Two sensors (with resistors) on one zone

Hey all I have a question:
 
I want to install two sensors (they each have an integrated resistor) on one zone.  The problem also is that the zones are NC not NO.  Is there any "smart" way to do these?  Obviously if one didn't have the resistor I could wire them in series (each one has home run wiring) and then things would work properly I believe.  Any thoughts?
 
Thanks so much!
 
Neil
 

What's the resistor value?
 
The easiest I can think of is a TTL relay with a minimal pull in voltage value and then use that to trip the panel zone.

Is the standard HAI value (1k?) I don't know.  I am looking at replacing half the sensors without the built in resistor.  Adding a resistor could get costly and not really worth it?  The panel will already be a hot mess without a relay....
 
Thanks,
 
Neil

For normally open, a 1K resistor placed in parallel with sensors in series could be used (sensors in series in parallel to the resistor).  
 
A relay is a excellent idea too and could be a better thing if you wanted to trigger each sensor in series while on the same zone.  A small relay won't generate much in the way of heat (if that's what you meant by hot mess) but a resistor will get the job done too plus resistors are cheap at a nickel to 15¢ each!
 
The only difference between NO and NC sensors is series resistor or parallel resistor described in more detail in the install manual.

You haven't said what the resistance value of each sensor is. The M1 considers any voltage from 4.0 to 8.8 on each loop as a ready state so there is a fairly wide range of resistance that will work properly. Lookj at page 9 of the installation manual.
 
Mike.

Its a 1k resistor going on an Omnipro II. Thanks.  I wasn't concerned about the temperature just the mess inside the alarm panel cabinet...
 
Thanks!
 
Neil

I'm sorry but I thought that we were talking about an Elk system. I found this thread through a search and didn't notice that we are in the Hai forum. Duh!
 
I did a little search and yes it loks like the EOL resistor on the HAI zone is 1k ohm.
 
Mike.

So back to your question, if you are planning to combine two sensors on one zone, the 1K each together for two would be too much resistance.  The only solution would be to dig into one of them and bypass the resistor so one would have a resistor and the other didn't, then put them in series.  They could have their own zone, but that would defeat what you are trying to do.

Two 1K ohm resistors in series are 2K ohms.
 
If you add a 2K resistor in parallel at the panel (brings the total NC resistance down to 1K), would that work?

sda said:

Two 1K ohm resistors in series are 2K ohms.
 
If you add a 2K resistor in parallel at the panel (brings the total NC resistance down to 1K), would that work?

Click to expand...

No.  That would work fine when the zones are secure, but when one opens the panel would see 2K resistance, which would report as a wiring fault.  The only acceptable total resistances are under about 150 ohms, around 1000 ohms, and very high resistance.  One between those levels will report as a fault. 

sda said:

Two 1K ohm resistors in series are 2K ohms.
 
If you add a 2K resistor in parallel at the panel (brings the total NC resistance down to 1K), would that work?

Click to expand...

If I was to put a resistor in parallel to reduce the resistance I would do it at one of the two sensors but I would prefer to remove the resistance from one of the sensors if possible.
 
Mike.
 
Mike.

sda said:

Two 1K ohm resistors in series are 2K ohms.
 
If you add a 2K resistor in parallel at the panel (brings the total NC resistance down to 1K), would that work?

Click to expand...

"electrically" and academically, yes, but in the overall scheme of a panel that would report opens, shorts and high resistance faults, it's not going to work.
 
The easy answer is to correct the resistors in the field. If that isn't an option, a TTL relay (IE: Elk 924) with a low enough voltage tolerance to suck in the coil would be the ideal solution (albeit at the loss of true supervision).

I ordered non resistor sensors and I will just use one resistor and one without.  That should solve my problem I believe. There was no good way to make it work with two resistors and I didn't want to double up the zones for two windows or a slider with two sides.
 
Thanks!
 
Neil