Two-channel Analog-to-Digital converter board with USB interface

build an interface board to connect some scientific equipment (for me, a pair of photovoltaic tubes) to a personal computer to acquire measurements results. Signal properties were following: two channels with a common ground, 1 second of acquisition time, max 10V signal level. Desired digitizing properties were about 1000 samples per acquisition, 10 bit depth. The most attractive

and cheap solution is to use a PC sound card as an ADC converter. However, most of laptop computers have only mono low-level microphone input onboard. After a careful research, a Texas Instruments PCM2900 chip [1] was chosen as a proper converter (fig. 1). It has a stereo I/O (only input is used in this project), USB interface and MS Windows drivers already shipped with an OS. A reference board design from TI was used (fig. 2). One can easily found it in the data sheet [2]. Output circuits were removed, and proper capacitors selected. C9 and C10 capacitors were removed as input signal have zero frequency (DC). Instead, a couple of potentiometers (5K and 10K) were placed to do fine board tuning. After an assembly has been finished, the board was plugged onto my PC (Windows XP): Check the "USB HID", "USB Audio device" and "USB Composite device". Also I had to specify a new source for sound recording.

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