The Nor'Easter and Vigilant
a summary by
With the loss of Trade-Wind Instruments, and in the need for anemometer to replace my defunct Trade-Wind A-2 and DGRED, I did some research and decided to get equipment made by Maximum. The company had a good reputation, and their anemometers looked fun and interesting. What follows is a summary of my experience with two Maximum instruments, useful for those who are thinking about buying such equipment, or for those who are interested in learning a bit more about anemometers they already have.
The Maximum Nor'Easter
I purchased a Maximum Nor'Easter in August 2001 and immediately set it into operation. This is the company's bare-bones anemometer-on-a-budget model. I got the entire system on sale from Grant Point Marine's online ordering, for about $80.00, and immediately set it into operation. At first I was a bit disappointed. The Nor'Easter is a digial system that samples at a rate of once every 3.4 seconds. In comparison to a number of digital systems, that sample rate is pretty decent, but to someone who's used to analog systems like the Trade-Wind A-2, and the rapidly-responding digital DGRED, the Nor'Easter seemed lacking. After watching the system in operation for awhile, it soon became obvious that during many gusts the highest velocity occurred between the anemometer's 3.4-second samples. A good steady wind would show up well on the system, but gusty winds tended to be under-represented. At the time, my wind exposure wasn't very good, with blocking trees from many directions. In these situations, average wind tends to decrease, while relative gustiness increases. Thus, even with interference, the highest instant gusts can be similar in a place with much turbulence to those places with clearer exposure and steadier winds, even with a lower average wind in the foremer. If you're looking for high wind readings, the Maximum Nor'Easter is not a good instrument for a turbulent site like the one I had. For a place with open exposure, it should do well. At my site, a quick gust would occasionally land at the right moment during the anemometer's steady 3.4-second steps, and register, but most of the time the highest portion of the gust was missed.
Just What Does a 3.4-second Sample Rate Mean?
Partially to test the idea that the Nor'Easter was missing the highest segment of many gusts, I later bought a Maximum Vigilant, which is an analog anemometer with a continuously reading display (an examination of the Vigilant appears below). As per discussion with a technician at Maximum, I set the Nor'Easter as a repeater to the Vigilant, this repeatability being one of the selling points of Maximum systems. Thus, both displays were set up to show readings from the same cups/sensor. Once this was done, I set up a digital video camera to record the anemometer's readings. Using video capture software, I was able to examine the video samples frame-by-frame, with a 1/30-second resolution. To keep the study manageable, I sampled the Vigilant and Nor'Easter at 0.5-second intervals. Careful review of long wind speed records had shown earlier that a 0.5-second time resolution captured the highest reading on the Vigilant nearly 100% of the time. A half second is about seven times the resolution of the Nor'Easter. A sample of just one gust appears in the graphic below in Figure 1.
Figure 1 clearly reveals the smoother resolution possible from the analog Vigilant, and the relatively rough resolution of the Nor'Easter. It also reveals a case where the 3.4-second sample landed on the peak of the gust, which had a duration of about 2.5 to 3.0 seconds. In this sense, this graphic does not support my claim that the Nor'Easter's 3.4-second sample rate misses the highest velocity during a gust. However, if the gust happened about 2.0 seconds earlier or later, the highest speed would have been missed.
Probably a more curious fact about Figure 1 is that the Nor'Easter seems to be reading different speeds from the Vigilant. Indeed, the Nor'Easter was reading about 2 to 3 mph low when compared to the Vigilant up until the peak of the gust, when it suddenly read 2 mph higher. Maximum claims plus-or-minus 3% accuracy for the Nor'Easter, which would mean 19 to 21 mph for a 20 mph gust. The Vigilant's accuracy is supposedly the same, and could have been reading low at this time, accounting for the 2 mph difference at the top end of the velocity reading. This does not explain the 2 to 3 mph difference at the low end (4 to 13 mph). Close examination of Figure 1 suggests that the Nor'Easter may have an approximately one-second delay between sample and display, which would account for most of the velocity disparity between the two systems.
Even despite the Nor'Easter's 2 mph advantage which is carried for about 3.5 seconds at 22 mph, the average speed over the 12.5 seconds shown in the chart is nearly 2 mph lower than the Vigilant. I'm not sure if this is because a slower sample rate might tend to have lower long-term averages, or that the two instruments have a 2 mph difference in calibration, with the Vigilant typically higher than the Nor'Easter. I'd have to take a look at longer-term datasets, over a broader range of wind speeds to determine this, something I might do when I have the time.
Another way to see how well the Nor'Easter's 3.4-second sample rate does next to the Vigilant's continuous readout is to make a scatterplot of maximum readings during specific gusts. Figure 2, below, compares the peak gust for the two different anemometers during a moderate wind event at my home on February 7, 2002. This chart shows the results of every gust of 20 mph or higher on the Vigilant for the time period 18:15:09 HRS PST to 19:45:58 HRS PST. VNT is Vigilant, NER is Nor'Easter. It is far more revealing than Figure 1.
Figure 2 reveals that, for an individual gust, a peak velocity of 20 mph indicated on the Vigilant can result in a broad range of readings on the Nor'Easter, in this case 10 to 21 mph. What this is saying is that some gusts to 20 mph happened quick enough to be missed almost entirely by the Nor'Easter. There were five gusts in the range of 20 to 21 mph on the Vigilant that resulted in maximum readings of just 10 to 11 mph on the Nor'Easter. There were 21 gusts of 20 and 21 mph on the Vigilant (out of 38 total datapoints), so the Nor'Easter was showing about 10 mph low for 24% of the gusts. Since the background--average--wind speed was probably around 10 mph during these instances, the Nor'Easter was, in essence, missing the brief 20-21 mph gusts entirely.
In Figure 2, the variance appears to decrease with higher velocities, but this is most likely due to the fact that the total number of samples reduces with higher velocities. Note that the peak gust of 27 mph on the Vigilant resulted in just 23 on the Nor'Easter--the peak gust for the storm wasn't quite captured by the 3.4-second sample rate of the digital anemometer. Note that the R-square value for this dataset is 0.14, showing a weak correlation between peak velocity on the Vigilant and Nor'Easter systems for individual gusts in the narrow range of 20 to 27 mph (for a gusty location). The disparity between highest readings has also appeared at faster speeds. On March 21, 2002, an observation of a peak instantaneous gust of 42 mph on the Vigilant resulted in a peak of just 31 mph the Nor'Easter.
Figure 3, below, shows two video frames from one of the gusts that appears in the Figure 2 dataset. The first frame shows a gust to 22 mph on the Vigilant, with the Nor'Easter trailing behind, indicating 6 mph. Just 0.4-seconds later, the Vigilant's needle has dropped to twenty as the gust slowly trails away, and the Nor'Easter has nearly caught up, indicating a velocity of 18. This particular datapoint went down as Vigilant 22 and Nor'Easter 18 in the dataset.
3.4 Seconds is Not All Bad News
The 3.4-second sample rate isn't all bad. Peak gust is just one measure of wind speed. There's also peak sustained gust. Averaging two or three samples (3.4 to 6.8 seconds of wind) probably yields results much closer to the National Weather Service standard 5-second peak wind (adopted in the 1990s with the installation of the Automated Surface Observation System), than a measure of instantaneous gust. Instantaneous gust was utilized by the NWS pre-ASOS.
Also, for someone with a degree of patience who's looking for a low-cost way of measuring average wind speeds, the Nor'Easter is likely a good buy. The even sample rate offers a quick way to calculate things like 30-second, 60-second and 120-second averages. Simply note the reading for each sample over the required number of samples for the various averages, then average the result. Ten samples approximately equates a 30-second average, 18 samples a 60-second, etc. I used the Nor'Easter to calculate 30 and 60 second averages on the fly during a number of wind events. What about the difference between the Vigilant and Nor'Easter indicated in Figure 2, above? That could be a result local to my systems during that brief 12.5-second sample period. I wouldn't worry about it too much.
Indeed, I see the Nor'Easter as a nice science education tool for children. It offers the opportunity to teach kids hands-on how to calculate/understand average wind speeds while providing practice in utilizing the mathematics of averaging, hi/lo, and mean. The minimal cost of the system means that it would be accessible to a broader range of schools than more expensive weather instruments.
If there's a feature I'd like to see added to the Nor'Easter, it's simply a little dot that blinks off and on with each sample, to distinguish individual samples when the velocity doesn't change. Of course, I wouldn't complain if a button was added that, when pressed, would show the current average velocity on the display, preferably a 2-minute reading that would be akin to that utilized by the National Weather Service.
The Nor'Easter is battery powered, requiring a 9-volt to operate. The advantage to this is that it frees the anemometer from the power grid, which can be prone to failure during significant wind storms--the very time that I like to have my anemometers operating. Various ads for the Nor'Easter claimed that a battery lasts about a month. To check this, I've kept records of the Nor'Easter's battery usage, which appear in Table 1, below. For this study, a battery is considered dead when the Nor'Easter starts showing 01 mph in place of 00 mph during periods of calm.
Table 1 shows that the average non-rechargeable 9-volt battery lasts about 26 days, which is close to a month. The rechargeable NiMh only lasted three days--it appears that rechargeable batteries are not compatible with the Nor'Easter, though this is just one sample.
To briefly digress from the Nor'Easter, I appeared to get a "bad" battery from Energizer, with a new Super Heavy Duty only lasting 18 days from April 27, 2002 to May 15, 2002. Aside from the one bad Energizer, there seems to be little difference in the duration between the two big brands, though this is still a small sample size. Interestingly, the less expensive Fred Meyer brand appears to keep up with the big two. I'm continuing to collect battery data for the Nor'Easter, and plan to continue posting results on this web page.
The Nor'Easter In Summary
For those wishing to witness the highest gust possible, the Nor'Easter is probably not a good choice, unless your location has very good wind exposure that results in nice, steady wind runs (as opposed to turbulent runs). As a system for calculating average wind speeds, it is good for someone on a low budget, though difficulty can arise in making the calculation when the same wind speed reading happens over consecutive samples. If you're worried about the cost of batteries, the system will consume about 12 a year, which suggests an annual cost of about $36.00, assuming an average price of $3.00 per battery. This cost assumes that the anemometer must operate all the time, which may not be the case.
Finally, though I was troubled with the 3.4-second sample rate in the beginning, the Nor'Easter has grown on me as I sought to understand just what the device was measuring. I now keep the display in the living room for quick and easy assessment of the current wind velocity when I'm not at my home weather lab.
The Maximum Vigilant
I purchased my Maximum Vigilant in January of 2002 from The Weather Store (MA) via online ordering. It cost about $250.00. As mentioned, the system was purchased to obtain a smooth wind readout for examination of the Nor'Easter's 3.4-second sample rate. Also, there's something inherently more interesting about watching a needle move in response to every little change of wind. Careful watching reveals a broad assortment of gust types, from those that quickly lift the needle to peak velocity with a slow trail off, to surges that gradually build, to a burst that subsequently holds nearly steady for 5 to 10 seconds, and to quick "puffs" that throw the needle up and back down in an instant. This kind of gust character is lost to many digital systems, and is why I prefer to have at least one analog anemometer operating among my computerized equipment.
One thing I really like about the Vigilant is the very large dial, with one mph increments clearly visible. I can see wind speeds down to the single mph from across a room, and, when closer, judging even 1/2 mph increments is possible, especially for the first 50 mph of the scale, which has wider spacing between the one-mph tick marks. The indicator's response is quick, leaving me feeling like it's showing the wind's myriad details in real-time.
There are a number of features about this anemometer that might be alien to someone who's used to other makes, people like me who have the tendency to compare new anemometers to the old Trade-Winds A-2s. Of interest are the peak gust register and associated hammer indicator needle, and the lack of solid readings below five mph.
The Peak Gust Register
The Maximum Vigilant and associated models such as the Maestro and Maestro 2-S have a narrow, gold needle with its tip bent down against the dial surface to catch the broader, white indicator needle. The gold needle is the peak gust register. During a high wind phase, the indicator needle will shove the gust register needle toward the wind's high point. To help facilitate this movement, the indicator needle has been designed to slightly waver up-and-down like a little hammer to bang away at the gust register needle. This wavering was a little disconcerting at first, as I was used to the smooth motion of the Trade-Winds indicator. However, the bouncy pointer on the Vigilant doesn't take long to get used to, though one is left wondering at times just what part of the little swing is the actual wind velocity--the down part, the up, or the middle. Of course, the variance is under one mph on the large scale offered by the Vigilant.
Despite the hammer action, the gust register has several limitations.
The gust register isn't supposed to be set below 15 mph, to allow the indicator needle some room to move at the low-energy end. Thus, for those interested in taking daily peak gust records, this isn't the instrument for the task. I encountered no mention of this 15-mph limitation from the available literature, and was a bit disappointed once I received the Vigilant and read the instruction book. Since I'm more interested in high wind speeds, this displeasure wasn't major. More an irritation.
Of greater significance, the gust register adds to the overall inertia of the indicator needle. In other words, it adds resistance to the motion of the indicator, slowing its response to short-duration gusts. I haven't bothered to measure the extent of the slowing in any controlled fashion like I did the examination of the 3.4-second sample rate of the Nor'Easter. To do so, I think I'd have to get another Vigilant, set it up as a repeater to the other and videotape the response of one dial with the gust register out of the way, and the other with the register in use. Having the Nor'Easter set up as a repeater from my Vigilant has offered the opportunity to roughly observe the limitations of the gust register. During some sustained 20 to 30 mph gusts where the indicator needle was having to shove the gust register, the Nor'Easter sometimes showed speeds two to four mph faster. My guess is that the disparity could be quite a bit greater at times. The most I've ever seen a single gust push the register is about 3 mph before the wind speed fell below the register's position. Looking at the Maximum literature, I see a notation of the register's response rate at "75% Vv / 5 seconds". If I'm interpreting this correctly, it seems to imply a reading about 75% of the actual velocity over a period of five seconds. Which means that the gust register is more a measure of sustained gust than instant gust. As mentioned in the Nor'Easter section, the National Weather Service records a 5-second peak gust these days, so the gust register reading is probably more comparable to the NWS readings than a free-swinging indicator needle showing instant bursts. Nevertheless, I like seeing the full range of each gust. During significant wind events, I use the gust register reset knob to move the gold needle out of the way and let the indicator have free reign of the dial. I've witnessed brief gusts up to 45 mph that almost surely would have made the gust register barely move had it been in the way.
No Sub 5-mph Winds
For those interested in low wind speeds--and I know a few out there--the Vigilant isn't the anemometer for the job. There are no tick marks between 0 and 5 mph on the dial, and I take this to mean that the device isn't calibrated for these wind speeds. I think part of the problem stems from the mechanism that creates the indicator needle's hammering motion. At low speeds, the needle appears to have a wider swing than at high speeds. The indicator is especially bouncy below 5 mph, and can swing over a significant portion of the space between the 0 and 5 mph marks. From the National Weather Service standpoint, I think this kind of situation was in play pre-ASOS, as readings below 3 mph/knots were sometimes indicated as estimated on the surface observation forms. Probably another reason for the Vigilant's setup is that calibration for the lowest wind speeds is difficult. Part of the reason for this is that the anemometer's cups may not be sensitive enough to actually respond to velocities of 1 or 2 mph. I think the Maximum sensors are in this category. I've run the Maximum sensor against a Davis VantagePro, in this case having the cups side-by-side in close proximity. The Davis sensor is clearly more sensitive than the Maximum. When the Davis is showing 1 mph, and even 2 mph, the Maximum cups aren't even moving. Though somewhere between 2 and 3 mph there's a response in the Maximum, and the needle on the Vigilant begins to jiggle. At 5 mph and above, both systems are in close agreement; though, like with the Nor'Easter, the Vigilant has the edge on peak instant gust, as the Davis has a 2.5-second sample rate. Incidentally, the Davis and Nor'Easter read nearly the same most of the time, the mark of carefully calibrated instruments, I'd say.
This isn't to say that the Maximum cups aren't well made. They have a very smooth action with good response times. They appear more sensitive than the Trade-Wind sensors that I used in the past. Indeed, I think one to five mph readings on the Trade-Winds are quite questionable, with the catch-up point occurring between six and ten mph.
The Vigilant in Summary
Despite some limitations, I enjoy the Maximum Vigilant, especially during blustery days that give the indicator needle a good workout. It's also quite a showpiece. For those wishing to keep daily peak gust records, the Vigilant's gust register isn't quite up to the job, and the 15-mph-plus readings that it does record are most likely peak sustained gust as opposed to peak instant gust. The Vigilant also doesn't reliably indicate wind speeds below 5 mph.
Maximum Anemometers: Some Final Notes
Maximum offers a five-year warranty on all their equipment. I think this is indicative of very reliable high-quality instruments. My Nor'Easter and Vigilant have worked flawlessly since I put them into service, despite long heat waves, cold snaps, many-day-long Columbia Gorge wind events with east gusts of 20 to 35 mph, and so on. Other respected weather instrument companies, like Davis, do not offer a warranty of the duration of Maximum's, typically having coverage for only one year. Though a long warranty isn't everything, it's something to keep in mind when looking for a new anemometer or other meteorological device.
Last Modified: September 20, 2003
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