Configuring SDI-12 Sensors

Configuring SDI-12 Sensors

SDI-12 stands for Serial/Digital Interface at 1200 baud. It is a protocol that covers the communication aspects between a sensor and a datalogger, such as the Data Logger device. SDI-12 protocol is an ASCII-based master-slave protocol. The data logger is the master, and the sensor is the slave. One master can communicate with multiple slaves. To configure the SDI-12 sensor: Click Devices in the left pane. In the Sites Tree pane, select the device with the SDI-12 sensor. Click the Configuration tab on the right pane. Expand the ADVANCED DEVICE CONFIGURATION tree, and then select Serial. Select the Channel, and then configure the following items:

1. Save the configuration changes, and then validate that the device rebooted by doing the following steps: Click Devices in the left pane, and then select the device in the Sites Tree pane. In the right pane, click the Commands tab. You will see a Reboot command after a few seconds. If no Reboot command is displayed, click Actions > Reboot in the Device Information pane to manually reboot the device. Both the configuration changes and the reboot will take effect after the device contacts the server. You can swipe the magnetic Activator key over the embossed logo on the face of the device to force a device reset, which can expedite the time for the device to connect to the server. APPENDIX SDI-12 Transaction without CRC The following table shows a typical transaction with no CRC and a just a few parameters:

All commands and responses are terminated with . means ASCII value of 13 (which is 0D in hex). means ASCII value of 10 (which is 0A in hex). These two bytes are "new line".

SDI-12 Transaction with CRC SDI-12 is designed to work even when the cable length between the logger and sensor is extremely long. When working on long cables, communication errors might happen. For example, bits might get flipped along the way. One way to detect this error is by adding a CRC code to the end of every response from the sensor. CRC stands for "cyclic redundancy check". It will not fix communication problems, but it will alert you that you have them. An SDI-12 master can instruct the slave to add a CRC code to every response. This is done by adding "C" to the "M" command. Example:

SDI-12 Transaction with Additional Measurements The following table shows SDI-12 capabilities per firmware version: