DATASHEET

SMT172

last update

maart 20, 2017

reference

V14

page

6

Measurement with improved accuracy

This part of the datasheet of the SMT172 provides information how a temperature can be measured with a

higher accuracy than what is specified in the datasheet.

How about

There are two reasons why the accuracy of ±0.25°C (

-10°C to 100°C) has been specified in SMT172:

1.

A linear equation, which is compatible with SMT160 has been used for duty cycle versus

temperature. Higher order system errors remain.

2.

Due to the special design skill, one complete measurement is the average of 8 periods (or a

multiple of 8 periods). The specified accuracy in the datasheet is valid for all kinds of averaging

methods.

If a more accurate measurement is required, a more sophisticated interpretation of the output signal is

needed.

The better accuracy can only be achieved when:

1.

Equation (2) is applied to obtain the valid duty cycle,

2.

A second order equation is applied to translate the valid duty cycle to a temperature:

= −1.43

+ 214.56

− 68.60

This second order equation can better interpret the valid duty cycle to temperature, and thus a more

accurate result can be achieved. The equation corrects for the typical error curve versus the temperature

as in the graph on the previous page.

Performance characteristic

Application Information

Temperature measurement

The SMT172 measures the temperature of its bipolar transistors with high precision. Due to the great

SMT172

SMT172