Smartac Board Characteristics; Interaction With The Welding Equipment And Weldment - ABB SmarTac Applications Manual

3.3 SmarTac board characteristics

3.3.1 Interaction with the welding equipment and weldment

SmarTac board
The SmarTac board (alone) is capable of generating a stop signal from
high-resistance surfaces with up to 1 Mom contact resistance. In real applications,
however, the SmarTac sensing circuitry is normally loaded from the surrounding
welding equipment. The electric equivalent diagram below explains the situation.
Sensitivity
Maximum sensitivity will only be obtained when using a separate, highly insulated
probe (not supplied).
Electric equivalent diagram
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Convection-cooled welding gun
SmarTac used with a convection-cooled (air cooled) welding gun will loose some
sensitivity due to losses through the weld equipment. In the circuit above, this loss
is described by resistor #2.
Positive lead secondary contact
In systems with a positive lead secondary contact, the loss through the weld
equipment is eliminated.
Application manual - SmarTac
3HAC024845-001 Revision: A
3.3.1 Interaction with the welding equipment and weldment
Electrically conducting cooling
water or other low impedance
bridges in the welding gun, for
example, deposits from the
welding process
Open circuit impedance between
the weld power source terminals
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Smartac positive terminal
0
Gas nozzle (probe)
1
Work surface coating
2
3
0
Smartac negative terminal
3 Application guide
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