How many different transmitting stations will the vantage pro display console receive?

The Vantage Pro Console/Receiver can receive data from up to 8 transmitting stations in total. The maximum number for each individual type of transmitter is shown below:

TRANSMITTING STATION MAXIMUM #

Integrated Sensor Suite from Wireless Vantage Pro Station: max = 1

Anemometer Transmitter Kit (see note # 1): max = 1

Leaf Wetness/ Temperature Station (see note # 2): max = 1

Soil Moisture/ Temperature Station (see note # 3): max = 1

Temperature Station: max = 8

Temperature/ Humidity Station: max = 8

Note 1: You can only have one anemometer reading on the Vantage Pro: Either one from the ISS or one from the Anemometer transmitter Kit.

Note 2: Each Leaf Wetness/ Temperature Station can have up to 2Leaf Wetness sensors and up to 3 Temperature sensors.

Note 3: Each Soil Moisture/ Temperature Station can have up to 4 Soil Moisture Sensors and Up to 4 Temperature Sensors.

Can I mount the sensors away from each other?

On the Standard ISS the only sensor that can be moved away from the suite is the anemometer. It comes with 40ft of cable in case you want to get it up higher or to a space with better clearance. You may extend this longer by order more extension cable. You can also use the Anemometer Transmitter Kit to move it even further away.

How do I install the anemometer so the wind vane is oriented correctly?

If you mount the anemometer so that the arm points north, the wind vane will be ready for use immediately.

If you want to mount the anemometer such that it aims in a direction other than north you will have to recalibrate the wind direction from the Vantage Pro Display Console. See "CAN I CALIBRATE OR FINE TUNE MY WEATHER READINGS?" above.

Or you can recalibrate it from the vane itself, remove the vane by loosening the Allen set screw and lifting the vane off. Move the shaft so the pointer on the compass rose on the Vantage Pro Display Console points in the same direction that the anemometer is pointing. Place the vane back on so it is also pointing in that direction and then tighten the Allen set screw.

My wind vane and display console will not show 180 degrees.

That is correct. It turns out that we have 255 bits to sense 360 directions. Therefore our wind direction resolution is 1.4 degrees (360 divided by 255). Really that is not so bad because one degree is very small and also the accuracy rate of the wind direction is + or - 7 degrees.

How can I check the accuracy of the rain gauge?

It is not uncommon to notice that the the rainfall recorded by your VP station may be significantly different from that reported by other weather monitoring stations in your locality or region. There may be several reasons for this:

First, rainfall can and does vary significantly even over quite small areas and especially during more localised rainfall events such as thunderstorms. So differences in reported rainfall can often be genuine.

Second, it's important to remember that reporting periods do vary between stations. In the UK, for example, it's common for the 24-hour period of 0900-0900 to be used for manual observations and readings will therefore often not agree with a 2400-2400 period used by default for an automatic station.

Third, the rain gauge site must be fully exposed to rainfall. Any, even minor, shortfall in achieving optimum exposure can lead to significant under-recording of rain. Many urban/suburban locations simply cannot achieve the wide-open exposure that's necessary to record maximum rainfall and this will be another common reason for significant differences in rainfall readings.

Fourth, it is important to clean the raingauge at least every few months and if you're seeing suspiciously low or slow readings, then do check the cleanliness of the gauge as a first step. A surprising amount of general dust and detritus can enter the raingauge funnel and slow (and ultimately block) rainfall passing through the central hole. The little mesh circle supplied with every VP gauge will help to keep this hole clear if properly installed and firmly attached. Remember also that if the temperature is at or around zero then residual rain or dew may have frozen and blocked the funnel. Subsequent rain or snowfall will obviously not be measureable until the snow/ice has melted (unless of course you have a raingauge heater).

But if the factors above can be ruled out then attention will naturally turn to the accuracy of the gauge itself. There are two methods for checking accuracy, described below, but first some preliminary points:

The VP ISS must be installed such that the rain collector cone is absolutely level in order to allow the tipping bucket mechanism to function correctly. Check this using a bubble level placed on the rain cone aperture. The ISS should also be mounted securely (and separately from the anemometer) with the rain gauge at a height of a few feet (eg 4 feet - 1200mm) above the ground. This proximity to ground level will reduce reduce both the general erratic recording of rainfall in high winds and that due to winds swirling around obstacles such as roof structures etc and also any mechanically-induced errors due to the raingauge wobbling in high winds.

Correct operation of the the rain collector buckets can be tested by tipping the bucket slowly by hand (2-3 seconds per tip or slower - the sensing mechanism ignores tips that occur too fast) and checking the result on the console display. Thus twenty tips at a measured pace should increment the rainfall reading by 20 x 0.01" = 0.20" with a metric equivalent of ~5.0mm.

Note that the raingauge has limited acuracy for small amounts of rainfall and there is absolutely no point in using isolated short showers of rain to monitor accuracy. Also, during extremely heavy rain (>2"/hr or 50mm/hr) it is impossible for the tipping bucket mechanism to keep up 100% with the flow of rain and small losses will start to occur. The general accuracy of the raingauge is as follows:

For rain rates up to 2"/hr (50mm/hr) accuracy is specified at ±4% of total or ±1 bucket-tip, whichever is greater. From rates from 2"/hr to 4"/hr, the figure is ±5% or ±1 bucket-tip, whichever is greater. (The ±1 bucket-tip qualification is necessary, because this is the limit of resolution of the tipping bucket mechanism - either the bucket tips or it doesn't, hence the smallest unit of rainfall is effectively one bucket-tip.) If the rainfall total was small enough that one bucket-tip was greater than 4% of the total, then the 4% accuracy level could not logically be applied. Thus for moderate rain rates the accuracy is ±1 bucket-tip up to 0.25", after which the 4% accuracy level takes over. For example, for a total of 0.1" rainfall, the accuracy would be ±1 bucket-tip or ±10%.

This is the reason why the gauge accuracy cannot be checked for small amounts of rainfall. A period of heavy but steady rainfall totalling perhaps at least 0.5" over a period of 12-24 hours would be ideal.

Calibration by comparison with a reference gauge

The obvious way of checking the VP raingauge is by comparison to the reading of a trusted reference rain gauge. There are two caveats here. First the reference gauge must be placed almost literally next to the VP ISS and at the same height, if differences in exposure are to be avoided. Second, the reference gauge must be of known high accuracy, preferably a professional meteorological gauge with at least a 4" aperture. There is little point in using a cheap reference gauge of unknown accuracy for any but the crudest of checks. And remember that even a professional gauge will probably not be accurate overall to more than a few percent.

Calibration by simulating rainfall

An alternative calibration approach is to drip a known volume of water through the raingauge and to oberve the resulting reading. The required volume may be easily calculated as follows: The effective internal diameter of the Davis VP raingauge aperture is ~165mm, giving an area of 21382mm^2. One inch (25.4mm) of rainfall would therefore correspond to a volume of 544ml (18.39 ounces US). This volume needs to be measured out as accurately as possible, preferably using scientific volume measures, and dripped through the rain gauge over a period of 30-60 minutes, so as to stay within the maximum equivalent rainfall rate for maximum accuracy. (NB Even this calculation is not strictly accurate as the tipping buckets actually work on the weight of water and not its volume. The accuracy of the raingauge calibration will therefore vary the temperature of the water used for calibration or more strictly with its density).

Adjusting the raingauge

If, after careful and repeated checking, you feel that your raingauge is in error by a significant amount, you can calibrate the Davis Rain Collector by adjusting the height of the screw stops below each bucket inside the rain collector. Setting the screws higher will increase the rain amount and vice versa. Be careful that each set screw is set to exactly the same height.