Loop readings

I have a Normally Open zone that has a loop value of 137 when secure; However, it has recently started randomly dropping to 136 from time to time which puts in a Not Ready state.  I have tried replacing the limit switches and the resistors on the zone in case they were faulty, and checked the wiring, but I still get the same result with a new switch and resistors. 
 
Is there a simple way that I can make the normal secure loop value 147 so that these small fluctuations get ignored? 
 

Use a multi-meter
Whats the measured value of the resistor?
What's the measured resistance of the entire loop?

How long is the wiring run?
What type of connections did you use (wire nuts, beanies, other)?
What type of sensor are you using?
Check the wire terminations at the board to make sure the wire did not get nicked or become fragile from metal fatigue and is making intermittent contact.

I found this with a search of CCT, maybe it will help:
 
http://cocoontech.com/forums/topic/22380-loops-values-for-hai-omnipro-ii/?hl=%2Bhai+%2Bloop+%2Bresistance#entry182857
 
Mike.

You could use a slightly higher resistor to adjust it, but that would be a last resort. Try to find the cause of the problem.

I have had a poor connection cause this.  When I removed the sensor to inspect the wire came out of the connector.
 
I also had a zone that daisy chained several sensors and I inadvertently added two EOLs in series.  :blink:

From the message above I think that the problem is exactly that the zones are cross-linked but I'm not clear exactly how, or how to avoid this. Here is how I think the circuit is wired. 
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A NO zone with an EOL is not an open circuit, it is a continuous loop through the EOL in the SECURE state.
In the NOT READY state the sensor bridges the EOL and it becomes a continuous loop with near 0 resistance, but still a complete circuit.
A NO zone conducts in both states.
 
A NC zone with EOL is also a continuous loop through the EOL in the SECURE state.
In the NOT READY state it becomes an open circuit when the sensor opens the loop.
A NC zone conducts only in the SECURE state.
 
In either case, regardless of the number of sensors on the loop, or their type NO/NC or mixed, you can only have one EOL per zone.
You also can't share commons between zones.
 
 
Do you have both sets of contacts on a single zone, or is each on a separate zone?
That 3 position switch, is there two sets of terminals, or do the zones share a common?

You can share a common between zones. You can also share the negative with the zones on powered loops. Very common for those "in the know" to eliminate a splice or split a zone where no other choice exists.

Desert_AIP said:

In either case, regardless of the number of sensors on the loop, or their type NO/NC or mixed, you can only have one EOL per zone.
You also can't share commons between zones.

Click to expand...

How do you share a common on an Omni Pro II board?
I tried to wire a 3 wire detector that has two states and dry contact outputs with a shared common and had to rewire it through independent relays to separate the contacts.
When I wired it to two zones the electric path would always jump across run back along the common through the internal resistor (I believe) of the other zone.
It was one big loop.
So I never got the indication where one zone would open and the other would close.
 
I don't see Omni listed in your User ID info, is the Omni wired differently internally?

Location of the resistor vs. the common. You put the resistor on the high side of the zone, not the common.
 
Omni is no different than most security panels out there. Data ports are different, but protective zones are not isolated.

Very few panels available in NA have isolated negatives or commons and those are generally "foreign" designed units anyways (IE: some Bosch, DSC, etc.)
 
More details on your 3 wire unit and states it's monitoring (NO, NC, etc?) if you're using a 4-20 type unit or digital type detection, that would be a variable

I don't understand how that is possible.
The zone is a continuous loop, there is no "+" side for the resistor.
The loop goes from the "+" through the resistor to the "-".
So one end is on the "+" and the other is on the "-".
 
If you jumper the two "-" poles of adjacent zones, then you connect the two loops together.
The zones also have internal resistors, so two jumpered loops like that will pass current through the internal resistor to the "+" pole, even if the loop of the itself is broken.
 
That was the problem I was having, it never saw any change in either zone.
 
I tried every combination I could think of, even tried blocking diodes.
But the jumpered "-" poles defeated every attempt.

Just discovered a loose connection in the motor circuit. oops. thanks all.

Aren't all the zone negatives on the OMNI connected together to ground?  The zone + is a constant current source with a built-in voltmeter, so in effect each zone is an ohmmeter but zone's loop value is the voltage across zone terminals.
 
I don't know the actual values, this is an example only, but lets say the OMNI zone has a constant current of 2.5 ma. All zones use the same current, with the possible exception of fire zones.  So you put the EOL resistor across the zone. 1K resistor with a 2.5ma current yields a voltage of 2.5V. The OMNI measure the VOLTAGE across a zone terminal and converts this to a loop value using an 8-bit using an analog to digital converter. That loop value is what tells the OMNI not ready, secure or fault. So EVERY zone consumes power when secure or shorted but not open.
 
It isn't very smart to share a zone common for multiple zones, because wire resistance of the common could lead to some strange results.  As zones open and close the total current carried on this common wire will change, and this could lead to the zone voltmeter having incorrect results. Each zone should have its own two wires. I'm sure there are exceptions depending on length but do it at your own risk. 
 
At least that is what I've seen on the OMNI.

Each zone has its own two wires - pls see my previous post

cestor said:

Each zone has its own two wires - pls see my previous post

Click to expand...

What you are doing seems fine.  Just disconnect everything from one zone, and simply put the EOL resistor across it. What does the loop read?  It should be around 127-129. 137 is too high. You have either a wiring problem, or a bad or wrong EOL resistor.