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Wednesday 23/02//2005

SMARTEC s.a.r.l. (FRANCE)
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Last update : Wednesday 23/02/2005

the Smartec UTI

PRODUCT DESCRIPTION

The Universal Transducer Interface (UTI) is a sensor-to-time signal converter, based on a period-modulated oscillator. Sensing elements can be directly connected to the UTI without the need for extra electronics to interface all different sensor type.

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The UTI can operate in 16 different modes. To obtain accurate results in any of the modes, one reference element of the same kind as the sensor is required. (Note that this reference is already included in resistive bridges, so no external components are required in this mode.)
Two key techniques that form the basis of the a resolution of 15 bits are four wire connection of the sensors (or less) and the "three variable" technique. These aspects of the UTI are explained in depth in several articles you can find in the SUPPORTSHOP.
What this means?. Well, to give you a hint: You can measure a 2pF capacitor at a distance of several meters, with a resolution of 1 FemtoFarad!.
TECHNICAL DESCRIPTION

The UTI provides interfacing for:

Capacitive sensors 0-2pF, 0-12pF, variable range up to 300pF
Platinum resistors Pt100, Pt1000
Thermistors 1 KOhm-25 KOhm at room temperature
Resistive bridges 25 Ohm-10 KOhm with maximum imbalance +/- 4% or +/- 0.25%
Potentiometers 1 KOhm-50 KOhm
Combinations of the above mentioned

In exactly the same way as the unknown sensor signal is measured, both a reference signal and a internal (constant) offset are measured during two additional phases. Continuous auto-calibration of offset and gain of the complete system

is then achieved by processing these values (time signals) by microcontroller software. The output signal of the UTI is very simple and has discrete amplitude (VDD), so it is compatible with any type micro-controller.
APPLICATIONS

The UTI is an ideal component in applications where digital processing - such as rather complicated compensation for temperature coefficients - has to be applied to the data from analogue sensors.
A typical example where this is the case would be a silicon based resistive bridge type pressure sensor.
Measuring the value of small capacitors (2pF for example), at a distance of several meters, is another engineering challenge, one that can relatively easy be solved with our UTI. The Smartec HS10 humidity sensor is an example of such a capacitive sensor.
FAQ LIST

A number of recurring questions have been dealt with on our FAQ page
GOOD ADVICE

If you consider developing an application for the UTI, we strongly advice you to buy our UTI evalution kit first. This way you can get very fast results with your own project and it will help you better understand the complexity of the UTI. Experience shows that it will save you considerable time. To give you a little support in programming a microcontroller, when connected to the UTI, the source code of PIC processor program of this kit has been made available.
SUPPORT

All relevant documentation and files (data sheet, application notes, software etc.) for our products can be downloaded from the SUPPORTSHOP page.