Campbell PVS5120 Series, Инструкция по эксплуатации

Страница: 33 / 102

PVS5120-Series Portable Samplers
21
7.2.2 Liquid Sensing/Conductivity Rod
This probe, also called the liquid sensing rod or conductivity rod, is used to
stop the sample intake. Always ensure that its lower end is located above the
volume control tube and below the bottom of the float valve barrier (plastic
ball). Because the fluid intake is always turbulent, there must be at least a 1/2
inch difference between the rods. If you have a variable height water source
that may be dry at times (like a storm water application), you may want to
increase the offset to at least an inch between the volume control tube and the
conductivity rod.
In applications with substantial oil or grease, the rod can become coated and
lose its conductivity. This is prevented by cleaning the rod regularly. In
extreme cases, extra stainless steel wire can be wrapped around the liquid
sensing rod to increase its surface area.
The liquid sensing rod and volume control tube must be kept
clean to ensure the conductivity necessary to detect the
presence of the fluid.
7.2.3 Cables
7.2.3.1 PVS5120CBL-L Control Cable (pn # 30432)
The PVS5120CBL-L control cable connects the sampler to a datalogger,
MD485, or another external device that will control or monitor the sampler
(FIGURE 7-5 ). The cable has a connector at one end that attaches to the
Signals connector on the Control Panel. The other end of the cable has pigtails
that connect to the external device.
7.2.3.1.1 Wiring
FIGURE 7-5. PVS5120CBL-L Control Cable (pn # 30432)
When using SDI-12, the sampler connects directly to the datalogger. When
using PakBus® or Modbus®, the sampler connects to an MD485 and the
MD485 connects to the datalogger using an SC12 cable or # 18663 null modem
cable (see MD485 manual for more information). The optional water
detection probe connects to the gr
e
y and yellow wires on the PVS5120CBL
control cable. TABLE 7-1 is a general wiring table.
Only connect the wires needed for the specific control type.
Cap, tape, or cut the unused wires at the shield. Connecting
the unused wires to ground causes problems with the
fault/red wire. Allowing the unused wires to touch can cause
shorts.
CAUTION
CAUTION