What Does Failed Null mean for a Loop?

[Davy Jones Locker]

Sent in my orginal Spectrum Xlt (Rainbow) XLT loop a few weeks ago.They replaced it with the newer style loop just says whites on it measured 9.5 inches.So i asume its a 950 loop.Went on to whites site to find the loop.It looks like the Blue Max 950 loop p/n 801 3217-1 pictured.So they replaced my old loop with a $ 149.95 dollar loop free of charge.My question is this .On the invoice it says old loop tested failed Null does anybody know what this means? Originally I sent loop in because it wasn.t working right in wet grass.

 

[GoGoGopher]

Can't beat that with a stick...nice deal on the new loop...Not sure, but I believe failed null, means failed to ground balance...I am probably wrong on this though...It could also mean it failed to impedence match with the detector...

 

[kraelity]

A coil is usually design with 2 coil loops 1-tx and 1-rx (transmitt- tx,receive- rx).
The 2 loops are place in such a way it creates a null (balance) until a piece of metal disrupts this null.
If one of the coils move (tx or rx) or the small circuit in the coil has a problem the null balance is gone.
The coil is dead.
White's is a great company, machines and service!!!!!
HH

 

[Dan-Pa.]

It seems the older whites 950 loop which is used on many of their units is prone to go out of tune and basically won't ground balance correctly. New 950 loop is just replacing a 950 loop that has been around for 20 years and although a different design seems to work well. Old loop was the same loop used on many different Whites units and all Whites did was put on a different sticker. Have to agree Whites sure provides excellent service after the sale with knowlegable reps and techs as over the years have dealth with them with excellent results..