Sequoia LISST-ABS X2 Integration Guide

Sequoia Scientific’s LISST-ABS Turbidity Sensor is a single-point acoustic sediment sensor. The sensor initially measures Attenuation Corrected Backscatter that is then converted with an internal multiplier to a Suspended Particles (mg/L) measurement. The LISST-ABS is compatible with the X2 data logger using the SDI-12 communication protocol and sensor interface. Below is information on the settings and wiring required to integrate the sensor with the X2 data logger.

Sequoia Scientific LISST-ABS Turbidity Sensor product page

Figure 1: Sequoia Scientific LISST-ABS Acoustic Backscatter Sensor



NexSens UW8 Connector Wiring & Pin Information

In the event of connecting a NexSens UW8 connector into an external device that is not an X2 data logger, below is the pinout of the NexSens UW8 connector, along with the signal associated with the communication, ground and power pins from the sensor.

Figure 2: NexSens UW8 plug pinout.


NexSens UW8 Pin NumberSignal


Configure Communication

For the X2 data logger, the SDI-12 communication protocol and the unique address of the sensor are the most important settings. If another sensor on the X2 communicates via the SDI-12 protocol, each sensor must have its own unique SDI-12 address.

  • Using an external controller with an SDI-12 terminal communication, enter the following command to change the sensors unique SDI-12 address:
    • Syntax: aAb!
      • a is the current sensor address.
      • A is the change address command.
      • b is the new address of the sensor.
      • ! terminates the command.
    • Example:
      • 0A1!
        • Requests that the sensor changes its SDI-12 address from 0 to 1.
    • ┬áResponse
      • b<CR><LF>
        • b is the new sensor address and <CR><LF> terminates the response.


X2 Script Information

The X2 data logger includes a pre-loaded Sequoia LISST-ABS turbidity sensor script that will detect the unique SDI-12 address of the sensor, along with the X2 sensor port in which it is connected. Use the CONNECT software to enable the script for sensor detection.

Configure Sensor Scripts

X2 Script NumberCommunication ProtocolBaud RatePower TypeWarmup Period (Sec)Frame


Script Parameters

The Sequoia LISST-ABS turbidity sensor outputs a single Suspended Particle (mg/L) parameter. The sensor utilizes acoustic backscatter to measure the concentrations of particles suspended in the water. Its initial “Uncalibrated Concentration” is based on measurements from 75-90 micron glass microspheres; however, users can adjust the calibration using a solution with a known composition and size of particles. This solution should be a representative sample of the particles sizes expected in-situ.

Sequoia recommends that the LISST-ABS collects a 30 second or longer average. The X2 utilizes the SDI-12 command M3 to provide a 120-second average (1Hz), providing reliable results over that time frame.


For more information, refer to the Sequoia Scientific LISST-ABS Turbidity Sensor User’s Manual.


Turbidity Measurements

Learn more about turbidity measurements in the Fondriest Environmental Learning Center.


Applicable Systems

Turbidity measurements from the Sequoia LISST-ABS sensor are useful in various environmental monitoring applications.