Astec Sensor Testing

kelbal

Hi guys,
I've seen some of you mention in other threads how to detect which sensor(s) are causing a fault in a certain zone of an astec system (63DV), here for example, http://www.boards.ie/vbulletin/showthread.php?t=2056655452. I just wanted to get a little bit more precise info on the steps involved, thought a new thread would be best.
So, I disconnect the 2 wires on the top strip of the main system circuit board for the zone in question. Then these 2 wires are hooked up to the multimeter, which is set to ohms. To be able to test I'll need to extend the 2 disconnected wires via a long lead so I can see the results as I'm testing each sensor. When I start, the resistance should be low enough, couple of ohms. When I tap a sensor, if its a good one it should jump by a couple of ohms and quickly drop back to original value. What would a dodgy one do?
I saw in other threads to remove the End of line resistor from the sensor on the loop. I've opened up all the sensors and don't see any resistors at all, however there is a resistor added on to one of the wires going into the main circuit board for the zone in question. Guess this counts as the EOL resistor? Will take it out of the equation.
Does this all sound OK? Can someone just confirm what happens to the resistance readout on the multimeter when I encounter a dodgy sensor?

thanks in advance

KoolKid

Take the resistor out at the panel . The reading will be in ohms based on the length of the run. A good sensor will always return to near enough the same value. A faulty sensor will stick up a few ohms or more. It may also be the case that the reading starts high & drops when you tap a sensor.

kelbal

Thanks Koolkid. Looking at it now. The whole setup seems to settle out at 14 ohms. On one or two of the sensors, when I give them a whack, the resistance jumps and then might settle back at 19, another whack and it settles back at 16, another and it might go back to the 14. Is that the sign of a dodgy one? Not sure what the margin of error is here - should it be going back to pretty much the same value (or with .2 or .3 of an ohm?)

thanks

KoolKid

Yeah anything sticking up a couple of ohms or more I'd be changing on Astec sensors.

kelbal

thanks, think I've identified 2 where this is happening.

With 2 other sensors, they really need a good whack to identify any change in resistance at all. Do you reckon these ones could be setting off the alarm by mistake at all - or have they just lost some sensitivity and are not as effective?

KoolKid

Have you got the meter set at 200 ohms?
Are they all sensors?

kelbal

KoolKid wrote: »

Have you got the meter set at 200 ohms?
Are they all sensors?

yep, set to 200, all are normal vibration sensors. The resistance does jump and then settle back to 14 ohms - its just needs a right old whack to get it to register. Wondering whether to bother changing those ones.

KoolKid

Hard to know without seeing it. They should all react the same.

kelbal

OK, will just give it a go with the definitely dodgy ones and see how it goes.

thanks for your time

Rayzor1

Hi, Just wondering if someone here could help me please.
I too have an astec (63DV)alarm installed.Every now and then I get a false alarm on zone 3 saying contact entry.
I think it happens mainly when there is a temperature difference suddenly but not 100%.
I've disconnected zone 3 at the board and took out the end of line resistor and joined the wires at that sensor to complete the loop.when I test the resistance on multimeter on 200 ohms I get 1...when I increase multimeter to 2k I get 1.524...
My loops have 9 sensors on them and there's a long run of wire to them.I tested zone 1 to see what that gave me and it says 27ohms on 200 on multimeter.I've checked all the connections on the sensors and all are sound.I'm wondering now could it be a faulty sensor or is it a bad wire.any help would be much appreciated.thanks.

KoolKid

9 sensors is a lot for one zone. Have you tested all the resistors on the full loop at 27 ohms?
Tap each sensor 10-20 times if necessary. I would be confident you will find one, if not more , faulty.
Also when you find one faulty remove it from the loop and close off the cables.

Rayzor1

thks for your reply Koolkid.I have 6 zones with 9 on each zone...I have sliding sash windows and patio doors and have contact sensors on each window and door so I know if one is left open or not.Its been working fine during the winter but as the weather gets warmer it seems to trigger false alarms.I noticed the same last yr also.I havn't tested any resistors.I just undone the resistor and and tied the 2 wires together to complete loop and tested the resistance of the zone.I done a continuity test on zone 1 at the panel and it passed but the zone 3 didnt pass so i'm checking the wiring now from sensor to sensor in case of bad wire.If wiring is fine would it be a dodgey sensor causing the resistance problem?? or would it be a bad resistor...I think from a previous post tapping the sensor and checking how the resistance changes will find if the sensors are bad but how can I check a resistor is working properly??appreciate your help...

KoolKid

More than likely it's any of the devices that show up when you test the resistance.
Replace any you find. If there are contacts on the sensors you will need to wire 680ohm resistors across each contact if you are replacing the device as Astec devices are no longer available.
The resistor is not likely to be the problem. If you want to test it put a meter across it set at 2k .

Rayzor1

Thks for the info Koolkid...I undone all the wires from the sensor/contacts and redone and now am getting 24ohms.
I tested the resistance when opening windows and doors and banged the sensors about 10times each and the resistance went to 1 and then back to about 24.5ish...tested the resistors and getting 1.5k so they are ok.The last false alarm I got was on the zone 3 back door which was a contact entry.seems ok when tested opening and closing...any ideas what may cause that?? I put everything back together and will see how it goes from here on.

KoolKid

Add half the sensors back on and work forwards or backwards from there with a process of elimination.