RS-485 communication

[vikash23]

Hi,

I am trying to use PRESSURIZED WATER CIRCULATING TEMPERATURE CONTROL UNITS

Below is the link for the instrument and I have attached datasheet with this email.

https://www.evercoolltd.co.uk/single-product.php?pid=7.

On the datasheet the communication is mentioned as RS-485, 4-20mA, 0-10 volts

I would like to use RS-485.

Currently I have USB-RS485-WE. But regarding the RS-485 on the instrument there is no data how to communicate. I am looking for protocol.

Is it using MODBUS protocol. ? nothing is mentioned on the datasheet so what do i consider ?View attachment TC 140 Instruction & Maintenance Manual (English) (1).pdf

any example how to communicate using RS-485 is appreciated.

*Note : I am trying to use LabVIEW to communicate with my devices via RS-485.

View attachment TC 140 Instruction & Maintenance Manual (English) (1).pdf

 

[FvM]

Interface protocol is apparently not mentioned in the manual or datasheet. Why not email the manufacturer or ask your local dealer?

 

[vikash23]

Interface protocol is apparently not mentioned in the manual or datasheet. Why not email the manufacturer or ask your local dealer?

That's the first thing I did and the distributor of the product is not understanding what I am after.

I am new to serial communication and I just want to make myself clear If i have understood the working principle of the RS-485.

I had the same issue when using power supply from BK precision 9117.

They have mentioned only as RS-485. not what protocol to follow.

I emailed them and below is their response



Vikash,

RS-485 is only used to communicate between the units when they are connected in Master-Slave communication. Rs-232 is what you can use to communicate if you are using a computer to control the power supply.

Best regards




Can I also please know if RS-485 can communicate with out a protocol ?

Regards,
Vikash

 

[KlausST]

Hi,

Can I also please know if RS-485 can communicate with out a protocol ?

Theoretically. But it makes no sense.

It´s like two people speaking, but with different language.
Both people hear each other .. but they don´t understand each other.

Klaus

 

[vikash23]

So as per the reply mail from BK precision I wont be able to communicate with my power supply using RS-485 ?

I can use only RS-232? If using RS-232 then again what protocol I need to use ?

what data do i need to send to receive the message ?


OK let me come back to RS-485. I need to ask the manufacturer what protocol it works by ?

 

[FvM]

That's an outstanding ignorant answer to your question, I think. May be from a sales guy... They actually don't deserve to earn money with technical products.

You better email the UK manufacturer. Guess it's too late this week, but you can try.

In fact, any definition how to talk to the device can be considered as protocol. Most likely it either uses a popular industry standard protocol like MODBUS or ASCII (text commands with <CR><LF> termination). Most measurement instruments do the latter, I guess also the said BK device. Nevertheless the protocol needs specification.

- - - Updated - - -

The BK 9117 product page by the way refers to SCPI command language, that's almost a specification. https://en.wikipedia.org/wiki/Standard_Commands_for_Programmable_Instruments

 

[KlausST]

Hi,

If using RS-232 then again what protocol I need to use ?

It´s independent of RS232 or RS485....you have to speak the language of the device you wan t to talk with.

So if you want to communicate with the BK precision device you need to use it´s protocol.
If you want communicate with TC-140, then you need to use it´s protocol.

Maybe it uses some standard communication protocol .. but who knows? --> the manufacturer.
But even a standard protocol uses a standard "language". But you can´t be sure that both partners understand all commands.

It´s like with human beings. English is not my mother tongue. But I´ve learned some words ... so I can communicate a little here in this forum. But for sure I don´t understand all words.

Back to your devices:
Maybe the protocol uses ASCII signs, then - with a terminal software - you can read text. Maybe you understand the text, maybe not.
It could be MODBUS, but even then you need to understand the meaning of the transmitted bytes.
The same is with Profibus or other standard protocols.

In short: you need the manufacturer. He is (has) the "dictionary" that explains the transmitted bytes.

Klaus