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

Is diaphragm seal 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 an integral 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 frequently made with the ignition protection type ?intrinsically safe?, since this enables 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 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 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.
เกจวัดแรงดัน requires an intrinsically safe barrier for its voltage supply, so the interconnection is recognized as intrinsically safe and the benefits, such as maintenance work without the need for a fire certificate, can be used. Digital indicators are frequently integrated as passive element, with or lacking any external power, directly in the 4 ? 20 mA current signal of a sensor. Since an Ex nA digital indicator 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 cannot 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 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 must 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
In the event you need any help with selecting a suitable solution for your pressure measurement requirement, your contact person will gladly help.

Scroll to Top