Electrical arguement/question/ me showing my ignorance.

RhettMan

LawnSite Gold Member
Location
Texas
so a pgv will generally show on a resi system ~26 ohms. measured at the controller

so theres this system, with 9 zones, but zones 1, 2, 3, and MV (all geographically located in sequence in relation to other zones, (horseshoe around driveway)), show ~40 ohms (WHEN! measured with common connected to controller!), but/yet! ~26-28 when measured at controller but connected to nothing.

whats the deal.

had identical controller on hand, replaced ( i can now say...) like a dumby... same result.

Hope everyone is having a good dog days month, much love, carry on, hang in there.

5 bucks says jim or boots wins this one.
 

rlitman

LawnSite Silver Member
Location
Long Island
Let me see if I understand this correctly.
You're measuring resistance across a solenoid, at the controller end of the wire, and when the wire is connected to the common the resistance goes UP from when you measure at the same location with the wires disconnected?
 

1idejim

LawnSite Fanatic
so a pgv will generally show on a resi system ~26 ohms. measured at the controller

so theres this system, with 9 zones, but zones 1, 2, 3, and MV (all geographically located in sequence in relation to other zones, (horseshoe around driveway)), show ~40 ohms (WHEN! measured with common connected to controller!), but/yet! ~26-28 when measured at controller but connected to nothing.

whats the deal.

had identical controller on hand, replaced ( i can now say...) like a dumby... same result.

Hope everyone is having a good dog days month, much love, carry on, hang in there.

5 bucks says jim or boots wins this one.
It’s improbable you could receive a measurement value without continuity so i hazard to guess you’re measuring through the terminals when it’s connected to the controller and directly to the wires when it’s connected to nothing.

And since you’ve replaced the controller, the field wiring would be suspect.

Now if I’m translating Rhettanise correctly, the resistance values increase only when the controller is part of the circuit, when the controller isn’t part of the circuit the resistance values are normal.

I ask, when connected to the controller 1-2-3 & MV measure 40 ohms, do 4-5-6-7-8 & 9 also measure 40 ohms? Or do they measure 26-28 ohms?

I also ask, what brand controller and is it plug in or hard wired power source?

How is the controller grounded?

I’ve more questions after these are answered.
 

ArTurf

LawnSite Fanatic
Location
Ark
Just to clarify and not hurt Jim's feelings I declared Bootsy the winner since he answered 1st. Actually truth be know Rhettsy hurt my feelings by not including me in the possible winners list
 

sjwater

LawnSite Member
Location
San Jose, Ca
To measure the resistance of anything, the proper (by the book and kosher) method is NOT have it connected to anything at all. So, if a person wants to measure resistance of a Solenoid, then the "proper" way is to disconnect the darn thing from any wire and measure its resistance.

Connecting the wires to terminal of a clock (or anything else electronic) of any sort and measuring the resistance will 100% screw things up.

If the terminals of the clock are connected to a transistor (which most could be), then almost all of the multi-meters out there get messed up mainly because a transistor is a non-linear element (unlike a wire which is considered linear) and reading is NOT accurate at all.

Resistance of a wire increases with length, say a 1 feet wire is 1 ohm, then 100 feet of it would be around 100 ohms and that is linear or proportional. But a transistor is nothing like that because how it is made.

I would NOT trust any reading from a multi-meter if it is connected to a terminal of clock, not a good practice, that's all.

Hope this helps, I tried to geek it down, but I am not sure if I did it right!
 

1idejim

LawnSite Fanatic
To measure the resistance of anything, the proper (by the book and kosher) method is NOT have it connected to anything at all. So, if a person wants to measure resistance of a Solenoid, then the "proper" way is to disconnect the darn thing from any wire and measure its resistance.

Connecting the wires to terminal of a clock (or anything else electronic) of any sort and measuring the resistance will 100% screw things up.

If the terminals of the clock are connected to a transistor (which most could be), then almost all of the multi-meters out there get messed up mainly because a transistor is a non-linear element (unlike a wire which is considered linear) and reading is NOT accurate at all.

Resistance of a wire increases with length, say a 1 feet wire is 1 ohm, then 100 feet of it would be around 100 ohms and that is linear or proportional. But a transistor is nothing like that because how it is made.

I would NOT trust any reading from a multi-meter if it is connected to a terminal of clock, not a good practice, that's all.

Hope this helps, I tried to geek it down, but I am not sure if I did it right!
If you measure between any 2 terminals on a controller you receive a value equal to infinity.

If you connect a solenoid between any 2 terminals you’ll receive a value equal to the resistance of the solenoid.

If you add a 100’ of wire to the scenario (let’s say 18ga at 6.380 ohms per 1,000’) you’re only adding 0.638 ohms to the equation. So, with a solenoid measuring 27 ohms and you add 0.638 ohms, maybe factor in some resistance created by the splice (?) you’re seeing something like 27/28 ohms? Which shouldn’t matter much since the industry considers 20 - 60 ohms a goo
 

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