LISST-Holo2
User’s Guide
49
9
FAQs
What is a hologram?
Fundamentally, holograms are 3-D images that have first been projected, and then stored on a 2-D
surface. In the type of holograms captured by the LISST-Holo2 (so-called in-line holograms), a laser
beam is emitted and a small part of it is being scattered by the particles in the water. The part of the
laser beam that is not being scattered by particles interferes with the scattered light. This creates an
interference pattern - a hologram. The interference pattern is captured by a small digital camera.
Upon processing of the captured interference pattern (i.e. the hologram), it is possible to recover the
original image that created the hologram. Thus, the LISST-Holo2 does NOT capture and store an
image of the suspended particles. It is the hologram of the particles that is stored. During data
processing, the image of the suspended particles is reconstructed from the hologram. Subsequently
standard image processing methods can then be applied to get information about particle shape,
size, area, etc.
I connected to the
LISST-Holo2 with my
web browser, but now
it says “500 – Internal
Server Error”, or it
doesn’t respond at all.
Most likely this is because the LISST-Holo2 is asleep, or is busy collecting holograms. If the indicator
light on the end cap is rapidly flashing, it is sampling; set the switch lever to 0 to stop it.
If the light is dark, it is asleep; try toggling the switch lever from 0 to 1 and back.
If the LISST-
Holo2’s indicator is flashing green every 5 seconds, it should be ready to communicate.
Check the connections to your network.
How do I wake the
LISST-Holo2 when it is
asleep?
Toggle the white switch lever from 0 to 1 and back. That will wake it without starting logging. If you
leave the switch in the 1 position, the logging program will start.
Toggling the switch
didn’t work. Why not?
What now?
When the internal batteries are very low on charge, too low even to boot up, the LISST-Holo2 will go
into deep sleep. To wake from deep sleep, you must apply external power, either from the battery
charger (through the 6-pin connector) or the separate power supply (through the 5-pin).
The LISST-Holo2 went
to sleep while I was
offloading files. How
do I fix that?
Go to the Tools page and look for Automatic Sleep. Check the box that disables automatic sleep,
and click the Apply button.
Why can't the LISST-
Holo2 be used when
the flow speed is more
than 2 m/s?
It takes 2 microseconds to capture the hologram using the digital camera. The image captured by
any digital camera is made up by a large number of pixels. If the particles in the water move more
than one pixel during the time it takes to capture and store the hologram, the quality of the
reconstruction images will be affected. For the pixel size used in the LISST-Holo2, a flow speed of
more than 2 m/s will begin to blur the hologram. Consequently, if the LISST-Holo2 is used on a
profiling platform, e.g. a CTD, the profiling speed must be 2 m/s or less. Likewise, if the LISST-Holo2
is deployed on a mooring or tripod, the current velocity around the instrument must be less than 2
m/s.
Why should I connect
the LISST-Holo2 to the
Internet?
Connecting the LISST-Holo2 to a local area network that is connected to the Internet has benefits.
The first benefit is that the instrument is accessible from different locations across the network.
Connecting the instrument to the Internet has other advantages such as checking for firmware
updates, syncing the time with international standards, and transmitting log files to Sequoia. It is not
necessary to have the instrument connected to a network or the Internet but it can be useful when
needed.
How do I connect the
LISST-Holo2 to the
Internet?
The LISST-Holo2 comes configured with a pre-selected IP address, netmask, gateway, DNS 1, and
DNS 2. These settings will work with the provided wireless router but they will probably not work with
your existing local area network. Because the LISST-Holo2 requires a static IP address, an IP
address must be selected so as not to interfere with other computers on your network. It is highly
recommended that users work with their network administrators to determine the proper settings for
their network. The new value can be entered on the Tools page (see section 8.3). Be sure to double
check the values before pressing the Apply button on the Tools page. Once the Apply button is
clicked the IP address will change immediately and you will need to log into the new IP address
before communication can be re-established. If incorrect values are entered it is possible to change
them manually through serial port communication. Contact Sequoia for details of this procedure.
Does the LISST-Holo2
support DHCP?
No. The LISST-Holo2 does not support DHCP (Dynamic Host Configuration Protocol).
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