TURBO INSTRUCTIONS
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Power On Function
In order to save power, the power to the
sensing probe on the Turbo is normally
off, even when the Turbo sensor itself
is powered. The sensing probe requires
a warm-up or stabilization time before
returning valid readings. The sensing probe
is turned on when a reading is requested
or when a Power On command is written
to the Turbo.
(Note: If you are recording sessions, reading
with Aqua4Plus, or using SDI-12, you do not
need to be concerned with the stabilization
period. It is automatically taken care of
in these situations. You only need to be
concerned when using your own device to
take Modbus readings.)
There is a “power on” register on the
Turbo (register 62720 or 0xF500). When a
positive value “n” is written to this register,
the power is turned on to the sensing
probe and remains on for n/4 seconds.
When a reading is requested, the timer
is reset and the sensing element remains
on for another n/4 seconds. To force the
power off immediately after a reading, for
power savings, write a zero to the register.
If the power to the entire Turbo sensor is
turned off, this value defaults to 48 (or 12
seconds).
The recommended procedure to ensure
proper warm-up/stabilization and to
conserve power is:
• Write Power On value of 48 (48/4 =
12 seconds)
• Power turns on
• Starts sampling about two times
per second
• Wait 10 seconds then request a
reading
• Returns most recent sample
• Resets Power On value to 48
(48/4 = 12 seconds)
• Write Power On value of 0 (zero)
•
Turns power off
• Retains last reading
If you Cannot Write to the Power On
Register
If you are reading your device using a meter
or other device that cannot write the Power
On but simply takes readings on a specified
schedule, be sure to set the polling interval
to less than 12 seconds. This will ensure
that the sensing probe is always powered
up and readings should be fresh and stable.
Note that the first reading when you turn
on the sensor and meter will be old but will
refresh within a second or two.
For further information and detailed
Modbus examples, refer to our website at
www.seametrics.com.
Data Format
The data is returned as 32-bit IEEE floating-
point values, high word first, also referred
to as big-endian or float inverse.
Wiper
Before each reading, the sensor will apply
power to the turbidity sensing unit and
run the wiper once. If your polling interval
is 10 seconds or less, the sensing unit will
remain on and will only wipe once when
first started.
APPENDIX C: READING THE SENSOR
