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Entry type: FAQ Entry ID: 15398450, Entry date: 04/01/2014
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With the LOGO!, how do you have a digital output switched as a function of a temperature threshold value?

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Instructions
To have a digital output switched as a function of the temperature threshold value you need a LOGO! basic device, an analog expansion module AM2 PT100 or AM2 RTD, a PT100 temperature sensor and the latest version of the LOGO!Soft Comfort software. The analog expansion module AM2 RTD also supports the connection of PT1000 sensors. Visit the following link for a free upgrade to the latest version of LOGO!Soft Comfort:
Upgrade zu LOGO!Soft Comfort.

The numbering of the analog inputs in the control program depends on the analog inputs set on the LOGO! basic device.

With the LOGO! 12/24V and 24V versions, there are already two analog inputs of 0-10V integrated on certain basic devices. With device series 0BA6 onwards, certain basic devices of the LOGO! 12/24V and 24V versions also have four integrated analog inputs (0-10V). With the LOGO! 230V versions, the basic devices only have integrated digital inputs. Using the menu on the LOGO! controller or in the LOGO!Soft Comfort software, you can set whether you want to use two or four integrated analog inputs. The two or four integrated analog inputs must be counted when assigning the analog inputs for the analog expansion module AM2 PT100 or AM2 RTD.  

  1. For the LOGO! 230V, 24RC and 24RCo versions, the first analog input of the first analog expansion AM2 PT100 or AM2 RTD in LOGO!Soft Comfort is Analog input 1.
  2. For the LOGO! 12/24V and 24V versions, with two integrated analog inputs set on the basic device, the first analog input of the first analog expansion module AM2 PT100 or AM2 RTD in LOGO!Soft Comfort is Analog input 3.
  3. For the LOGO! 12/24V and 24V versions, with four integrated analog inputs set on the basic device, the first analog input of the first analog expansion module AM2 PT100 or AM2 RTD in LOGO!Soft Comfort is Analog input 5.

Note
When connecting an additional analog input to the first analog expansion module AM2 PT100 or AM2 RTD just as well as when connecting additional analog expansion modules to the basic device, each analog input is numbered one after the other in the given order.

Parameterizing the threshold value in LOGO!Soft Comfort

  1. Connect the selected analog input of the analog expansion module AM2 PT100 or AM2 RTD with the analog threshold switch that switches the selected digital output.
  2. Call the Block Properties of the analog threshold switch.


    Fig. 01
  3. Select PT100 as the sensor.
  4. Under Unit you select Celsius or Fahrenheit.
  5. Under Resolution, you select whether you want to measure in full degrees or 10ths of a degree. In the latter case the measured value is multiplied by 10.
  6. Under Threshold, you select the threshold value. If you are measuring in 10ths of a degree, then this must also be taken into account when setting the threshold value. For example, for measurements in 10ths of a degree, for 27.5 °C the analog input gives the value 275. Set the values for the switch-on and switch-off thresholds with a sufficient difference to prevent permanent switching on and off caused by the AD converters. If the value of the switch-on threshold is exceeded, the digital output is switched on. If the value <= the output threshold, the digital output is switched off.
  7. If you want to have the temperature value shown with a message text on a display (LOGO! Display or LOGO! TD), then you must specify 1 for the decimal place in the case of a resolution of 0.1.

Further Information

  • Detailed information about the different types of connection of AM2 PT100 and AM2 RTD analog expansion modules is available in the LOGO! manual (Entry ID: 50074616) in section 2.3.2 "Connecting LOGO! inputs"
  • Additional information about you connect a PT100 sensor to the LOGO! analog expansion module AM2 PT100 or AM2 RTD is available in Entry ID 23671451.

Additional Keywords
PT100, PT1000, AM2 PT100, AM2 RTD, Digital output threshold value

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