Taking Rain Measurements - Van Walt Rain Gauge Operating Instructions Manual

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VAN WALT

Monitoring your needs

4.2

Taking rain measurements

The datalogger records the number of

contacts made by the rain gauge and

converts those to the amount of rain

in mm. The datalogger has two ways

of processing these contacts. Channel

1 processes the number of contacts,

determines the amount of rain between

two samplings times and stores this value.

Channel 2 is a so-called integrator, that

keeps on recording as the new value,

the new value from channel 1, with the

previous measurement total added to it.

This is called the accumulation of data.

In order to measure the daily amount of rain (the most commonly used procedure) the Sample

speed of the data- logger is set at 24 hours in LDM e+, e-SENSE direct or on the e-SENSE data site. If

a lower Sample speed is selected, a so-called intensity measurement can be taken. Rain intensity

measurements are normally expressed in mm per

hour, and for these the Sample speed needs to be set at 1 hour. An even lower Sample speed

can be selected if the rain intensity needs to be recorded over shorter periods.

e+ Sensors possess an alarm function which activates the alarm status of the sensor when

measurement values exceed a certain pre- determined limit. A device that has been connected

can detect an active alarm status and depending on its function, can respond by performing a

specific task after which it can turn off the alarm status of the datalogger. The alarm function is set

by means of alarm boundaries and hysteresis limits. As soon as the measurement values exceed

one of the alarm boundaries the alarm status is activated.

The alarm status can be reactivated only once the hysteresis limits are reached. The limit values

can be set in LDM e+, but LDM e+ does not support alarm functionality. The relevant settings have

the following meanings:

• AlarmHigh: specifies the high limit that will cause the alarm status to be activated.

• HystHigh: specifies the high limit that will cause the alarm function to be reactivate.

• AlarmLow: specifies the low limit that will cause the alarm status to be activated.

• HystLow: specifies the low limit that will cause the alarm function to be reactivated. (note: the

low limits do not have any practical use when measuring rain)

Operating Instructions

Rain Gauge

Alarm High

Hysteresis

High

Alarmstatus

Externe

Heraktlvering

Ultschakeiing

Alarmfunktle

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