
SEL1 SEL2 SEL3 SEL4 CML SF PD
OUT
Block diagram
SEL 1-4 for mode selection
Available in PDIP and SOIC version
Universal Transducer Interface
