EML ARG100 User Manual - page 9
UM-780-400-SBS Manual – V2.00
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4.Wiring Guidelines
This section gives information on the wiring of ARG100 rain gauge.
For most applications, the rain gauge may be connected directly to a pulse counting input (contact
closure) on a data logger, but some care is needed if long cables are used. In a long cable significant
capacitance can exist between the conductors, which discharges across the reed switch as it closes.
As well as shortening the life of the switch, a voltage transient may be induced in any other wires
which run close to the rain gauge cable each time the rain gauges tips. To help this situation, 100
resistors are pre-fitted to each of the reed switches (Figure 3), these will help protect the switches
from arcing and help prevent transients.
Figure 3 - Reed switch and resistor
NOTE: The type of measurement is contact closure (switch), therefore it does not matter which way
round the wires from the logger or counter are connected.
ARG100/STD rain gauge
This is the standard version of the rain gauge which is supplied with two short lengths of wire
approximately 220mm. The series resister shown in Figure 3 is inserted in one wire and covered by
adhesive type heatshrink sleeving.
ARG100/EC rain gauge
The ARG100/EC is supplied fitted with a 6-metre extension cable. One wire is attached to the resistor
and covered with adhesive type heatshrink. The other wire is attached, covered with heatshrink and
the entire joint covered again with heatshrink. The cable passes through a grommet in the outer base.
The cable length may be shortened or lengthened as required. If the cable is lengthened, please ensure
a good quality environmental connector, or a heatshrink joint similar to the one described previously,
is used. Extension cables used must be of a similar specification.
ARG100/STD rain gauge with Limpet XL datalogger
If the ARG100 rain gauge is ordered with an EML Limpet XL datalogger and accessories, a specific
connector will automatically be fitted that is compatible with the logger.