Specifications

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12VDC power, ground, and a 5V-TTL bidirectional data port must be supported. The
SDI-12 module mu st support nine sensors while using the standard set of device addresses
(universal 0 and 1-9). The device must support one port and have individual configurations
for all nine sensors. These configurations mu st support multiple power settings and start
up delay parameters.
3.2.4 Analog Measurement Module
The analog m odule is the second installment that aims to satisfy the general interface
requirement. It must have two different measurement modes: current loop and single-ended
(SE) voltage measurement modes. In current loop mode, this module will need to reliably
measure 0-20mA with 2µA accuracy. In SE voltage mode, the module must support an
auto ranging voltage input capable of measuring the following ranges: 0-1.5V, 0-2.5V, 0-
6V, and 0-10V. The module will consist of three powered measurement ports. Individual
configuration for the three ports must support multiple power settings and start up delay
parameters. There will be no extra sup port for differential voltage, high resolution, or
pre-amplified measurements.
3.2.5 Digital Measurement Module
The digital module is the third and final installment in the design’s attempt to satisfy
the general interface requirement. Two ports must be supported by this module. Both
ports must support s ep arate inpu t sampling with a timer reference, one power port, and
have transient and over-voltage protection and be 5V-TTL tolerant. The mo dule must
support separate configurations for both ports.
3.2.6 Switched Power Module
The Sw itch Power Mo dule controls the output and timing of all the power ports. This
module satisfies the general requirement that all sensors can be powered by the device.
One port must be associated with every SDI-12 and analog port, as well as one for the two
digital ports. All ports mu s t be capable of outputting 6-15VDC with an output current of