Campbell Scientific PVS4100/4120/4150 Portable Automatic Samplers - Manual (Page 9)

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Section 1. Product Overview
1.1 Introduction
The PVS4100, PVS4120 and PVS4150 Portable Samplers are automatic liquid
samplers for water and wastewater applications. PVS Samplers are capable of
gathering fluid automatically from a variety of sources, including containers,
open channels, sewers, pipes, and any open source of water.
Samplers are designed for reliable unattended sample collection. Portable units
are capable of keeping the temperature of the deposited liquid at 4ºC (39.2ºF)
for up to 24 hours using crushed ice or ice packs until the samples are gathered
and brought back to the laboratory for analysis.
There are a variety of methods for depositing samples. Composite sampling is
used where samples are deposited, over time, into one container. Discrete
systems are used when multiple bottles are needed. These are also called
“sequential” systems, and involve a stepper with distributor arm which
dispenses the liquid into a bottle, then moves to the next bottle.
Operating temperature for portable samplers is 10ºC to 50ºC (50ºF to 122ºF),
adaptable down to 0ºC (32ºF) upon request.
Samples can be triggered by a variety of means. The internal clock on the
controller can be set to sample based on time/day (e.g. sample every hour).
There are also a variety of external inputs that can be connected to control
sampling using the optional external signal cable. Pulse count is useful for
sampling after a certain number of pulses have been reached (e.g. using a rain
gauge to trigger sampling). The 4-20 mA option is useful for flow-based
sampling (e.g. using a flow meter to trigger sampling after a certain volume of
water has passed by). External contact is used to control the sampler from
another data logger or PLC, and is useful when full external control is desired.
Level control is the option to choose when the application has starts and stops
(e.g. using a float switch to trigger sampling when water is present, then stop
sampling when the water drops below the set level).
When sampling is initiated, liquid travels through the intake tube into the
metering chamber. The amount of water taken is set mechanically using the
liquid sensing rod and the volume control tube, which means sample accuracy
is precise every time, usually within +/- 2% or +/- 2ml.
Once the pre-set amount has been reached, all excess liquid is purged from the
system, and the sample is dropped into a container. Sample containers range
from 500 ml (500 cc or 2 cup) wedges in discrete systems, to 9 liters (2.3
Gallon) containers for composite systems.
Intake tube is offered in either 3/8” (9.5 mm) ID or 5/8” (15.9 mm) ID, and can
be either Nylon-reinforced PVC or Teflon-lined PVC. Transport velocity varies
depending on height and distance being sampled. For most situations the
sampler pulls at over 1.5 m/s (5 ft/sec). For an in-depth speed chart, refer to
Section 1.3.7 Sample Transport Velocity
on page 1-15.