Specifications

5.2.1 Phase One

This is the ﬁrst phase that others outside of Acclima were brought in to judge perfor-

mance and to help identify bugs. At this stage, the device need only support one SDI-12

sensor, the framework for the data logging scheduler, and basic WASUP communications.

Operations testing for SDI-12 devices included querying, change of address, adding, iden-

tifying, measuring, and removing one sensor. All this testing was done using the device

conﬁgurations and scheduler. Screen options allowed for conﬁguring and reading the sen-

sor. The basic WASUP interface was also in place to permit the PC to adjust device

properties and conﬁgurations.

The major problem id entiﬁed with the Data Manager at this phase was that 60% of all

units failed to add or read a sensor. The problem occured because the internal resistance

inherent in battery packs limited the instantaneous current surge required to charge up the

SDI-12 power line. This in turn caused the battery voltage to drop and the supervisory

circuit triggered a reset. This problem did not surface during alpha testing because the

device was being powered by bench power with suﬃcient supply. Three actions were taken

to remove this bug. First, the battery su pervisor interrupt was momentarily disabled to

allow for these dips during a sens or power up sequence. Second, the power sup ply was

redesigned to limit the surge current to a greater extent than the batteries. Lastly, system

and error logs were created to aid in post-mortem analysis of device failures. T his should

assist in the search process for other possible bugs.

5.2.2 Phase Two

At this stage, the device needed to support all designated sensor interface types and a

full complement of s en s ors , all LCD screens, and the SD card drive. The SDI-12 port was

expanded to handle the addressing of nine sensors. All analog and digital ports were also

fully integrated with the screens required to add, conﬁgure, and d irectly read sensors. The

SD card interface supporting a FAT ﬁle system also needed to be in place. The SD card

interface can format a drive and access and write to a directory structure that is recognized

by PCs.