Membrane 29561A is available for any gas measurement. Membranes 2935A and 2952A are
available for H
2
measurement only. Choose OK when the desired membrane is selected.
Note: Only those membranes applicable to your system can be selected. All other membranes are grayed out.
6.4.4 Automatic data acquisition - Setting sampling intervals
The instrument can perform as a standalone data acquisition device, automatically recording gas
measurements with the date and time, and storing up to 500 of these values. Choosing the Hach
3654 program's
Configuration
,
Sampling Rate
menu lets you select time intervals (acquisition rate)
for this storage capability.
Use the slide bar to view and select a sampling rate, from 15 seconds to 1 hour. The selected rate is
shown in the
Acquisition rate
window. Click
OK
to save this rate. Once your choice is made, the
instrument can be used independently of the Hach 3654 program for data acquisition. Refer to
Note: The Acquisition rate set via this menu is independent from the monitoring chart updating rate in
on page 17. The sampling rate menu applies only to automatic data acquisition, while
the chart updating rate is used only for displaying real-time results via the monitoring chart.
6.4.5 Calibration medium
You can use the
Configuration
,
Calibration medium
command to select how the sensor is to be
calibrated.
Choose either in pure H
2
or N
2
gas at atmospheric pressure or in a liquid or gaseous solution at a
known concentration of gas. Choose
OK
when the desired medium is selected.
Note: You can create a solution having a known H
2
or N
2
concentration by dissolving H
2
or N
2
in water at a
measured temperature and pressure. Hach Lange can provide equipment for generating such a solution.
Alternatively, you can analyze a carbonated beverage independently by other acceptable means.
6.4.6 Locking out the instrument’s CAL button
You can use the
Configuration
,
Sensor Calibration Status
menu to prevent an accidental sensor
recalibration from the instrument keyboard.
Choose
Disabled
to lock out the keyboard
CAL
button. To unlock this capability, choose
Enabled
.
Choose
OK
when the desired mode is selected.
6.4.7 Rolling average
Choose
Rolling Average Status
from the
Configuration
menu to enable or disable the averaging of
gas concentration measurements.
To enable averaging on three successive gas measurements, choose
Enable
. Choose
Disable
to
disable rolling average.
6.4.8 Automatic shutdown
Choose
Automatic Shutdown Status
from the
Configuration
menu to activate the Automatic
Shutdown feature.
If you select
Enable
, the instrument switches off automatically after 10 minutes of inactivity, thereby
economizing battery power.
6.4.9 Measurement mode
Choose
Measurement Mode
from the
Configuration
menu to enable maximum measurement
mode for sampling in bottles and cans.
In
Maximum measurement mode
, the instrument searches for two consecutive measurements with
less than a 2% difference, as also described in
on page 14. When this occurs,
the display is frozen and you may store the data. The instrument remains in this mode until you
select
Normal measurement mode
.
Section 7 Calibration
7.1 Barometric pressure sensor calibration
You must have access to an accurate barometer to calibrate the instrument's internal barometric
pressure sensor. This is done using the Hach 3654 program on the PC. Choose
Troubleshooting
,
Pressure Calibration
and a message will warn you that the current calibration will be lost.
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