3654 Portable H2/N2 Analyzer - Operating Instructions 19 of 66
Operator Manual ORBISPHERE
2.2 Taking Measurements
To start the analyzer, press the POWER switch (located bottom left of the keyboard).
When you turn power on, the instrument displays the software version number briefly,
and then starts a series of start-up tests. This process should take only a few minutes,
during which time a [tSt] message is displayed on the LCD. Once the tests are
completed, a clearing message [---] is displayed for a further sixty seconds before the
instrument switches automatically to measurement mode.
Note:
The start-up tests will be repeated until successful, or for a maximum of 15 minutes. If
the tests are still unsuccessful after 15 minutes, a [Err] message will be displayed and
the instrument locked. Turn the instrument off and retry the start-up procedures, but if
the problem persists, please contact your local Hach Ultra service representative for
assistance.
Measurement updates are displayed every 20 seconds, and it is normal for the right-
most digits to vary in reaction to slight variations in gas content. For accurate
measurements, the sensor's membrane must be at the same temperature as the sample
to be analyzed. If this not the case, allow some sample to pass through the flow chamber
for about 3 minutes before taking any measurements.
Minimum sample flow rates, measurement ranges and response times for the various
membranes are given in the tables in “Sensor Specifications” on page56.
The LCD includes a right-side marker to distinguish between gas concentration
measurements and temperature. This marker also indicates the measurement display
units (k/kg, V/V, etc. depending on the instrument configuration).
To switch between gas measurement and temperature measurement, press the Up/
Down Arrow buttons. To illuminate the LCD for approximately three minutes, press the
Backlight button.

2.2.1 Select Gas Measurement Phase

Ensure the gas measurement phase is correct for this measurement. For details on
viewing the current setting, refer to “Reviewing Instrument Configuration” on page 29.
For details on changing this setting, refer to “Configuring the Instrument” on page29.

2.2.2 Measurement Mode

You can set the measurement mode to normal or maximum. For details on how to do this
refer to “Measurement Mode” on page 33.
Maximum mode facilitates making measurements in bottles and cans. To search for a
maximum measurement value, press the MEAS button.
• The LCD first shows the message [run] for a few seconds, before displaying
measurement values.
• After a 60 second measurement cycle, the instrument searches for two
consecutive gas measurements with less than 2% difference. When this condition
occurs, the displayed value freezes on the LCD (indicated by a blinking display),
allowing you to note down or store the data.
The display remains frozen until you press the MEAS button to make a new
measurement, or you select normal measurement mode (as described in “Measurement
Mode” on page 33).