The Lawson Labs, Inc. Model 301 24-Bit Data Acquisition System is a high-resolution device for
translating voltages into digital form. The Model 301 communicates with a host computer using USB (Universal Serial Bus).
It has two multiplexed differential analog input channels and eight each digital input and digital output lines. The analog
input and digital I/O sections are optically isolated from the computer.
The Model 301 is intended for DC and low frequency applications. The data rate is programmable from 50
to 1000 samples/second. At a data rate of 50 samples/second, the RMS noise approaches one count, providing 23 bits effective
resolution. (The converter is guaranteed monotonic to 23 bits.) Effective resolution decreases with increasing data rates.
Even so, 20-bit effective resolution is maintained at 1000 samples/second.
The Model 301 requires a single DC supply in the range of 9 to 15 volts to power the isolated circuitry. With the optional
preregulator, the range is 15 to 30 VDC. Current draw is typically 25 milliamps in normal operation. The power and analog
inputs are protected against substantial overvoltages.
Both polled and scanning modes are available. In scanning mode, the Model 301 maintains its own time base and transmits
a pre-defined scan of one or two input channels at a preset interval. Self-calibration can remove offset and gain errors
under software control.
The exceptional resolution, stability, flexibility and price are achieved by combining an accurate, but complex,
delta-sigma type A/D converter with a microcontroller supervisor. The microcontroller simplifies the task of interfacing to
the converter itself.
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