  Metallic pipes and other containers are widely used to store and transport
toxic gases and liquids. Various sensors have been designed to monitor the
environment inside metallic pipes and containers, such as pressure,
liquid-level, and chemical sensors. Moreover, sensors are also used to inspect
and detect pipe leakages. However, sensors are usually placed outside of
metallic pipes and containers and use ultrasound to monitor the internal unseen
environment. This is mainly due to the fact that internal sensors cannot
communicate with external data sinks without cables, but using cables can
dramatically affect the metal-sealed structure. Wireless communication is
desirable to communicate with internal sensors, but it experiences high
attenuation losses since metal can block wireless signals due to its high
conductivity. This paper develops a low-cost through-metal communication system
prototype using off-the-shelf electronic components. The system is fully
reconfigurable, and arbitrary modulation and coding schemes can be implemented.
We design the transmit module which includes a signal processing
microcontroller, an amplifier, and a transmit coil, and the receive module
which includes a receive coil, an amplifier, and a microcontroller with
demodulation algorithms and bit-error-rate (BER) calculations. The performance
of the prototype is evaluated using various symbol rates, distances, and
transmission power. The results show that the communication system can achieve
a 500 bps data rate with 0.01 BER and 3.4 cm communication range when
penetrating an Aluminum pipe with 7 mm thickness.
