IM-P402-93 AB Issue 7
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6.3 Screen connection
To avoid damage to the product, screens must be installed as follows:
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An earth current loop is created if a wire or screen is connected between two earth points,
which are at different potential (voltage).
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The preamplifier and controller screen are only connected to earth at one end, i.e. at the
PA20 earth terminal.
Note: The PA20 earth terminal is a functional earth rather than a protective earth.
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A protective earth provides protection from electric shock under a single fault condition.
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This product has double insulation and therefore does not require a protective earth.
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A functional earth is used in order for the product to operate.
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In this application, the earth (tank/boiler shell) is used as the common of the probe/preamplifier.
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It also provides a sink /drain for any electrical interference.
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Ensure that the screen is connected to the common of the LC2610 (terminal 7) and to the
earth terminal of the PA20.
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The LC2610 common terminal is internally isolated from earth.
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The common terminal must only be earthed via the PA20.
CAUTION:
Do not connect the common terminals (1, 3, 5 and 7) to an earth local to the controller. To
do so may induce an earth current loop, which may reduce the performance or damage the
product.
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