Data Logger Use in Environmental Monitoring

With worldwide concern about global climate change the use of data logger equipment to monitor a wide range of environmental factors such as temperature, solar radiation, rainfall, and water table levels is becoming increasingly prevalent.

Many modern data logger models offer long operation on internal batteries coupled with multi channel universal input capability. This makes them ideal for use in the field with a variety of environmental sensors. The basic data logger inputs required for these sensors are listed below:

Data Logger Temperature Sensor Inputs
The three main types of temperature sensors are thermocouples, PT100 sensors and thermistors. Thermocouples require a data logger with high resolution and cold junction compensation. Thermocouples do not require external power making them ideal for use with data logger installations in remote locations. Thermistors are low cost and accurate, but are non linear so the data logger needs an internal look up table to read these devices accurately. PT100 sensors are very accurate, but as they are three wire devices many low cost data logger models are not compatible.

Data Logger Rain Gauge Inputs
A rain gauge is a barrel shaped device with a rain collector. The collector funnels the rain water onto a tipping bucket sensor. When the bucket fills up it tips, triggering a pulse from a reed switch to measure 0.2 of a millimeter of rainfall. A data logger must have a pulse input to work with a rain gauge.

Data Logger Inputs for Solar Radiation Sensors
Whilst many low cost data logger models can work with temperature sensors and rain gauges, the very low voltage output of solar radiation sensors can present a problem. With a typical range of 0-20 mV to represent a range of 0-2000 WM2 a data logger needs a very low measurement range and high resolution to take meaningful readings.

Data Logger inputs for Water Level Sensors
Water level sensors are usually submersible pressure sensor types or ultrasonic non contact. As most pressure based depth sensors require excitation the data logger needs to be able to power the sensor. Many data logger models have a five volt supply available for this type of sensor. For use with ultrasonic level sensors the data logger needs to be able to power a 4-20mA loop.

Data Logger Inputs for Wind Sensors
These are available with voltage, mA and serial outputs. Whilst most data logger types can handle voltage and current inputs few are able to read serial devices. The new generation of Omni Instruments data logger models support the serial protocols used by the latest wind sensors.

So it can be seen that for environmental monitoring applications it is important to select a data logger with multi channel input capability which is able to support a wide range of sensor inputs

Omni Instruments has many years of experience of providing data logger equipment for these applications and can also supply compatible sensors.

Jim Furness is CEO of Omniinstruments Ltd, specialists in data logger and other instrumentation solutions