Data Acquisition (DAQ) and Control from Microstar Laboratories

Knowledge Base: Hardware

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Q10042 Capturing audio signals with microphones

Tags: Help, DAP, DAPL, sensors, audio, microphone, electret, sampling

Applies to: All DAP models, differential termination and isolation boards

Is it possible to capture audio signals using electret microphones?

Not only possible, it is possible on a grand scale. See the article cited in the references.

Microphone input circuit

The most straightforward way to connect microphones is illustrated in the circuit diagram. Electret microphones are available as an unpowered cartridge, but more commonly include a tiny integrated solid-state amplifier, without much cost difference. The power gain of the amplifier boosts the signal at the source, which is a big advantage for accurate signal transfers and data capture. The amplifier requires a trickle of power, typically a few milliamperes, from a power supply typically 9 to 18 volts – check your device specifications for the proper voltage level. The loading resistance RL is chosen as a best impedance match for the cartridge section. The coupling capacitor of 1 to 10 µF often is integrated into the microphone module. The transfer is through an unbalanced differential signal, avoiding noise pickup through a ground loop path. The termination resistance RT is typically about 100K, to provide a charge leakage path for the input converter devices.

An ICP configuration is also possible, in which the sensor amplifier is powered from the receiving end.

L----- describes a large-scale 3-D acoustic imaging project measuring jet airplane wake vortices.