false alarm

[vernerbongo2]

new installation, I put a pir in a sun lounge which has glass all around.
The pir does face away from the glass.(I know I probably shouldn't of put one there in the first place)
I get false alarms all the time in this zone only.(mostly at night, nearly every day)
I have just checked the wiring and terminals and changed the pir today to see if this solves the problem. (so I dont know yet)
put the zone on a soak test.
Can anyone tell me how to check the loop resistance of a zone, preferably with a few illustrations. As it could be that the cable is damaged!

 

[breezer]

I know I probably shouldn't of put one there in the first place

doesnt help does it.


you should check the resistance of the cable

also check the voltage at the detector

check the connections are good and tight

 

[imigix]

new installation, I put a pir in a sun lounge which has glass all around.
The pir does face away from the glass.(I know I probably shouldn't of put one there in the first place)
I get false alarms all the time in this zone only.(mostly at night, nearly every day)
I have just checked the wiring and terminals and changed the pir today to see if this solves the problem. (so I dont know yet)
put the zone on a soak test.
Can anyone tell me how to check the loop resistance of a zone, preferably with a few illustrations. As it could be that the cable is damaged!

movement detectors must be firmly mounted and not subject to movement themselves.

you have not stated what your cons. is made of but if it is upvc and your detector is mounted on it as the frame expands or contracts false alarms will happen.

i use a 360 degree Dual Tech in mine ( Scantronic 450 ) mounted on the house structure which forms an arch as one passes through from the dwelling into the cons.

in day time the sun must not shine or be reflected into the lens even if it has a white filter lens

my cons faces due south and i have no problems.

to check loop resistance i would suggest the following you need a muli meter set it on the low resistance range.

cut yourself some alarm cable to around the same length as you have running from your panel to your cons.

at one end join two conductors together at the other end measure the resistance and note the reading

then repeat this with your cons. cable and compare results.

 

[breezer]

i would sugget comparing the reading on a piece of cable the same length is a waste of cable and time.

just meter the existing cable and see what the resistance is

it is also worth noting some detectors have an internal resistor to protect the alarm contacts (not high, some are 33 ohnms)

 

[imigix]

i would sugget comparing the reading on a piece of cable the same length is a waste of cable and time.

just meter the existing cable and see what the resistance is

it is also worth noting some detectors have an internal resistor to protect the alarm contacts (not high, some are 33 ohnms)

Breezer you are missing my point as Vernerbongo 2 has asked the question about how to check loop resistance i make the assumption he is a enthusiastic amatuer and not a professional.

he could just measure the cable to the cons. but how would he know if the resistance was correct without a referance value.

you are correct in your statement regarding the internal resistor but i said that he joined the cable together at one end and measured from the other.

perhaps to be fair i should have said that he disconnect the pir and the panel beforehand.

 

[Deryck Tintagel]

he could just measure the cable to the cons. but how would he know if the resistance was correct without a referance value.

The alarm cable should have a resistance of about 92mOhms (0.092Ohms) per metre.

Disconnect the zone wiring at the PIR and short together. Remove the zone wiring at the panel and measure the resistance of the zone wiring. Estimate the length of the cable run and multiply by the resistance per metre and double it. Compare with the meter reading.

Check the meter reading with the probes shorted - not all give zero reading!

 

[imigix]

he could just measure the cable to the cons. but how would he know if the resistance was correct without a referance value.

The alarm cable should have a resistance of about 92mOhms (0.092Ohms) per metre.

Disconnect the zone wiring at the PIR and short together. Remove the zone wiring at the panel and measure the resistance of the zone wiring. Estimate the length of the cable run and multiply by the resistance per metre and double it. Compare with the meter reading.

Check the meter reading with the probes shorted - not all give zero reading!

yes Deryck Tintagel your suggestion is perfectly correct i was trying to make it as simple as poss.

 

[vernerbongo2]

I haven't heard of any faults on the zone since my first post, hopefully it was just a bad conection!
I will try the loop test when I get a chance, just one thing if thats the simple way to do a test whats the more complicated way
Will a basic meter do the job
Thanks to everyones input

by the way I did check the voltage & it was about 13.8 volts

 

[breezer]

I haven't heard of any faults on the zone since my first post, hopefully it was just a bad conection!

looks to me like there is no sunshine.

as I first mentioned sunshine and PIR's do not go well, wait untill spring.

the voltage you mention 13.8 is good to have at the detector although if its 13.8 at the far end whats it like at the panel?

 

[vernerbongo2]

I haven't heard of any faults on the zone since my first post, hopefully it was just a bad conection!

looks to me like there is no sunshine.

as I first mentioned sunshine and PIR's do not go well, wait untill spring.

the voltage you mention 13.8 is good to have at the detector although if its 13.8 at the far end whats it like at the panel?

can't remember exactly the voltage at the panel but it is around the same figure!
Bye the way what about a dual tec pir would that work better ? surely the sun wouldn't come in to play then?
Thanks

 

[breezer]

clicky

 

[davet0_uk]

I reckon dual tec pair is the way forward... as you say sunshine, rapidly changing heat and straight PIRs don't mix too well.

The other thing you could try is ...

see if the PIR has a pulse count jumper. If it does, put the pulse count jumper on as higher number as they have and see if you still get false alarms. This should de-sensitize the PIR from a single trigger. (i.e. it will take a multiple trigger of the sensor for it to trigger the panel)

But really in this sort of environment dual tech is the way forward to be certain..

 

[vernerbongo2]

see if the PIR has a pulse count jumper.
..

set at normal, no lower setting and I think double knock at the panel defeats the object.
dual tec if I have any more problems (although client doesn't like the sound of microwaves on him and the kids )

 

[breezer]

(although client doesn't like the sound of microwaves on him and the kids )

tell hin life is tough.

microwaves are also used for / on

opening doors as you walk towards them

trafiic lights

pelican crossings

 

[vernerbongo2]

he could just measure the cable to the cons. but how would he know if the resistance was correct without a referance value.

The alarm cable should have a resistance of about 92mOhms (0.092Ohms) per metre.

Disconnect the zone wiring at the PIR and short together. Remove the zone wiring at the panel and measure the resistance of the zone wiring. Estimate the length of the cable run and multiply by the resistance per metre and double it. Compare with the meter reading.

Check the meter reading with the probes shorted - not all give zero reading!

Forgot to say, I tried this theory out after this topic.
I'm not sure how my meter works, set meter to the lowest setting (2k).
My cable reading was .027 and the theorys was 2.76, if I put my meter up to the next position (20k) I get .2 reading.
Were am I going wrong? when the meter probes are shorted together the reading is 1 is this my problem?