Whenever we install a sensor in the field, it’s always helpful to make sure it is reading properly before connecting it to the datalogger. Having a display to show the live data from a sensor is also helpful when doing calibration and testing of the sensor in the lab. We use a variety of sensors from Decagon Devices. Their high-quality, research grade sensors output the data in two formats – serial TTL and SDI-12. It is very simple to read the serial TTL data using an Arduino board. If you want to connect multiple sensors to the same pins, then you’ll want to switch to the SDI-12 format, because it allows you to assign a unique address to each sensor so you can have multiple sensors connected to the same pins. (see the SDI-12 library post – link).
Utilizing the SDI-12 library in the Arduino code, I built a handy sensor display box using an LCD display and a Sparkfun ArduinoPro board. The board captures the SDI-12 string from the sensor, recognizes the type of sensor (each type Decagon sensor sends a unique model number on SDI-12 initialization) and displays the data on the LCD. The data is updated whenever the user presses the button on the end of the enclosure.