SIL Safety Manual
Scope
This safety manual applies to the loop-powered isolators of the ProLine P224xx P1
series. The defined safety function of the devices is for the input signal range of
4 to 20 mA. The loop-powered isolators of the ProLine P224xx P1 series of Knick
Elektronische Messgeräte GmbH & Co. KG are certified by TÜV.
General Description
The loop-powered isolators of the ProLine P224xx P1 series were developed accord-
ing to SIL 3. The loop-powered isolators have no diagnostic function.
In single-channel mode, they are of Category 1 and have Performance Level c
according to the Machinery Directive 2006/42/EC.
Applicable Standards
The loop-powered isolator can be used in safety-related applications up to SIL 3
(systematic suitability). The standards relevant for the application shall be applied
(for example, EN 61508, EN 61511, EN 62061, and EN ISO 13849).
Safety Functions
The loop-powered isolator transmits a 4 to 20 mA measurement signal galvanically
isolated to the output. The input signals are transmitted linearly at a ratio of 1:1.
The error signal is defined for the ranges of < 3.6 mA or > 21 mA. The analog output
signal needs to be evaluated by a downstream logic unit (such as F-PLC).
With dual-channel redundant operation (1oo2), the values must be compared.
When a specific tolerance is exceeded, a safe state must be achieved.
Signal Level for Measurement Signal and Failure Information
Information
Measurement signal
Failure information (error)
Signal level
4 ... 20 mA
< 3.6 mA ; > 21 mA
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