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

Is it possible for connecting a non-incendive Ex nA digital indicator to an intrinsically safe Ex i sensor in hazardous areas? Very often, signals from pressure sensors that 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 instance, the particular level in storage vessels.
Pressure sensors for hazardous areas are frequently designed with the ignition protection type ?intrinsically Signs ?, since this enables interventions in an active electrical circuit and less energy is necessary. However, this also implies that there’s insufficient energy available for a powerful measured value display. Subsequently, digital indicators tend to be made 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 bound for use in zone 2 ? so in areas where an explosive atmosphere only rarely occurs.
The proper connection 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, so the interconnection is considered as intrinsically safe and the huge benefits, such as maintenance work without the 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 ? Brutal of a sensor. Since an Ex nA digital indicator has no Ex i performance data in its approval, it cannot therefore be utilized in a ?Proof of intrinsic safety?. Therefore, an Ex nA indicator cannot be connected in an Ex i circuit.
Correct connection of an Ex i pressure sensor with isolated barrier and Ex nA digital indicator.
There is, however, the possibility 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 should be installed in zone 2.
Read also our articles
Ex barrier and intrinsically safe pressure sensors ? an inseparable pair
Proof intrinsic safety for an ATEX-approved pressure sensor
Note
Should you need any help with choosing a suitable solution for your pressure measurement requirement, your contact person will gladly be of assistance.

Leave a Comment