BS 7843-3.2:2005 pdf free.Guide to the acquisition and management of meteorological precipitation data —Specification for raingauges—Section Tipping bucket raingauge.
BS 7843-3.2 This British Standard specifies the minimum performance requirements for any ground mounted tippingbucket raingauge(TBR).It does not specify any physical shape or dimension unless these are necessary tomeet the performance requirements.
NOTE Recent R & D suggest that aerodynamically shaped gauges achieve a catch more similar to check gauges than do cylindershaped gauges.
A tipping action is generated by the weight of the precipitation (rainfall depth) exceeding the calibratedbalance which causes the bucket assembly to rapidly tip over, emptying the bucket. Figure la) andFigure 1b) illustrate the tipping system.Figure 2 illustrates the arrangement of a typical TBR.
Precise measurement is achieved by adjusting the height of the calibration adjuster, a post that the bucketassembly sits on when it is at rest. Increasing the height allows the respective bucket to hold a smallervolume of water before the point of balance is exceeded.Similarly, reducing the height of the adjusterallows the respective bucket to hold a greater volume of water before the point of balance is exceeded.Electronic sensors such as magnet and magnetic switches, optical interruption sensors or other non-intrusive means normally detect the action of the “tipping” event.
Raingauges shall be calibrated to±2 % or better, using the calibration process as specified in Annex A.NOTEThis tolerance is based upon all potential effects that can affect the measurement (temperature, humidity etc.)
As bucket assemblies contain two buckets, the maximum variation permitted between each bucket, basedupon the volume of one bucket compared with the other, shall be 2 %.
NOTEThis is irrespective of the actual calibrated volume achieved.
Standard tip event sizes shall be either 0.2 mm/tip or 0.5 mm/tip. The precise volume required to achievethe tip event may be calculated using the formulae described in A.2.3.
NOTEThe effect of bucket size is well documented.Small resolutions provide finer resolution and a clear indication of trends buthave high accumulative errors. Large buckets provide more accurate totals but the coarse resolution provides poor trend data.BS 7843-3.2 pdf download.