I am using an I/O field to display a pressure value given by the PLC (s7-1200) on HMI (KTP900 basic)

the value that is showing is correct but every so often in a seemingly random patern it flashes to 0.00 for a couple of seconds and the back to the correct value.

value to display is received by a hmi tag linked to a real plc tag. checked the value during live monitoring on the plc and the value is not flashing to 0. so i can only assume the problem is in the hmi.

Hi Tomshcuu,

Do this happen only with that tag and I/O field? Have you tried to creat a new I/O field with the same tag and see if same happens?

I would also follow the next FAQ as it worked for many times when strage behaviour during runtime occured.

https://support.industry.siemens.com/cs/ww/en/view/109778709

Hope it helps

Maby there is a problem with your sensor.

You can check this by creating a trace to see if the tag sometimes goes to 0.0.

rdoliveira

Hello, are you reading a memory area? DB? directly from IO board?

What is the tag reading cycle time on the HMI?

good luck.

 So I have found my problem. I created a function to take the analog input data and convert it to a 0 to 100 measurement.

I had the function placed in my Main OB but the output of the function was linked to a marker tag not a DB. linked the output to a db and it works fine now.

thanks for the help