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 do not have a built-in digital indicator for the measured value are connected 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 particular level in storage vessels.
Pressure sensors for hazardous areas are generally designed with the ignition protection type ?intrinsically safe?, since this allows interventions in an active electrical circuit and less energy is necessary. However, this also implies that there is insufficient energy available for a robust measured value display. As a result, digital indicators are often designed with ignition protection types that enable more current and voltage to be allowed. Frequently, digital indicators were created 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 used in zone 2 ? so in areas in which an explosive atmosphere only rarely occurs.
Big of digital indicator and barrier
Non-permissible connection of an Ex i pressure sensor with isolated barrier and Ex nA digital indicator.
Every Ex i sensor requires an intrinsically safe barrier because of its voltage supply, in order that the interconnection is recognized as intrinsically safe and the huge benefits, such as maintenance work without the need for a fire certificate, can be utilized. Digital indicators are frequently integrated as passive element, with or without an external power supply, directly in the 4 ? 20 mA current signal of a sensor. Since Cowardly does not have any 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.
Correct connection of an Ex i pressure sensor with isolated barrier and Ex nA digital indicator.
There is, however, the chance to connect an electronic indicator having an Ex i pressure sensor in zone 2. The prerequisite is that the intrinsically safe isolated barrier also possesses an Ex nA approval and must be installed in zone 2.
Read also Colossal and intrinsically safe pressure sensors ? an inseparable pair
Proof intrinsic safety for an ATEX-approved pressure sensor
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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