Using Lookout to write a decimal point to an RTU in the field.

[Carp]

Is thier a way to send an lookout exp.(ex.1.56) to a known writable register on an RTU out in the field. I am using the modbus object. I plan to send this expression that I have created to a series of regs. in the field and pull the info to a readable screen to display the converted readings from lookout. I want to use lookout to handle the complexed math and send it to the registers. EX. The RTU sends raw data (40003)to lookout. I convert it in an expression and I want to send it to reg(40501) out in the field. Question # 2. I also need to see if I can use a portable laptop in the field that mirrors the main host and is updated when the host updates. This is for the same application above. This is a mobile RTU
if you will. But as you move around in a 70 mile area repeaters change.

[steven@ni]

The way to do this would be to use a series of radio modems connected up to the repeaters. Then, you would simply edit the modbus object properties to talk out of the serial port to the radio modem.

To receive and transmit data to specific registers, you would simply:

1) Open up your object explorer (Object -> Object Explorer)
2) Right Click on your modbus object and select edit connections
3) Set register 40501 = Expression

This should allow you to communicate with your RTU's and also send the values of the expression to the registers of the RTU's.

[Carp]

I am doing that already. I need to send a value of ex. 1.56 to that register, you cant send more than 2 values to a writable modbus register. I need to know the procedure for sending a value 1.56 to multiple registers to be pull out for a display. I know the process for the display. I just need to know how to do it in lookout.

[Khalid]

Hi,

It's not clear to me what exactly you mean by "you can't send two values to a register."

I am guessing you're trying to write a 32-bit floating point number. If this is the case, then here's how you would do it:

To write a 32-bit floating point value (decimal point), you will have to use the F registers. E.g., F40001. Lookout will then split the value into two 16-bit registers accoring to the IEEE floating point notation and write them in two consecutive registers.

Similarly, when you want Lookout to interpret two (consecutive) 16-bit registers in your PLC as a single 32-bit floating point number, you will use the F registers.

For a detailed description of all this please see the following two articles:

Detailed Descripti
ons of Lookout Accessing Floating Point Numbers/Registers in a Modbus PLC:
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/2de82ef20b2cc991862567f600432e33?OpenDocument

The Working Principle behind Reading Adjacent (32 Bit) D or F Registers of Modbus
http://digital.ni.com/public.nsf/websearch/4ef459f549fcc7028625660a000a7629?OpenDocument

I hope this is what you're looking for.

Regards,

Khalid

[Carp]

Thank you. I dont need to poll I need to write. I will look into it thanks.