# Cypress Developer CommunityTM

## why temperature scale?

Summary: 8 Replies, Latest post by Stub for 42107979 on 21 Jan 2013 12:09 AM PST
User
19 posts

In the RTD example project provided in PSoC Creator 2.1,what is the significance of using the temperature scale in 'main.c'?

User
9279 posts

A PT100 has a temp range of -200°C to +850°C which is superiour to any semi-conductor sensor. Together with the calibration to get rid of the non-linearities a max precision of 0.01°C within an interval can be archieved.

Have a look into the component's datasheet, under the header "General" you'll find a short description what the component is and what it is good for.

Happy coding

Bob

User
7646 posts

At first I thought it was to get to volts as the RTD is 100 ohms. Eg. its actually

a scale factor for the RTD not being 1 ohm. But I am not sure. Contact the

author of the ap note, and re-post here the answer.

Praveen Sekar [pfz@cysemi.com]

Regards, Dana.

User
19 posts

Poorva,

There are 2 projects with AN70698. 1. RTD temperature measurement, 2. Broken RTD reconfiguration

Which line of code in main.c are you referring to?

Regards,

Praveen

User
7646 posts

I can't speak for original poster but in PSOC 3 RTD Example project in

Creator, line 28, there is a define -

#define TEMP_SCALE (100u)

and used line 140 -

rtdTempDisp = (float) rtdTemp / TEMP_SCALE ;

Regards, Dana.

User
19 posts

Hi Dana,

Regards,

Praveen

User
7646 posts

In Creator, an example project, 5.1

Regards, Dana.

User
19 posts

Praveen Sir,

The RTD temperature measurement project.Lines 28,29 and 140 in main.c

User
19 posts

Poorva/Dana,

The RTD_GetTemperature() API takes resistance in milliohms as argument and returns temperature in 1/100th of a degree celcius.

The temperature scale and resistance scale aid in converting temperature in 1/100th of a degree celcius to degree celcius and resistance in milliohms to resistance in ohms respectively

Regards,

Praveen