WP-1 Sensor Specification and Development along with Interface, Dr. Zhaohui Aleck Wang & Dr. Indra S Sen

Development of Water Quality Sensor (Wang, WHOI)

Objective

The overall objective of sensor development in this project is to develop low-cost, robust,and miniaturized in situ water quality sensor packages for deployment on the stationary and mobile platforms in river systems. The sensor packages will also be versatile and suitable for stand-alone or other deployments in aquatic systems. The water quality parameters to be measured by the sensor package include dissolved oxygen (DO), pH, conductivity (salinity), temperature, total C02, and dissolved copper. If time permits, we will also include dissolved cadmium in the suite of measured parameters.

MINI-DO Sensor


Wang’s group at WHOI is currently developing an in situ mini-DO sensor (through another funded project) that can be deployed on small marine organisms, such as jellyfish and squid (Figure 1). The measurement method is based on a well-established fluorescence quenching method. The original sensing component is commercially available and low cost. The sensor is redesigned and engineered to be small in size (about the size of a coin), low power ( 0.3W), and deploy-able in situ up to 300m. Currently, the DO sensor is under bench testing, followed by in situ testing in the ocean. It will be available for this proposed project for integration with other sensing components. The sensor will have an accuracy of 0.5% 02 and a detection limit of O.l%.

Fig:-MINI-Do Sensor and Testing Electronic Assembly

MEMS Conductivity and Temprature Sensor

  1. Through the above mentioned project, Wang’s group is also developing a Micro-Electrical-Mechanical Systems (MEMS) for in situ measurements of conductivity (salinity)- temperature sensor on
    jellyfish and squid (Figure 2). Such a MEMS sensor has been widely deployed as bio-tags on larger marine.
  2. Such a MEMS sensor has been widely deployed as bio-tags on larger marine animals and fishes to measure seawater salinity, temperature, and pressure [Hyldgard et al. 2005]. Our recent development is to further reduce the size and power consumption (<0.3 W) so that it can fit  on small marine organisms.
  3. Currently, these MEMS sensors are being built in Wang’s lab.
  4. We will conduct laboratory and field testing in the coming months. For this proposed project, we will integrate the MEMS temperature-conductivity sensor along with other sensors in the sensor package.
  5.  The measurement precision and accuracy of the sensor will be 0.1°C for temperature and 0.1 pst for salinity.

ISFET pH Sensor


We will also purchase a commercially available ion sensitive field effect transistor (ISFET) pH  sensor (e.g., Honeywell Durafet pH sensor) and incorporate it into the sensor package. ISFET pH sensor has
been widely and successfully used in both seawater and freshwater environments [Martz et al., 2010] [Bergveld 2003]. It has the advantages of small in size, less drifting, low power consumption, and
low cost. We will engineer it to fit into the sensor package and calibrate it in river water. The measurement will have a precision of 0.01 pH units, and an accuracy likely 0.02.

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