[NLRS] RF read water meters

Sun Jul 22 12:39:37 EDT 2012

My current water meter is located in the downstairs apartment which
has been vacant for a couple years now. The meter has a pair of wires
which go to a plug on the outside of the house. It has a battery on
the meter. It seems to me they have to replace the battery about every
5 years. I have to let them in (I have a key to that apartment) in
order for them to replace the battery.

73, Zack W9SZ

On 7/22/12, Dr. Gerald N. Johnson <geraldj at weather.net> wrote:
>
>
>
>
> On 7/21/2012 6:23 PM, Doug Reed wrote:
>>
>>
>> I'm slightly surprised by the internal battery since that will require
>> them to perform a service call very 10 years. But that is built into the
>> estimated lifetime cost of the new meter.... Once every 10 years to
>> replace a battery has to be cheaper than 4 times a year to read the
>> meter.....
>
> Probably like electric meters, the meter ought to be calibrated at least
> every 10 years by some state laws and the state of the art of Automatic
> Remote Meter reading changes so much that 10 year old hardware isn't
> worth fixing anyway. The previous meter readout here didn't last 6 years
> anyway. This one may do better. The one at my farm has failed once in
> the past 18 or so years, may have filed again. Consumption there isn't
> high enough now to detect whether its working or not.
>>
>> I would bet there is a PLL based transmitter in the box and the
>> operating frequency is based on a programmed multiplier off the CPU
>> crystal. That is pretty common these days. The CPU crystals are not very
>> accurate but usually end up being a bit better than SAW-based
>> transmitters.
>
> Could be. With a transmitted bandwidth of 405 kHz, the center frequency
> doesn't have to be held to within 0.1 ppm to be found. A PLL would be
> handier and less costly than a gaggle of SAWs for the three frequency
> version and just wouldn't be practical for the frequency hopping device.
> The FCC filings show a continuous spectrum for the hopping mode, but it
> could be a software accumulated result of testing over a long time and
> that flat top could be from the DUT having used the frequencies all
> equally.
>>
>> I would expect when they say hopping they mean each transmission is on a
>> different one of those three frequencies and the data collection site
>> would simply have three receivers on one antenna. This would improve the
>> chances of a transmission being heard in a crowded metro environment or
>> apartment scenario. Although I'm surprised they don't have some sort of
>> random timing between transmissions, either based on usage or TX serial
>> number, or a combination.
>
> Hopping by FCC regulations requires more than three frequencies, the
> test reports say for their bandwidth 25 are required and used.
>
> Since the transmitters don't have receivers to trigger them, in the
> drive by situation they want them to transmit often so the odds of the
> mobile receiver being in range for at least one transmission is high. I
> fully expected the meter units to be transponders and so looked for
> radiation of requests from the monitor and found none. For this system
> the monitor and the mobile receiver are passive waiting for the bursts.
> There's sure to be QRM in an apartment complex with individual water and
> gas meters using this scheme, but the random clocks and short data
> bursts and repeated transmissions should solve most of those. On my
> water system, they gave me the monitor and I read it at bill paying
> time. I can read it at any intervals (with 4 second updates) to check
> for leaks, or the consumption of some water using event, like a shower
> or toilet flush. It has the capability of giving updates of consumption
> over a couple programmable time periods which I've not used. The rural
> water system is planning on going away from customer reading to a
> driving meter reader. I presume that's because they find some customers
> fudge the reading to save on paying bills and when the company makes an
> annual or biannual check reading there are a few wild errors. The
> electric coop I used to buy from made that change also. I know on the
> electric bill I found that based on their rates that if I fudged high
> one month and low the next that the total of the two bills was a few
> cents less than paying a leveled average.
>
> When the meter reading isn't heard, there is plenty of room for an
> estimated bill. Last summer the electric company here estimated my
> August bill as my highest for the year, but they didn't know that I was
> away 17 days that month with minimum power consumption especially no AC
> running. The next month they read the meter and that bill was the lowest
> for the year.
>
> I know from courtroom experience that utilities keep detailed
> consumption records for many years, so they have a history of power
> consumption that they can dig out to show errors in metering or cheats
> at metering but I've also found they didn't do that as much as they
> could until they thought they had a metering error either their fault or
> from customer meter tampering. I cost one company about $40K in alleged
> back bills by showing from the nursing home bills that went back further
> that the meter multiplier error was made earlier than the power company
> thought (and their local meter guy admitted) and that the metered power
> consumption had a very consistent pattern around the year until the
> meter factor was doubled when the power company finally discovered it.
> In their testimony they included data from another nursing home with the
> same number of beds at the same latitude where they moved the meter
> after swapping meters for calibration. The metering transformer was
> inside a transformer case and so could not be inspected by the operator
> or its engineer (me) to check the multiplication factor by the wire
> routing.
>
> The power company discovered the error and went back and figured up the
> correct bills for 8 or 10 years and put in a demand to the nursing home
> to pay the corrected bill which came to aome $25K, and then whan that
> wasn't paid, added monthly interest. By the time it went to trial the
> bill was about $40K. They based the lawsuit on the state law that says
> they can't give any customer a discount. The same sentence continues to
> say "can't cause a customer hardship." Where the income for the nursing
> home was largely paid by federal funds audited annually and the majority
> of the past clients were dead, there was no way for the nursing home to
> go back and recover the doubled power costs. Worse because of the low
> readings they didn't update lighting or old AC units and in their chain
> they won the annual award for low energy conservation. I told the judge
> I sure was glad I'd not been hired to improve their energy consumption
> because I'd have detected the meter multiplier error which would have
> ruined my energy savings results because all my techniques would not
> have reaped the forecast savings. I said, "I don't like being tarred and
> feathered and don't think riding a rail out of town is comfortable."
> Anyway the trial judge ruled the nursing home didn't have a defense and
> should pay up. The Iowa appeals court ruled we did have a defense and
> there should be a full fledged trial, not just one to present evidence
> for appeal. At that point the power company went silent and ate the loss.
>
> That power company wasn't exactly being reasonable demanding the
> customer pay for all the consumption and bill rates when the error was
> all the utility's. One other power company chief engineer I talked to
> said that they had made such errors and rather than the full bill they
> requested the customer pay the utility's incremental power cost, e.g.
> their cost of coal for the added KWH. But they didn't sue over it.
>>
>> Ten years ago ITI/GES built an alarm sensor with a rated 10 year battery
>> life using a 3.6V 2Amp-hour AA-size lithium battery. The only reason it
>> was rated at 10 year battery life is because the battery manufacturer
>> wouldn't warranty the batteries for 20 years. We based its battery life
>> on having under 10ua standby current. New designs 3 years ago had
>> standby current under 1ua. Chip technology had improved a lot...
>>
>> But I have to say a 4 second update rate is very high and will reduce
>> battery life considerably. I don't understand why they want that fast an
>> update rate instead of just using a longer counter in the meter. I could
>> see having data that fast if they want to graph your water usage every
>> second of the day, but that really makes little sense. But maybe they
>> have a sliding scale and slow down the TX rate if there is no change in
>> the reading?.... But if you have a fixed rate it is easier to know when
>> there is a problem....
>
> The short time interval is to allow driving by at 30 mph because the
> meter module is not a transponder, just a blatter, like APRS. The duty
> cycle is short, like 1.76 ms every 3.98 seconds, like .000442 of .0442%.
> In ten years the total transmit time is under 39 hours. FCC tests show
> 11.5 mw transmitted power. I expect the controller takes some power to
> run the 3.98 second timer, but modern PIC chips could do all these
> timings, wake up by timer, count meter turns by waking up for each one,
> and idle at microamps. Two weeks ago I bought MCHP stock and its beat
> the market and my other recent investments and pays a 3.5% dividend. So
> I'll probably be more partial to PIC chips since they are making me money.
>
> There are systems using a local fixed receiver that's networked at 220
> or 450 MHz to eliminate the mobile reader. Galaxy by Badger is one.
>>
>> If you want some major power for long term low current usage, take a
>> look at the size DD lithium batteries from SAFT. I think they were
>> 14Amp-hours in a double-D size package. They were sounding pretty good
>> for an Antarctic data collection project except they were only rated to
>> -40 degrees Centigrade rather than -60 C..... :-)
>
> 15 20 years ago they were popular for powering ham balloon transmitters
> and telemetry.
>>
>> 73, Doug Reed, N0NAS.
>>
>>
> 73, Jerry, K0CQ
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