Starting SDI-12 Network Communications

To activate the SDI-12 output port on the VibWire-108-SDI12. the serial output port has to be assigned for data communications. This operation is the same for the SDI-12, RS485 and TRs24 models.

In order that the sensor data is correctly identified each instrument upon a network has to have a unique identifier address assigned. For SDI-12 networks this ID number is an integer 0-10. For RS485 networks the ID is an integer in the range 0 - 255.

1. Starting at

2. Select “Menu In” button

3. Use the Up & Down Keys to select the option “SERAL”

“Analg C0d C1d C2d C3d C4d C5d C6d C7d” are the other options available

Once the “SERAL” output is selected the “Menu Out” key has to be pressed to confirm this option.

4. The VW-108 will return to the display

and now the SDI-12 port for the instrument is now activated.

Using SDI-12 Commands with the DT80

The DT80's use the SDI12SEND command allows to manually send SDI-12 commands to the VibWire-108 for testing and
configuration purposes.

The format of this command is as follows: SDI12SEND channel "string"     where:

channel   is the digital I/O channel (5 – 8) (4 for DT81)
string      is a valid SDI-12 command string to send to the device. All commands start with the sensor address (0 – 9) and end with
  a ! character.

If there is a reply from the device then it will be displayed, assuming the /M (enable messages) and /h (free format) switches
are set. For example, the aI! command (a = address) should result in the sensor returning an identification string, eg.

SDI12SEND 5 "0I!"     -- send out ID request for instrument attached port 5D.

5SDI12: 0I      !a13KEYNESCOVibWire-1080001\r\n Part Description assigned by Keynes

Example - Measure on Demand Application

In this example the documentation for a hypothetical stand-alone geotechnical instrument system states “send the aC1! (or aM1!) command to measure (1) strain - Frequency Hz (2) displacement - Frequency Hz (3) Pressure - Frequency Hz (4) temperature - Frequency Hz (5) sensor temperature - mV (6) sensor temperature - mV (7) Current loop - Volts (8) Current loop - volts for an instrument with ID number of 6 and connected to the DT80 using digital I/O 7D.

In this application we are looking at a VibWire-108 configured to use 4 vibrating wire sensors with two of these sensors having the temperature compensation sensor being monitored and 2 current loop input signals being recorded from the analogue input channels.

In order to make the VibWire-108 report values it first must complete a scan of all channels. To force the VibWire-108 to scan the input sensors issue the command

BEGIN “Getdata” -- this program runs repeatedly for 2 min samples

RA2M 7SDI12(AD6, R101,” Displacement Hz”)

7SDI12 (AD6,R202, “Temp mV”)

7SDI12 (AD6,R204, “Loop value - mV”)

LOGON

END

Note The VibWire-108 supports both the aMn! and the newer aCn! SDI-12 commands then be sure to refer to the section on the aCn! DT80 manual command in the logger documentation when determining which register numbers to use. These two SDI-12 commands do the same thing but the timing constraints for the operation of the command may be different. The DT80 always uses the aCn! command in preference to aMn!.