Data transfer rate control

[M_Atif]

Hi,

I have two questions.

Question No. 1

Some time i cannot acquire accurate Analog data from my lookout version 5.0 process, i am using momemtum PLC and i set the raw units from 0 to 4095 (which is provided by manufacturer). and set the value of engineering units from 0 to 400, as 400 is the maximum value which can be acquired from the sensor/field device.

Question No. 2

How to control data transfer rate.

I am using mostly digital IOs, but about 30 Analog inputs are in use. when i check the transfer rate from the LAN Adapter, it is transfer about 1000 byter in on tranaction. at the same time for other process where my Digital IOs are in about 500, but the process data transfer about 50 to 70 bytes per transition. Please tell me how i can control this trasfer rate.

Thanks

Atif Sarfraz

[Khalid]

Atif,

What Object are you using?  What kind of discrepancy are you seeing with your values?  What's the raw alues, if you use no scaling? 

As for the transfer rate, the main thing you have control over is the Poll Rate.  This decides when Lookout polls the device/PLC for values.  Outputs however, in most PLC Objects, are written at once.  Again depending on the PLC, reads/write may be blocked (grouped) together if the registers are contiguous or close enough. 

-Khalid

[M_Atif]

Thanks for reply.

a. I am using Modbus object to communicate and using Network option module of 100 mb/second. and simple display object to show the values.  Raw units minimum=0 Maximum-4095. Engg units minimum=0  and maximum is 400. (Which is the maximum value for thermocouple).

b. As i told you that i have no problem with DOs,problem is with Analog Inputs, because they are changing rapidly/continuously becuase of their normal behavooiur. Please tell me the how  change/increase of  poll rate is efficient, when i increase the poll rate it will also slow down the feedback of Digital IOs too and this i cannot affored, because my process is dependent on the feedback. Please tell me can DEVIATION can help me to control the transfer rate (which is for data logging trigger).

Thanks.

Atif

Bahrain

[Khalid]

Atif,

a.  Modbus Object in Lookout, as you may know, has several datamembers for interpreting the same registers.  Depending on which ones you use, the values will be interpreted differently.  For example, if you use the F40001 instead of just 40001, the values are interpreted as floating piont numers (and actually use two adjacent registers). 

Then there's the issue of endian-ness.  You will see this, and other, options under the Advanced settings of the Modbus Object. 

Does the PLC have the raw or the Engineering values in its registers?  What registers are these?  Are they to be interpreted as floating point numbers? 

b.  If you want to poll some items in the PLC at a different rate than others, one option is to create multiple objects -- with different poll rates for each.  Lookout allows you to have multiple objects with the same comm settings, but different poll rates. 

Hope this helps.

-Khalid