Intrinsically safe wireless dongle for a field device

1. A wireless dongle for an automation field device, in particular a two-wire field device, to connect to an electrical interface of a field device, having:

a wireless circuit for sending or receiving wireless signals;

a printed circuit board; and

a connector element, wherein:

the wireless dongle can be fitted detachably to the electrical interface by means of said connector element;

said connector element has several contact elements, said contact elements are attached to said printed circuit board in the wireless dongle;

a first contact element is used to supply the wireless dongle with energy;

an energy buffer is provided which is downstream of said first contact element, that said connector element has a second contact element which is used to transmit data between the field device and the wireless dongle;

at least one limiting resistor is downstream of said first contact element and downstream of said second contact element; and

said at least one limiting resistor and said energy buffer of the wireless dongle are encapsulated by means of a potting compound.

2. The wireless dongle according to claim 1 , further having:

a DC converter which is downstream of said energy buffer, wherein:

said DC converter is used to control the voltage which is made available to said wireless circuit.

3. The wireless dongle according to claim 2 , wherein:

the wireless dongle is designed such that a first operating voltage operates said energy buffer, that a second operating voltage operates said wireless circuit, and that said DC converter converts said first operating voltage to said second operating voltage.

4. The wireless dongle according to claim 1 , further having:

a first monitoring arrangement monitoring the energy in said energy buffer, wherein:

said first monitoring arrangement has a switch which is initially in an open state between said energy buffer and said wireless circuit, and that the switch is closed when the energy in said energy buffer exceeds a prescribed threshold value.

5. The wireless dongle according to claim 1 , further having:

a second monitoring arrangement which monitors the energy supply of the wireless dongle and, in the event that the energy available for operating the wireless operation of the wireless dongle is below a prescribed threshold value, switches off the wireless operation.

6. The wireless dongle according to claim 1 , further having:

a third contact element which is part of a second data transmission line which transmits data from the field device to the wireless dongle, and a limiting resistor is downstream of said third contact element, wherein:

said second contact element is part of a first data transmission line which transmits data from the wireless dongle to the field device.

7. The wireless dongle according to claim 6 , further having:

a level converter, wherein:

said first data transmission lines on said second and third contact element have a first voltage level, that said first and second data transmission lines on said wireless circuit have a second voltage level; and

said level converter converts the voltage level.

8. The wireless dongle according to claim 7 , wherein:

said first operating voltage corresponds to said first voltage level, and said second operating voltage corresponds to said second voltage level.

9. The wireless dongle according to claim 6 , further having:

a fourth contact element which is connected to ground, wherein:

said energy buffer is a capacitor;

a first electrode of the capacitor is connected to a node downstream of said first contact element; and

a second electrode of the capacitor is connected to said fourth contact element.

10. The wireless dongle according to claim 1 , wherein:

the wireless dongle has a hermetically sealed enclosure and, that said enclosure is at least partially filled with said potting compound.

11. The wireless dongle according to claim 1 , further having:

an antenna integrated into the wireless dongle, wherein:

said energy buffer, said wireless circuit and said antenna are all encapsulated via said potting compound.

12. The wireless dongle according to claim 1 , further having:

an antenna integrated into the wireless dongle whose antenna feeder is separated from said energy buffer by at least one blocking capacitor, wherein:

said at least one blocking capacitor is encapsulated together with said energy buffer and the wireless circuit via said potting compound.

13. The wireless dongle according to claim 1 , further having:

an encryption unit integrated in the wireless dongle which is used to secure said wireless channel against being tapped and/or manipulated.

14. The wireless dongle according to claim 13 , wherein:

said encryption unit has a non-volatile memory in which information such as passwords or keys is stored.