Connection of an Ex nA digital indicator to an Ex i sensor

Is it possible to connect a non-incendive Ex nA digital indicator to an intrinsically safe Ex i sensor in hazardous areas? Frequently, signals from pressure sensors that not have a built-in digital indicator for the measured value are linked to external digital indicators. These digital indicators enable an on-site display of the measured value and, thus, a convenient and immediate reading of, for example, the level in storage vessels.
Pressure sensors for hazardous areas are generally made with the ignition protection type ?intrinsically safe?, since this allows interventions in an active electrical circuit and less energy is needed. However, this also means that there is insufficient energy designed for a powerful measured value display. Because of this, digital indicators tend to be made with ignition protection types that enable more current and voltage to be allowed. Frequently, digital indicators are designed as ?non-incendive? (Ex nA). This ignition protection type enables power-hungry instruments to be operated in Ex areas too. However, Ex nA is limited for use in zone 2 ? so in areas where an explosive atmosphere only rarely occurs.
The right connection of digital indicator and barrier
Non-permissible connection of an Ex i pressure sensor with isolated barrier and Ex nA digital indicator.
pressure gauge requires an intrinsically safe barrier for its voltage supply, in order that the interconnection is considered as intrinsically safe and the huge benefits, such as for example maintenance work with no need for a fire certificate, can be utilized. Digital indicators are generally integrated as passive element, with or without an external power supply, directly in the 4 ? digital pressure gauge of a sensor. Since an Ex nA digital indicator has no Ex i performance data in its approval, it cannot therefore be used in a ?Proof intrinsic safety?. Therefore, an Ex nA indicator can’t be connected within an Ex i circuit.
เกจวัดแรงดัน of an Ex i pressure sensor with isolated barrier and Ex nA digital indicator.
There is, however, the chance to connect a digital indicator with an Ex i pressure sensor in zone 2. The prerequisite is that the intrinsically safe isolated barrier also possesses an Ex nA approval and should be installed in zone 2.
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Should you need any help with selecting a suitable solution for your pressure measurement requirement, your contact person will gladly help.

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