Autor Thema: Temperature reading  (Gelesen 21446 mal)

Offline hardcorepit

  • Newbie
  • *
  • Beiträge: 3
Temperature reading
« am: Februar 21, 2014, 10:35:29 Vormittag »
Hi.
This is my first time with Easy500(any plc) and I'm having problem with temperature conversion.
I'm using PT100 sensor together with LKM224 transmiter which gives me 0-10V output.
Problem I've got is, how to convert values, that comes up in software ( for example 6V and 619 ADC) to Celsius degrees ??
What temperature I'll have , let say at 5V??
Any explanation would be appreciate.
Thanks.

Offline Spellbreaker

  • Full Member
  • ***
  • Beiträge: 196
Re:Temperature reading
« Antwort #1 am: Februar 21, 2014, 12:41:38 Nachmittag »
Hi there!

First of all you have to check what the Transmitter outputs. For example 0-10V as 0-200°C or something like that.

Then, you simply take an LS Functionblock, using your Analogue Input as I1 , and then set X1 / X2 to 0..1023 (Thats your analogue Input in 10 Bit ), and Y1 / Y1 to the Degrees your Transmitter is set up for, for example 0 / 200°C .

Then you'll get the Temperature from the Functionblocks Output.

Greets,

Spellbreaker

Offline hardcorepit

  • Newbie
  • *
  • Beiträge: 3
Re:Temperature reading
« Antwort #2 am: Februar 22, 2014, 09:11:01 Vormittag »
The problem is, that I'm using Easy500 and there's no LS function.......
I've found example of greenhouse control for Easy500 :
A01 = I07 ≥ 6.0V = 619 (= 19 °C Blinds down)
A02 = I07 ≥ 5.8V = 599 (= 17 °C Heating OFF)
A03 = I07 ≤ 5.6V = 578 ( = 15 °C Blinds up and heating ON)
So somehow they calculate that temperature.
Is it because they base on thermistor sensor instead of PT100?
Transmitter range -30 to 70.
Many thanks.

Offline wer

  • Full Member
  • ***
  • Beiträge: 148
Re:Temperature reading
« Antwort #3 am: Februar 22, 2014, 15:58:39 Nachmittag »
First: excuse my bad english.
Second: What temperature you have at 5V, ist not a funcionality of the easy500 but of your transmitter. Is the transmitter range -30 to +70 degrees or what ever?
Third: What do you want to do with the value in the easy500? then we can look for the easy500 function.

Offline hardcorepit

  • Newbie
  • *
  • Beiträge: 3
Re:Temperature reading
« Antwort #4 am: Februar 24, 2014, 07:17:04 Vormittag »
Is the transmitter range -30 to +70 degrees or what ever?
Third: What do you want to do with the value in the easy500? then we can look for the easy500 function.

Transmitter range is -30 to +70 degrees, output  0 to 10V.
I want to be able to read temperature base on Easy reading which is for example:
6V   619 (adc).
I need to know 3 different temp. 15,20,25 degrees.
Do I have to physically measure that temperature?
Thanks.

Offline wer

  • Full Member
  • ***
  • Beiträge: 148
Re:Temperature reading
« Antwort #5 am: Februar 24, 2014, 14:04:16 Nachmittag »
Your complete measuring range is 100 °C. That means, you have 10°C per 1V. So you have 60°C at 6V wich is +30°C.
For your function you use (in German) the "Analogwertevergleicher/Schwellwertschalter".
The range of 0...10V (-30...+70°C) is equal 0...1023 digit.
For the limit values you need the following constants:
15°C - 460
20°C - 512
25°C - 563