Rs485

kra101 · May 10, 2006

Dear all,

I have a project where I have SLC 5/04 and more than 100 numbers of RH transmitters 4-20mA. I can connect them through NI8 modules. I found a brand called “testo”, which can be networked by RS485. Now my question is can I connect this network to SLC and if it is possible, do I need to use massage instruction to read the data?

Please advice.

Thanks in advance.

KRA

rohan tandon · May 15, 2006

Could you post more details about what you are trying to achieve? What product of testo are you interested in? They do have several kinds..

Are you trying to connect the analog inputs to the 'testo' and then import the data to SLC?

Tom Jenkins · May 15, 2006

There are Basic co-processors available for the SLC from third party suppliers like Spectrum. That might be the easiest way to poll the transmitters and de-code the responses.

rods87 · May 15, 2006

I have used modules by ProSoft. There are limits to the number of RS485 devices that can be connected to the ports, I think 16 to each of the two ports. They aren't cheap, maybe $1100, but should be much more cost effective than four times as many NI8 modules.

Bill McEwan · May 15, 2006

What update time do you require for the analog inputs?

For applications with large numbers of analog inputs we use a multiplexer to connect 16 channels into a single channel of the SLC input module. This works very well if you don't need really fast update times.

kra101 · May 16, 2006

Dear all, Thank you very much for the answers.

Rohan,

I am trying to use “testo” humidity transmitters, for example I have 30 transmitters, which can be networked by RS485. If it is possible to connect this network and get data to SLC, I can save NI8 modules and cabling.

Bill McEwan,

Update time is not very critical. Can you please post the details?

Tom & Rods87,

I will contact Spectrum and ProSoft.

Regards,

KRA

ckchew666 · May 16, 2006

Bill McEwan said:
What update time do you require for the analog inputs?

For applications with large numbers of analog inputs we use a multiplexer to connect 16 channels into a single channel of the SLC input module. This works very well if you don't need really fast update times.

Hi,

The multiplexer you are talking about is a device to accept 16 Analog Input (from RH Transmitter) and has one analog output connecting to the SLC NI8 channel, so the multiplexer will scan each channel and update the value to the NI8, am I right?

Bill McEwan · May 18, 2006

Yes that is correct.
The multiplexer has digital inputs to step it through the channels and to reset to the first channel. These are what we use http://www.intech.co.nz/products/remotestations/remotestations.html

I'm sure others make a similar product. This company is represented in the US.

kra101 · May 20, 2006

Bill McEwan,

It is very interesting, thank you very much.

Regards,
KRA

Rs485

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