Calibration Setup - Hach ORBISPHERE 3654 Manuel D'utilisation De Base

7.2.1 Calibration setup

Ensure that the purge gas is flowing at the recommended rate through the sensor by placing the
purge gas exit tubing into water. This rate should be more than four bubbles during the purge which
lasts for 4 seconds. This purge cycle is repeated every 20 seconds.
The procedure requires a source of pure gas (regulated by a pressure valve) connected to the
central entry port of the flow chamber, an accurate pressure gauge (better than ± 2%) at the exit of
the flow chamber, a needle valve to control the flow on exit, and a beaker of water to monitor the gas
flow. Refer to Figure 5.
Figure 5 Calibration setup diagram
1 Needle valve
2 Accurate pressure gauge
3 Flow chamber
7.2.2 Calibration at atmospheric pressure
The sensor can be calibrated in pure H
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. Refer to
the calibration medium to In measured pure gas at atmospheric pressure. Refer to
medium on page 20.
2. Connect a source of pure H
on page 22. 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. Refer to Locking out the instrument's CAL button
4. A 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
22 English
or N
2 2
Barometric pressure sensor calibration
or N gas to the inlet of the flow chamber. Refer to
2 2
4 Pressure valve
5 Beaker of water
6 Pure gas supply
gas at atmospheric pressure.
on page 21 before attempting this
Gas measurement phase
on page 20.
on page 19. Set
Calibration
Calibration setup