The purpose of grounding, also known as earthing, is to create a direct path to ground through which ESD can travel without passing through sensitive equipment.
We recommend two grounding points per external microphone, and we recommend not grounding the external battery if you are using one and if not grounding it is otherwise allowed.
The first recommended grounding point is at the microphone itself. If electricity discharges towards the microphone, the least destructive path it can take is directly to ground, as this avoids damaging the microphone and the Song Meter. For plastic-bodied microphones like the SMM-U2, a metal grounding bracket provides a means to divert electricity to ground. For metal-bodied microphones, the body of the microphone can be directly wired to ground.
The second recommended grounding point is at a surge suppressor installed along the cable in between the microphone and recorder. The Wildlife Acoustics Microphone Surge Suppressor is designed to redirect electrical surges that travel down the microphone cable away from the recorder to ground.
Grounding the SMM-U2
The plastic body of the SMM-U2 ultrasonic microphone cannot be directly wired to ground. Therefore, you should install and ground the SMM-U2 Grounding Bracket. The bracket provides a conductive surface to intercept any ESD that might otherwise leap to the microphone's electronics.
The grounding bracket should be securely connected to a grounded structure, such as the metal body of a meteorological tower, using a heavy-gauge wire.
Grounding Other Microphones
Metal-bodied microphones, including the SMM-U1 and SMM-A2, do not require a grounding bracket accessory. Instead, a heavy-gauge wire should be clamped directly to the microphone's metal body and connected to a grounded structure.
Not Grounding an External Battery
If you power the Song Meter with an external battery, we recommend not connecting the battery to ground if you are not required to do so.
Grounding the battery creates a path from the microphone to ground that passes through the Song Meter. By not grounding the battery, you increase the likelihood that ESD will travel straight to ground through the intentional grounding points on the microphone and surge suppressor rather than through the Song Meter.
At some deployment sites, you may be required to ground the external battery. In these cases, grounding the microphone and surge suppressor and using ferrite beads still provide protection.