Whites TDI SL Owner's Manual download pdf (Page 14)

Page 14

TDI SL

Owner’s Manual

TDI In Depth

Ground Balancing

One of the key features of TDI is its ability to balance out

ground mineralization while maintaining pulse induction

depths. This is achieved using a differential technique whereby

two decay samples are compared; the Ground Balance control is

adjusted until the two samples have the same response, thereby

canceling the ground signal.

Targets below the GB point produce an overall positive

response, and targets above the GB point produce an overall

negative response. Broadly, the two ranges of targets depend on

conductivity, which gives TDI some ability to discriminate. In

rare cases a target might fall so close to the GB point that it

gives either no response at all or a double-tone response.

Because ground balance is achieved using a subtraction

method, there is a slight loss of depth any time ground balance

is on. Some ground, notably neutral beach sand, is mild enough

that no ground balance is needed. In such cases, Ground Bal-

ance

can be switched off and TDI will run in straight PI mode.

This will slightly improve depth, but loses the ability to distin-

guish between low and high conductivity targets.

Audio

TDI has the following audio tonal responses:

Low

Conducto

High

Conductor

On High ‐‐‐ Low

On All High Low

On Low High ‐‐‐

Of f ‐‐‐ High High

AudioTones

Ground

Balance

Conductivity

Mode

1 2 ... 9 10 11 12 13 14 15 16 17 18 19 ... 23 24

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Whites TDI SL Owner's Manual Page 14