7
SDI-12 OPERATION DETAILS
Overview
The LISST-AOBS supports numerous SDI-12 commands for flexible control
over the timing of samples, and over the anti-fouling wiper on the
Turbidity Plus. All these commands are accessible to any logger that
supports version 1.3 or higher of the SDI-12 protocol. For complete details
of the LISST-AOBS commands, see
Addressing
When shipped from Sequoia Scientific, the LISST-ABS is normally set to
address 0 (zero). You can change the addresses according to your own
requirements, using standard SDI-12 methods. In this document, we use
a
to represent the LISST-ABS address.
Sampling and
averaging
The ABS and turbidity sensors in the LISST-AOBS can be sampled every 2
to 3 seconds, using the SDI-12
M
command. However, we recommend
collecting 30-second averages in most cases, to smooth the natural
variability created by turbulent motion of particles. Longer averaging
intervals are also available by selecting the appropriate commands. The
concurrent C commands allow the logger to communicate with other SDI-
12 devices while the LISST-AOBS collects and averages its readings.
Control of the
anti-fouling
wiper
By default, the wiper on the Turbidity Plus runs once when power is
initially applied to the LISST-AOBS. If your logger is programmed to turn
off power to the LISST-AOBS between samples, the wiper will run upon
power-up before each sample, without an explicit command from the
logger. However, you can also turn off the automatic wiping and control
the wiper with commands via RS-232 or SDI-12. See
on page 11.
