NB250 dry contact sensors disconnects and connects again

DCIM_Support · ‎2020-07-04

Hello

I replaced a clients NB200 with a NB250 2 months ago and connected all the old sensors on the same ports as the old Netbotz unit including two "Dry contact" sensors connected with the original NBES0304 cables. I added a few temperature sensors and wireless sensors as well.

A week ago I started to get "Dry contact sensor disconnected" alarms and a few seconds later the alarm cleared again. After a few minutes it repeats itself.

This happens on both of the dry contact sensor inputs so I can rule out an hardware error on the sensor cable itself or the device connected to the cables.

09/05/2018 15:56:57 Device NB: Sensor connected for 'XXX' at 'XXX'.

09/05/2018 15:56:54 Device NB: Sensor Disconnected for 'XXX' at 'XXX'.

the state of the sensor (open/closed) does not change, it just disconnects and disappears from the sensor list and appears a few seconds later.

So why does this occur?

The rj45 contacts are plugged in as they should be in the sensor ports.

I have done a soft restart of the NB250 but that did nothing.

Is this a firmware related error? the NB250 runs the latest 6,5,6 version and the wireless sensors connected runs the latest release as well.

The site is an unmanned site so there is no option to go to the site and do a hard reset every time this starts to occur.

DCIM_Support · ‎2020-07-04

Hi Adam lindberg, thanks for posting!

Let's hope you find your answer here.

Thanks,

Stine

DCIM_Support · ‎2020-07-04

Not sure if this is related, as this was a few years ago, but the symptoms sound similar. I had a NB200 that was doing similar things when using dry contact sensor. But only if I have more than 3 dry contact sensors connected. This happened on a replacement NB200 too.

I was informed at the time that this is a firmware issue, and to cut a long story short I ended up connecting a NB Pod 150 to the A-Link of the NB200 and connecting all the dry contact sensors to that.. The system has been running for a good few years since with no issues (as far as I know).

I suspect that the NB250 shares some firmware from the NB200 as there was a firmware update recently on the NB250 that addressed one of the bugs of the old NB200. Maybe this dry contact issue is still there too?

DCIM_Support · ‎2020-07-04

Hello

Yeah That might be firmware related, but that solution is not an option for this client I'm afraid. They have about 60 NB200 that will be replaced with NB250 units and to buy 60 NB150 pods just to get the dry contacts to work is not an acceptable solution.

I have a suspicion it might have something to do with the Sensor identification resistor in the old NBES0304 cable. my cables are about 10 years old and Schneider might have raised the threshold for the identification value in the new firmware so the older cables might just be on the edge of the accepted identification threshold.

But its a really big task to change all the sensor cables if that's the case, I don't have a new NBES0304 cable to measure the values in so I cant confirm my suspicion, but it might explain why the sensor identification connects/disconnects at random intervals, the next values under "dry contact" is not used for the moment in schneiders identification list so a "dry contact" sensor with a lower than specified resistor value is not identified at all and does not show up as a connected sensor.

the easy solution to this problem would be to lower the threshold in the firmware a notch I think, It would be nice to get an official response to this question.

DCIM_Support · ‎2020-07-04

Another thing i remember was that some old Netbotz units had to small psu's inside so if there were to many sensors on the pod the voltage was going into undervoltage and the pod was nomore aible to see the sensors.

Maybe someone from Netbotz R&D can bring some light into the dark!

DCIM_Support · ‎2020-07-04

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