Hi,

This is very strange, as the values change it jump between the actual value and -100.
When the ramp stops at a value eg: 50, it would jump back to -100.

Another strange thing, this is AI_3 - adress 2, but i am changing AI_1 address 0?

Seems to be some address offset error. Maybe you should set ReadRegAddress to 1.

/Claes

Hi

I have added some screen shots, this is not making a lot of sense to me.

The values i am sending is incorrect and on the wrong addresses that it is send from.

Where do i chance ReadRegAddress ?

There is a lot more but only limited to 8 attachments.

Can someone give there opinion regarding this problem.

Hello PF,

For analog I/O with MODBUS protocol:

1. You have to take care of RawValRangeLow RawValRangeHigh (basically signed or not 16 bits integer) parameters which have to match with how it is set in your external PLC (Siemens ?)

2. You have to set also ActualValueRangeLow ActualValueRangeHigh parameters, they are in engineering units (32 bits floating numbers)(°C for example)

For instance, for a temperature sensor with -10->50°C range you can have these possibilities:

ActualValueRangeLow = -10
ActualValueRangeHigh = 50

As Unsigned int RawValRangeLow = 0 RawValRangeHigh = 65535 for full resolution
As Signed int RawValRangeLow = -32768 RawValRangeHigh = 32767 for full resolution

Or (case of Eurotherm SNCC)

As Signed int RawValRangeLow = -100 RawValRangeHigh = 5000 for better resolution (<= 32767)

So it will be the real value -10.00 <= ActualValue <= 50.00 °C

3 data address is sometimes given with an offset of +/-1 . It is the result of an historical commercial struggle between MODBUS (Gould MODICON) and JIBUS (MERLIN-GERIN).

If you have a data at the address 3 in your external Master device, it can be 2 or 3 or 4 in your slave device.

Begin to test with only one data and then more.

You can take a look to the tutorial video in documentation (Ben and Bruno).

I have made this one (Bruno's video) working with KEP interface with unsigned integer 12 bits raw values range (declared as 16 bits in Proview)

www.proview.se/video/ModbusTCP_4.mp4
www.proview.se/video/TramesModbus_5.mp4

Have a good day

/Bruno