Hach ORBISPHERE 3658 Basic User Manual page 19

3. A brief clearing [---] message appears.
4. Press CAL again within a 3 second period. The instrument then displays the concentration of
CO based on the last value of the calibration coefficient.
2
5. Modify this reading using the Up/Down Arrow keys until the displayed concentration agrees with
that of the calibration solution.
6. Press CAL again.
7. Start the flow of the standard (calibration) solution through the flow chamber. Adjust the flow until
the liquid is foam-free. The flow rate should be a minimum of 150 mL/min. (50% on the
32311 Flow Meter) and stable.
If the instrument makes two consecutive measurements with less than 1% difference, it calibrates
against this stabilized value. The LCD then displays the message [CAL] to indicate calibration
has been successfully completed.
If the calibration does not complete, the LCD displays the message [Err]. The reason for this
calibration error is either that the measured gas partial pressure is under 5 mbar, or that a wrong
instrument key was pressed during the calibration steps.
Note: A flow rate lower that 150 mL/min can be used for the calibration, but you must ensure that all
measurements made after the calibration are made at exactly the same flow rate as that used for the
calibration. For accurate results it is recommended to use a model 32311 Flow Meter set at 50% for the
optimum flow rate of 150mL/min. at room temperature (25°C).
Calibration in CO
2
The sensor can be calibrated in pure CO
To ensure that the flow chamber and sensor components are dry, remove and blow dry the flow
chamber. Dry the sensor head surface with a clean soft tissue.
The analyzer uses an internal barometric pressure sensor during this calibration. First check that the
pressure sensor is correct and does not need recalibrating. If it does need to be recalibrated then
follow the instructions in
calibration.
1. Set the gas measurement phase to Gaseous (see
the calibration medium to In measured pure gas at atmospheric pressure (see
medium on page 16).
2. Connect a source of pure CO
on page 18, and adjust the gas flow to one bubble per second when the exit tube is immersed in
water.
3. Press the CAL button. Remember, this button may have been locked out to prevent an accidental
reset (see Locking out the instrument's CAL button
4. brief clearing message [---] appears.
5. Press CAL again within a 3 second period.
If the instrument makes two consecutive measurements with less than 1% difference, it calibrates
against this stabilized value. The LCD then displays the message [CAL] to indicate calibration
has been successfully completed
If the calibration does not complete, the LCD displays the message [Err]. The reason for this
calibration error is either that the measured gas partial pressure is under 5 mbar, or that a wrong
instrument key was pressed during the calibration steps.
Calibration in CO
2
The sensor can be calibrated in pure CO
accurate pressure gauge connected to the exit of the flow chamber.
When calibrating in gas phase, the flow chamber and sensor head must be dry. To ensure that the
flow chamber and sensor components are dry, remove and dry them with a clean soft tissue.
at atmospheric pressure
gas at atmospheric pressure.
2
Barometric pressure sensor calibration
gas to the inlet of the flow chamber, as illustrated in
2
at elevated pressure
gas at an elevated pressure. This method requires an
2
on page 17 before attempting this
Gas measurement phase
on page 16).
on page 15) and set
Calibration
Figure 3
English 19