YSI 5200 - Manual (Page 52)

YSI Incorporated 50 5200 Recirculating System Monitor
Calibration
Calibration is covered in Section 6 Calibration. pH can be calibrated at either one point or two points. See
Section 6.2.4 pH Calibration for details.
Set Point Menu
The YSI 5200 can control pH by dosing a buffer solution , injecting CO
2
gas or both. pH control can
operate in two different ways. It can operate the same as most other 5200 control systems—when the
parameter value reaches the low or high range setpoint, control is activated until the value returns to the
optimal setpoint. Or, it can operate in a timed mode—when the value reaches the low or high range
setpoint, control is activated for a fixed length of time (Dose Time) regardless of whether or not the value
returns to the optimal set point. The 5200 then waits for a fixed length of time (Dose Wait) before
checking the value of the parameter and applying additional control. The default method of pH control is
the timed mode. To select the normal mode, set the Dose Time to 0.
When using timed mode, additional values must be entered on the Set Points Menu, including the dose
and dwell (Dose Wait) values. The dose time allows you to establish the length of time a dose is
administered and the dwell time allows for a period between doses to prevent over-applying a dose.
SetPoint
The pH Set Point defines the optimum pH level that you wish the YSI 5200 to maintain in the aquatic
environment. See Section 5.3.1 Entering Setpoint and Range Values for an overview of control functions.
Dose Up
Dose Up in minutes (time per dose of buffer solution) is the amount of time that the YSI 5200 will dose
buffer to bring the pH level back up into the target operating range to the optimal Set Point. The
acceptable values for buffer solution dosing are from 1 to 999 minutes. Set to 0 to select normal pH
control (see Section 5.3.4 pH System, Set Point Menu).
Dose Up Wait
Dose Up Wait (dwell time) is the length of time that the YSI 5200 will wait until dosing can occur again.
This feature prevents overdosing a system with buffer.
Dose Down
Dose Down (in seconds) controls how long the CO
2
gas valve will remain open. The possible values
range from 0 to 999 seconds. For example, if you enter 10 seconds, when the upper end of the target
operating range for pH is reached, the YSI 5200 will turn on the CO
2
gas for 10 seconds to reduce the pH
to a lower value. A CO
2
Dose Down Wait time will force the YSI 5200 to wait to allow the gas to be
absorbed into the water. This will prevent the pH value from dropping too fast.
Set the Dose Down to 0 to select normal pH control (see Section 5.3.4, pH System, Set Point Menu) where
the YSI 5200 will turn the gas valve on when the pH level reaches the high end of the target operating
range and will keep the valve open until the pH drops below the optimal pH level. The 0 seconds option is
for systems with pressurized CO
2
injection.
WARNING: If the 5200 is instructed (by AquaManager) to transmit logged data during the Dose Down
cycle, dose time will be extended until data transmission is complete (up to 3½ minutes maximum with a
full data log).
Dose Down Wait
Dose Down Wait time is the time that the YSI 5200 waits before allowing another CO
2
gas injection to
occur. This time is selectable from 0-999 minutes. If the YSI 5200 senses that the pH is outside of the