EIJKELKAMP Scuba, Руководство пользователя

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ISE calibration is more complex than calibrations for most other sensors, but we’ve made it as simple as possible in
Calibrating Ion-Selective Electrodes: The difference between activity and concentration. This document can be found on
the Eijkelkamp flash drive.
4.16 Total Dissolved Gas (TDG)
The TDG sensor is a pressure transducer (the same one used for the 10-meter
depth sensor) attached to a “membrane”. This membrane is a long piece of
thin-wall, silicone tubing whose job is matching gas partial pressures inside
the tube with those of the surrounding water. The sum of those partial
pressures is measured by the transducer, and that’s the TDG of the water.
Aside from keeping the membrane as clean as possible without tearing the
tubing, the TDG sensor requires no maintenance. When the membrane is torn or is just too dirty, the membrane
assembly must be replaced. Simply unscrew the old membrane and screw on a new membrane. Screw it on finger-tight,
plus 1/4 turn.
Silicone rubber is chosen for the membrane material because gases pass through silicone readily. This means that
response time for silicone is much faster than if the membrane were, say, Teflon. However, if the membrane is soaked in
water for more than a few hours, the silicone absorbs just enough water to slow the gas transfer considerably. This is not
usually a problem for unattended monitoring applications (the TDG doesn’t change very quickly anyway) but can be
annoying if you are doing daily spot-checks. In that case, it’s best to dry out the membrane between stations by using
only a few drops of water in the storage cup instead of a few ounces.
4.17 PAR
The PAR (Photosynthetically Active Radiation) sensor measures the amount of light available to biota for photosynthesis.
It’s units of measurement are micro-moles of photons per square meter per second, or photon μ moles/m 2 second. This is
also referred to as micro-Einsteins per square meter per second.
The sensor looks like a light bulb and receives light from all directions except the “blind spot” at its base. Eijkelkamp
mounts the PAR sensor a few inches away from the multiprobe, facing away from the multiprobe, so that the
multiprobe is in the blind spot.
PAR sensors are supplied with a dummy plug so that you can use the Scuba 2 without the
PAR sensor attached.
PAR measurement is accessed for display through the menu structure just like all other
sensors. The PAR sensor is calibrated at the LI-COR factory, and cannot be calibrated by
the user. LI-COR recommends that the sensor be returned to the factory every couple of
years to be re-calibrated.
PAR sensors are not attached to the multiprobe when shipped from Eijkelkamp; there is a
dummy plug in the PAR port. To attach the PAR sensor, simply unscrew the dummy plug’s
locking sleeve (it’s the same type locking sleeve used for Eijkelkamp cables) and pull the
dummy plug out of the port. Slide the locking sleeve onto the non-light-bulb end of the
PAR sensor and push the PAR sensor into the port as you tighten the locking sleeve. This
may take a little bit of practice, as the locking sleeve’s off-center hole has to shift slightly
to center of the PAR sensor and its port.
Scuba top cap
PAR port
Locking sleeve
PAR sensor