Atmospheric Pressure Equilibrium; Sensor Installation; Purge Gas Connection - Hach ORBISPHERE 3654 User Manual

Installation

3.3 Atmospheric pressure equilibrium

As soon as you receive the instrument, it will be necessary to ensure the interior and exterior of
the instrument are both at the same atmospheric pressure. It is probable that during shipment
these pressures will become different.
To ensure the pressures are equal, simply press the relief valve switch located on the top of the
instrument (refer to

3.4 Sensor installation

The TC sensor connects to the instrument base through a 10-pin LEMO connector. A locking
pin holds the sensor in place.
Figure 2 TC sensor - exploded view
1
2
3
Both the membrane-covered TC sensor and the flow chamber are shipped pre-installed on the
instrument. It will, however, be necessary to remove the flow chamber when servicing the
sensor. Refer to

3.5 Purge gas connection

It is critical that the TC sensor has a supply of purge gas running before operating the system.
The TC sensor, when exposed to a liquid sample, will become damaged if the purge gas is not
running. CO
cylinder located at the bottom of the instrument supplies the purge gas. This cylinder is
refillable. Refer to
The TC sensor is purged cyclically. In measurement mode, a cycle consists of a 4 second purge
followed by 16 seconds of measurement. When the instrument is in standby, the purge time is
the same, followed by a 17 minute delay. During the purge time, the flow rate varies, depending
on the pressure inside the cylinder. At least four bubbles should exit from the purge gas exit
during the purge time.
The purge gas input to the sensor uses a Tygon tube (4 mm outside/2 mm inside diameter,
110 mm long) that attaches to the base of the sensor. Refer to the exploded sensor diagram in
Figure 2
The hole in the side and near the base of the sensor is the purge gas exit. To check the purge
gas flow rate, push the supplied nylon tubing into this hole, to its limit. To disconnect it again,
press on the ring surrounding the tube and pull out.
10
4 on page
5
Purge gas (air) inlet
Output connection to portable instrument
Purge gas (air) outlet
Sensor maintenance on page 39
is used to purge the N
2
Purge gas cylinder refill on page
above.
9) and hold it down for about 5 seconds before releasing.
4
4 External temperature sensor
5 Storage cap
for detailed information.
sensor and N or CO
2 2
43.
3
is used to purge the H
2 2
1
2
sensor. A