Siemens S300 - PT100

alekbeck · May 6, 2009

This is my first time using a RTD element, so i hope some of you can help me.

I am using a PT100 sensor with range -50 - 200 `C. I have set up the analoge card to RTD standar. Acording to the manual the analoge card resitance range is 0-600 kOhm

When scaling the signal, will -50`C = 0 and 200`C= 27648 ?
Or do i have to know the resistance in the element when temperatur is -50 and 200 celsius ?

lbg_dk · May 6, 2009

alekbeck said:
This is my first time using a RTD element, so i hope some of you can help me.

I am using a PT100 sensor with range -50 - 200 `C. I have set up the analoge card to RTD standar. Acording to the manual the analoge card resitance range is 0-600 kOhm

When scaling the signal, will -50`C = 0 and 200`C= 27648 ?
Or do i have to know the resistance in the element when temperatur is -50 and 200 celsius ?

I dont know how simens work but here are the resistance for a PT100. For other temperatur see http://www.jensenelectric.dk/extern/pt100din.htm
-50`C = 80.3063 ohm
200`C = 175.856 ohm

RMA · May 6, 2009

You don't mention which Analogue Input module you're using, but the usual RTD setup is that the raw data you read from the PIW is the Temperature in tenth's of a degree (assuming you've parameterised the module correctly!).

Sparkz · May 6, 2009

You don't have to worry about scaling or range if the RTD module is correctly set up for a PT100.

Like RMA already stated, reading the PIW (=address where the analog value can be read from the RTD module) will give you the measured temperature x 10 as an integer value -> 20.7°C can be read as 207.

alekbeck · May 7, 2009

The input model i choose is 6ES7331-1KF01-0AB0 , 8 analoge inputs: Voltage,current,resistance and temperatur. Any measuring range per channel.

In the hardware setup, i have set up the first 3 inputs to 0-10 V, and number 4 to RTD standard range. (Here i can also choose climatic range) Are the more parameters i have to configure ?

So what you are saying is that if the inncoming signal is 300 , the temperature is 30`C ?

I alway thougt inncoming values from PIW was in REAL format. do i have to convert this signal to INT value ?

seppoalanen · May 7, 2009

It is integer type if you declare PIW (PEW) to int, just divide by 10.
Better way is change it 1'st dint and real, then add 0.5, divide by 10.0 and shange it to dint and move to int.

alekbeck · May 7, 2009

seppoalanen said:
Better way is change it 1'st dint and real, then add 0.5, divide by 10.0 and shange it to dint and move to int.

Huh ? That i did not understand ? This is better than just devide the INT signal by 10 ?

RMA · May 7, 2009

If you just Integer divide by ten you don't round correctly by default. You need to check the remainder in the high WORD of AKKU1 to see whether you need to round up or not.

Adding 0.5 (after converting to REAL) before doing your divide automatically gives you the correct rounding.

mo_eng · May 7, 2009

its depend to resolution your analog cart .for example if you use a 12 bit module you have to scale that 2^12 its equal 0 to 4096 in your case -50=0 and 200=4096

RMA · May 7, 2009

mo_eng said:
its depend to resolution your analog cart .for example if you use a 12 bit module you have to scale that 2^12 its equal 0 to 4096 in your case -50=0 and 200=4096

This statement is rubbish. The value of a Siemens Analogue Input PIW is always left justified. All that changes is the resolution.

Siemens S300 - PT100

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