Specifications

19
Chapter 3
Product Definition
This chapter includes details on how the product requirements were further refined from
section 1.3 and how the design of a new DataManager was approached and decomposed
into various sub-components.
3.1 Design Requirement Survey
Discussions between the author, Acclima, and other stakeholders resulted in a more
complete list of requirements for a new logger platform, enumerated below:
1. The device must be able to ru n on commonly available and inexpensive AA-, C-, or
D-cell battery power for a period of eight months to a year. The general consensus is
that is must last a growing season. For some producers in California, that is all year
round.
2. The device must s upport auxiliary power from external batteries or 6/12V solar
power. Th e device will th erefore have a power input port that can handle at least
15VDC.
3. The device must support variable switched power terminals to supply sensors with
power. Many sensors need excitation voltages to perform measurements. Other sen-
sors need different voltage levels than what field site battery can sup ply. Still other
sensors can draw too much current if conn ected to a battery directly. Consequently,
“variable” is interpreted as being able to supply 6V, 9V, 12V, and 15V at 500mA.
4. A single device must not cost more than $800, with a target cost of $600.
5. Each device must come in a weather proof enclosure and have a built-in lock. This
requirement has two purposes. One is to reduce the cost of installation by not requiring