Hikvision M-Series NVR Alarm Inputs without ground

[drmaven]

I have the DS-7732NI-M4/16P NVR, and I am trying to connect an AX Pro Relay (2 wires) to Alarm Input 1 so that I can enable/disable liveguard. However, i cannot see anywhere to plug the 2nd cable (ground). Previous NVRs had a GND terminal, which cannot be found in this M-series.

How would you do it?

 

[steved64]

That knurled+slotted knob at lower right of photo 1 is the ground, as is almost anything else attached to the metal case.

 

[drmaven]

Thanks for your reply. I am not sure I can connect it to this knob in order to close the circuit, since I think this is “earth ground”?

 

[alastairstevenson]

However, i cannot see anywhere to plug the 2nd cable (ground).

It's a pity the user manual doesn't have any info on the Alarm OUT connection wiring.

Each of the Alarm OUT channels has 2 pins, so they are either 'floating' outputs, or one of them is GND.
Do you have a multimeter you can test this with?

 

[drmaven]

It's a pity the user manual doesn't have any info on the Alarm OUT connection wiring.

Each of the Alarm OUT channels has 2 pins, so they are either 'floating' outputs, or one of them is GND.
Do you have a multimeter you can test this with?

I need to connect the ax pro relay to the alarm input. :/ the manual is truly awful on this.

 

[alastairstevenson]

Oops - for some reason I was thinking it was the Alarm OUT wiring that was needed.

For Alarm IN, the panel diagram shows the pillar at the bottom right of your image designated as GND, and there is just one pin per channel on the connectors.
Presumably the AX Pro relay is just a 'dry' contact.

 

[drmaven]

Oops - for some reason I was thinking it was the Alarm OUT wiring that was needed.

For Alarm IN, the panel diagram shows the pillar at the bottom right of your image designated as GND, and there is just one pin per channel on the connectors.
Presumably the AX Pro relay is just a 'dry' contact.

Excuse my ignorance (I am a doctor who has no idea about electrical wiring), if it's a dry contact how would you suggest that I connect the two relay outputs of the ax pro relay to the NVR? 1st cable -> Alarm Input 1, 2nd cable -> GND pillar?

Thank you for your time!

 

[alastairstevenson]

Sorry - a 'dry contact' is just an isolated relay contact pair, as opposed to an active type of contact that has a transistor or mosfet used as a switch to GND so not isolated.

would you suggest that I connect the two relay outputs of the ax pro relay to the NVR? 1st cable -> Alarm Input 1, 2nd cable -> GND pillar?

Yes, I believe that would work, on the assumption that the Alarm IN has what's known as an 'internal pullup'. Don't worry about what that means.

 

[steved64]

I chimed in here because I'm planning to upgrade to this specific
NVR and had studied its i/o as I have a few alarm-in devices
from doorbell relay and PIR.

The i/o panel is described well on the data sheet but not
in the manual. Signal ground and earth ground are often the
same thing. Many devices like this economize i/o connector space
by eliminating duplicate ground pins (or even all ground pins) and
expect you to deal with combining as needed to a shared ground.
That single post is ground for everything else that doesn't have one.

You can also think of it like an automobile electrical system; everything
that needs a negative can use the nearest body/chassis connection
so wiring needs are nearly cut in half.