Campbell Scientific OBS500 Smart Turbidity Meter with ClearSensor Technology - Manual (Page 32)

OBS500 Smart Turbidity Meter with ClearSensor™ Technology
For CR10X and CR510 standard mixed-array dataloggers, the datalogger
telecommunications command to enter SDI-12 transparent mode is nX
where n is the control port being used for SDI-12. For example, if the selected
control port is C1, the command would be 1X. In response, the
datalogger opens the link to control port 1 and responds with a prompt.
CR10X and CR510 dataloggers reply with “entering SDI-12”.
CR10X-PB and CR510-PB dataloggers require *#n being entered at the
prompt, where n is the control port being used.
Now check for a response from the sensor with address zero by typing the SDI-
12 identify command 0I! (that’s a zero, not the letter O). The sensor
should respond with an identification string similar to
013CSI.Std.01_xxxxxxxx, where xxxxxxxx represents the eight-digit serial
number. Note that the SDI-12 standard allows for multiple probes to be
connected to one datalogger control port. For example, if you have another
SDI-12 probe on C1 that has address 7, you could issue the identify command
7I!.
Only one sensor of the same address can be connected when using the change
address command.
7.4.2 RS-232
RS-232 measurements of the OBS500 are typically made by a CR800, CR850,
CR1000, or CR3000 datalogger or an RTU device. The OBS500 field cable is
used and wired appropriately for the measurement device. See TABLE 7-8 for
settings.
TABLE 7-8. RS-232 Settings
Bits per second 9600
Data bits 8
Parity None
Stop bits 1
Flow control None
Measurement commands are the same for RS-232 and SDI-12 as shown in
TABLE 7-7.
7.5 Calibration
7.5.1 Turbidity
Field recalibration is not recommended and usually not needed until the
OBS500 is sent back to Campbell Scientific for the two year service. We
recommend checking the calibration in the field as described below. If a
9-point calibration is needed, the OBS500 should be sent to Campbell
Scientific to perform the calibration.
The normalized response of an OBS500 sensor to SDVB turbidity over the
range from 0 to 4,000 TU is shown in FIGURE 7-5. As shown on the inset, the
response function is contained within region A, the linear region, of the
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