RS485 network checker.

Hi,
I am wondering if someone knows of a device to check RS485/422 networks. Like there are for ethernet, that give us indication of the correct or incorrect connections and so on...

thanks;

Take a look at the Fluke Industrial Scopemeter, we have one, works well.

http://www.fluke.co.uk/comx/show_product.aspx?pid=38393&locale=uken&product=SCM

thanks. I'll be looking and praying that it get's into the budget for next year!

Yes, it's called a multimeter. Seriously RS-232 / 485 wiring is quite simple it's matching the baudrate, parity etc that takes the time.
A breakout box is also useful to identify the connections.
Regards
Roy

Roy,

What utility do you see in a multimeter for RS-485? I'm serious.

All multimeters average or integrate so when a line is active at any baud rate, so the value seen by the meter is some average value.

Do you know a trick for using a meter to determine which is A or B line (plus or minus) line? One Phoenix Contact division (wireless) uses the opposite convention of other divisions (automation) and it's a pain to not know whether A's are connected to A's and not B's. Mixing vendors on a 485 line produces the same headache.

Not too long ago a thread here was posted by the A-B tech support guy who used the Fluke meter to capture a waveform that was giving him headaches. I'll see if I can find it and link to it. It made me really want a handheld scope for those hair pullers.

Dan

See Ken Roach's post with screen shots from a Fluke 125 on this thread:

http://www.plctalk.net/qanda/showthread.php?t=35172&highlight=Fluke+scope

Dan

One of the guys I work with built a slick little box for testing rs-232 connections. He basically put a resistor and led across the ground and 5v terminals and then another resistor and led across the ground/rx and ground/tx wires. Soldered it all together and put it in a little plastic hobby box with DB9 connectors coming out of each side.

When you plug it in line with the connection the lights indicating proper grounding and 5vdc for each side of the connection come on. Then whenever data goes across the line the TX or RX led will come on.

If you are just trying to verify good electrical connections, you could probably expand on this idea for RS-422/RS-485 and do it with $20 worth of parts.

When the transmitter is idle you can quickly find the TX signals with a multimeter the + will indicate + in relation to ground -, - etc. the receive lines will both be at ground potential.

I also have a box I put together with a male and female DB-25 using a couple of 10 segment bar graphs 2 segments per line 1 for +, 1 for -, this is a big help (I never bothered making one for a DB-9 because it's easy with a multimeter.

Another trick is to use an old laptop to monitor the traffic. The laptop's RS-232 RX line you connect to the 485 (or 422) negative signal (ignore the positive).
Just take the shells off the interconnecting cable and touch the laptops ground and RX to the appropriate pins or bare a small section of wire.
You will see the data first of all as a bunch of garbage characters then by changing the laptops Baud rate etc you can quickly determine the correct settings.
The laptop will also act as a transmitter.
Try it out with a working system so you get familiar first.
Hope this helps