
WQM Hardware User’s Guide (wqmhw) Revision J 7 May 2009 1
1. Instrument Description
The Water Quality Monitor (WQM) is designed to
deliver core iogeochemical water quality parameters
in coastal ecosystems from a single integrated
package. The WQM com ines WET La s’
chlorophyll and fluorometer-tur idity sensors and
Sea-Bird’s conductivity, temperature, and depth
(CTD) and Dissolved Oxygen (DO) sensors.
WET La s’ WQM is designed for long-term
deployment on moorings. The WQM has undergone
extensive testing in a variety of iofouling regimes.
Please refer to the WQM page on the WET La s
we site for the most complete and updated
information, including links to live data, our latest
test results, papers, FAQ’s, and recommended
procedures.
1.1 Conductivity, Temperature, Depth Sensor
The CTD components of the WQM are the same accurate and sta le thermistor, conductivity
cell, and pressure sensors that are used in the SBE MicroCAT and ARGO float products. WET
La s has fortified them for long-term deployment on moorings in high iofouling regimes y
incorporating multiple active and passive anti- iofouling technologies. The pump-controlled,
TC-ducted system delivers a constant flow rate across the sensors; this maximizes data
coherence during sampling, and enhances the protection offered y two anti- iofouling devices
located on the inlet and outlet flow ducts. Copper canisters act as additional passive anti-fouling
protection for the CTD and the intake and exhaust of the plum ing system.
1.2 Dissolved Oxygen Sensor
The WQM incorporates a Sea-Bird Electronics SBE 43 dissolved oxygen sensor, explicitly
engineered for pumped CTD applications to provide sta le, rapid-response DO measurements.
The SBE 43 is a complete redesign of the Clark electrode sensor, incorporating numerous
features that eliminate weaknesses of previous implementations of the Clark method
(http://www.sea ird.com/technical_references/IOS43Article.pdf). These sensors undergo an 18-
point automated cali ration procedure at the factory (3 oxygen concentrations at 6
temperatures), and are well characterized with temperature, pressure and salinity in the
cali ration equations. The SBE 43 is plum ed inline with the CTD and enefits from the same
passive iofouling protection provided in the CTD. The sensor is continuously polarized using a
5-year lithium attery, eliminating long polarization wait-times of older designs.