Datasheet

DATASHEET

SMT172

last update

juni 1, 2015

reference

V10.0

page

6/9

Measurement with improved accuracy

This addendum to 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>100°C) has been specified in the datasheet of the SMT172:

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

temperature. Higher order system error 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. All the specifications of the SMT172 are valid except for the ones given below. The maximum

accuracy can be achieved with some extra software.

Inaccuracy 0.1 °C -20°C to 80°C for TO18

0.4 °C -45°C to 130°C for TO18

For the plastic types this figures respectively will be 0.25 and 0.8 °C.

This inaccuracy can only be achieved:

1. Accurate method is applied to obtain the average value of the duty cycle

2. A specific second order equation has been applied to translate the averaged duty cycle to a

temperature.

Performance characteristic

Inaccuracy vs. temperature (TO18)

SMT172