Minelab X-Terra 70 Uživatelský manuál stáhnout pdf (Strana 2)

52 | The Searcher July 2006

In the field

The first field was; you guessed it, the

pasture field. This time though it was

deliberate as I know what to expect in

terms of finds and it would be a perfect

place to compare the two detecting modes.

I began in the middle of the field with

the Sensitivity at 25, and Discrimination set

to reject from -8 to -2. There are three ways

to Ground Balance; Auto, Manual or Track.

Track is by far the easiest method, simply

press Track and the detector will constantly

track the ground. Manual Ground Balance

will generally offer a slight depth

improvement. To use this method press

Ground Balance then raise and lower the

coil from about 10cm to the ground and

using the + and - buttons. Adjust until there

is little or no change in the high and low

tones. Auto is the same but is self adjusting

as you raise and lower the coil.

Having three ways of Ground Balancing

may seem a little complex or even

unnecessary but in practice it is very simple

and ensures any level of user can achieve

satisfactory Ground Balancing.

With both modes set up I began detecting

in the C&T mode. The Threshold remained

stable apart from the odd, very fast null,

a sweep or two in All Metal confirmed this

was iron. Before long a crisp high tone was

heard. This turned out to be two pre

decimal pennies laid together from a

depth of about 14cm. A little further on

a lower tone and a reading of 18 produced

a fragment of the aluminium alloy that

litters this site.

I continued across the paddock for the

next half an hour or so, digging various non

ferrous bits and pieces of various sizes. Two

things became apparent as I did this; Depth

and Sensitivity are very good, impressive

even. The second is that ‘iron reject’ is good

but the odd bit did get through which I put

down to the power that has been built into

the detector. Although this was not a big

problem as any iron signal was jumpy on

the meter and the audio was crackly or

‘woolly’ where as a non ferrous sound,

however faint, is solid and the meter

locks on… give or take a number or two.

Illustration from the Instruction Manual with permission from Minelab

Using the two modes back to back did

prove successful. On a couple of occasions

there was no signal on switching back to

C&T and each time a deep non ferrous

target was uncovered. One particular

signal was interesting; a clear signal was

encountered and the iron mask would not

jump in no matter how I approached it.

Assuming it to be a good signal I double

checked C&T. There was the faintest of

signals, so faint it would have missed it

had I not already known of its presence. On

digging, a copper alloy scoop was unearthed

from a depth of about 15cm. This was

positioned vertically in the soil and so did

not provide a good surface area for the coil

to ‘see’. When you consider that the C&T

mode is very good in its own right, the

level of audio given by this object in the

Prospecting mode was impressive to say

the least.

The next step was to try the X-terra 70

in Prospecting Mode. And boy is this mode

a different animal! In this mode you are

working with a VCO (Voltage Controlled

Oscillator) whereby there is an increase

in volume and pitch when a target is

encountered. There is no form of ID, simply

an audio signal for accepted targets and

even then a slow sweep speed is required

to allow the Discrimination (or Iron mask

as it is referred to in Prospecting) to jump

in (it takes a fraction of a second and does

literally jump in). I found with larger bits

of iron this was no problem but with smaller

bits it could be fooled and these were

identified by switching back to C&T.

I continued for the rest of the session in

Prospecting but finding it useful to be able

to refer back to C&T for reference, which

at the push of one button is no problem.

All target information in Prospecting has to

be gleaned from the audio and this is where

the learning curve lies. The more I used this

mode the more I liked it and couldn’t help

feeling that with experience I could use

this on all but the ‘junkiest’ of sites.

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