Vaisala MAWS201 User's Guide download pdf (Page 145)

Chapter 5 _______________________________________________________________Maintenance

VAISALA _______________________________________________________________________ 143

consuming. In any case, it is virtually impossible to get the

adjustments absolutely correct, and it is generally preferable to adjust

the settings as closely as is reasonably practical, and then derive a

calibration factor for each rain gauge individually after dynamic

calibration.

Dynamic Calibration

1. Configure the gauge as shown in Figure 118 below or Figure

119 on page 144 (the latter setup will give a preferable constant

flow rate), ensure the gauge is leveled and connected to a data

logger or counter.

2. Fill a container with 1000 cm

of water for 0.2 mm/tip

calibration. This is usually achieved most precisely and

consistently by weighing the water on a balance capable of

measuring to 0.1 g (0.1 cm

). An alternative is to use a good

quality graduated measuring cylinder.

3. Allow the water to drip slowly into the gauge, taking at least 60

minutes to empty (approximately 40 seconds for each tip). At

the end of this period approximately 98 tips will have occurred.

The exact number is obtained from the data logger or counter.

To this, add on an accurate estimation of what fraction of a tip is

left in the bucket when the water stops flowing (a graduated

syringe is ideal for this).

WATER IN OPEN

TOP CONTAINER

FLOW

ADJUSTMENT

LEVEL GAUGE

BY USING

ADJUSTING SCREWS

SINK

9901-032

Figure 118 Dynamic Calibration

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Vaisala MAWS201 User's Guide Page 145