Reading RTD values...can anyone explain this?

Mas01

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The values in blue are the live, monitored values and are all consistent with a cold day where our rig has.not been running for a while. So it looks like the integer values, you just divide them by 10 to get actual values.

Does each rung represent an individual channel on the card?
Can't understand why there's a need to subtract decimal value 6 or decimal 7 from the G-words(?). Mystery!

IMG_20201124_164035.jpg
 
It seems that these K constants are an offset because the programmer believed that the read temperatures were between 5 and 8 tenths higher than the real ones.
 
Not exactly, the Ux\Gx are the (U) address (G) buffer memory and the K is the word number so in this case it is reading buffer memories 11-18 (assuming 8 channels) in other words the digital value of the A/D conversion this is obviously the Temperature probes and is in decimal format with an implied one decimal place so converting to a float then dividing by 10 will give you xx.x Deg C, often there is no need to convert to a float as it can be used for calculations as a decimal and many HMI's can use implied decimal places so 100 on the HMI will display as 10.0.
Edit: May seem confusing but what appears to be reading similar addresses is that there are a number of RAW digital values, these are direct conversion, filtered conversion etc.
There are other ways to read values from the buffer memory using the From instruction for example [FROM K11 K8 D10] but this fetches 8 words from address 11 to 18 and stores them in D10-D17 so only one call to fetch all 8 channels.
 
Last edited:
Not exactly, the Ux\Gx are the (U) address (G) buffer memory and the K is the word number so in this case it is reading buffer memories 11-18 (assuming 8 channels) in other words the digital value of the A/D conversion this is obviously the Temperature probes and is in decimal format with an implied one decimal place so converting to a float then dividing by 10 will give you xx.x Deg C, often there is no need to convert to a float as it can be used for calculations as a decimal and many HMI's can use implied decimal places so 100 on the HMI will display as 10.0.
Edit: May seem confusing but what appears to be reading similar addresses is that there are a number of RAW digital values, these are direct conversion, filtered conversion etc.
There are other ways to read values from the buffer memory using the From instruction for example [FROM K11 K8 D10] but this fetches 8 words from address 11 to 18 and stores them in D10-D17 so only one call to fetch all 8 channels.

Thanks for this.
Question: how can you tell the K are word numbers and not decimal integers? From the code it looks like a subtraction command. I don't understand that.
 
U0\G11 to U0\G18 are 16 bit registers on the Anolog Input module that are transfered after integer subtraction to D11 to D18 that are PLC 16bit registers.

K constant is an integer decimal constant, H is an integer hexadecimal constant

To know the exact meaning of U0\Gn registers you need to consult the Analog Input module manual.
 
U0\G11 to U0\G18 are 16 bit registers on the Anolog Input module that are transfered after integer subtraction to D11 to D18 that are PLC 16bit registers.

K constant is an integer decimal constant, H is an integer hexadecimal constant

To know the exact meaning of U0\Gn registers you need to consult the Analog Input module manual.
H? H doesn't come into this question.
Were you trying to reply to my other thread?
 
Oh Dear...... forget my last post It's my bad on this one, I was actually doing a bit of code for someone else at the time using the TO/FROM instructions & got my nickers in a twist, and of course probably with your other post. They are subtracting constants from the values in decimal, although it is only 0.5-0.8 Deg C.
The problem is I was thinking about the FROM instruction where two constants refer to the Buffer address & the number to fetch forgetting the Ux\Gx notation of using the buffers directly in the code.
 

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