G.E. MDS SD4 Diaganostics

Question

G.E. MDS SD4 Diaganostics

centaur821 (Electrical)

(OP)

4 Sep 11 22:31

I have two (2) GE MDS SD4 telemetry radios at a remote location with a master radio (also a GE MDS SD4) at a different location.  It's set up in a Master/Slave relationship.

The two radios are identical and I would like to know if it is possible to connect the COM2 ports (setup in RS-232 mode) together on each radio to be used for diagnostic purposes.  If one radio is being used as the primary radio to send data to the Master and the primary has a fault, is it possible to connect the COM2 ports of each radio (primary/backup) together where the primary radios alarm is output to the backup radio and the alarm status is then sent to the location of the Master radio by the Backup radio to notify personnel at the Master radio location that Primary radio has faulted?  Same thing if the backup radio goes into a fault, the primary radio would send the backup's status to the Master.

Now I believe the RS-232 pins must be configured to receive and send to the other radio's RS-232 COM2 port. Pin 6 is the Alarm Ouput signal (+5vdc is alarm condition & -5vdc is normal operating condition) and Pin 3 is an  RXD (received data) input.  Pin 5 is signal ground and would be grounded to a common point.  So could I take each radio's Pin 6 output and wire it to the Pin 3 input of the other radio and have it pickup the alarm condition of the opposite radio and forward it on to the Master radio location?

I hope I explained this well enough.  I am open to any other ideas that would work.

Thank you.

VEBill (Military) · Answer 1 · 2011-09-06 17:55:08

There are many different approaches to providing redundancy; it can be a science unto itself. Some approaches are better than others. Single points of failure, or single modes of failure (e.g. lightning), might easily take out both systems. E.g. External radio interference wouldn't be solved by switching in an alternate radio on the same frequency.

Switching to an alternate radio based on a fault signal from the failed radio would be a dangerous approach. What if the first radio fails such that the fault signal never arrives?

Also, if the backup radio has been sitting there for five years, what assurance is there that it'll work when required?

Do the system-level data and safety requirements allow you to run both radios in parallel on different channels? Or, do the system requirements allow you to switch back and forth on a regular basis so that when a link fails, the remaining 50% duty cycle can support the system?

Sorry that I can't help you with your specific question, but I hope this shows some high level considerations.

robertjo24 (Industrial) · Answer 2 · 2011-09-08 14:58:21

The SD series of radios is basically a marriage of the legacy licensed platform and the unlicensed IP platform (iNET). If you are using an SD4 as the master, it should have the Ethernet port enabled and available and can plug it into your network. If this is the case you can actively monitor the remotes through a standard network monitoring tool (like Solar Winds), and set up the radio system to send SNMP traps to a network monitoring and reporting system. If you have a group that monitors your network, they should have the monitoring tools already in place. GE MDS can provide the proper MIBS for the SNMP monitoring.

If you do not have this monitoring too set in place, GE MDS also markets a monitoring tool to monitor their radio systems.

To set up the system you would propose, there would need to be some back end process/mechanism inherent in the radio to report errors out the serial port. To my knowledge, there is not.

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G.E. MDS SD4 Diaganostics