Mettler Toledo IND560x Manual De Instalación página 72

An example of how to wire to the active inputs is shown in Figure 3-37.
3.4.2.2. Active Outputs
Using the Discrete I/O option with active outputs enables direct connection of low-power intrinsically
safe solenoids or piezo fluid control valves. The terminal provides the intrinsically safe voltage
internally making the output active and no external voltage is required by the external simple
device. The source power is approximately12 VDC at a 50mA total current. All outputs operate from
this single power source.
The IND560x Active Output option uses internal series resistors to limit the power to I.S. levels.
These internal resistors have the following effects on the Active / Active I/O option:
• Increasing the current draw has an inverse effect on the voltage available to the control device.
• The voltage will drop depending on the current required to operate the solenoid.
Estimates on available voltage based on current draw are shown in Table 3-11.
3-28 METTLER TOLEDO IND560x Installation Manual
In hazardous dust applications, the Table 1 of EN/IEC 61241-11 has to be taken into account,
e.g. for the certified Po = 2,94mW the relevant regulation is to apply and II2D approved input
devices should be used.
FM guideline for connection to the active input: Using simple apparatus as defined by section
504.2 of the National Electric Code (NFPA 70) is "An electrical component or combination of
components of simple construction with well-defined electrical parameters that does not
generate more than 1.5 volts, 100 milliamps, and 25 milliwatts and is compatible with
intrinsic safety of the circuit in which it is used."
The Section 504.4 exception in the NEC states that "Simple apparatus, as described on the
control drawing, shall not be required to be listed."
Figure 3-37: Active Input Connections
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