| dpb <none@non.net>: Jul 21 07:02PM -0500 On 07/21/2017 6:13 PM, Mad Roger wrote: ... > + How accurate& precise is a reading of 300 miles on a typical tripmeter? For a specific vehicle, it really doesn't matter to determine _changes_ in mpg for a given test condition (unless, of course, you're futzing with the tire size in which case that would have to be compensated for but is doable to pretty precise number by knowing the tire profiles or simply doing the "measured mile" computation. > + How accurate& precise is a reading of 20.25 gallons on a gas pump? NIST tolerance is 6 in^3 in a 5 gal measure. AFAIK that's what all state W&M departments use for their tolerance. A NIST document of 20,000 tested meters showed 0-mean normally distributed discrepancies at about 90% bounds on the +/-6 number. The 6/5gal --> ~0.5% > + How accurate& precise is the matching of the prior fuel level done? That's entirely dependent upon the tester -- in older vehicles without the emissions control folderol on the gas tank filler spout it was pretty easy to be quite precise if one were trying. Now it would take some doing, but I suspect if really cared, one could manage to get pretty close to the same height. > No calculation can do better than the worst measurement, and worse, errors > compound when you multiply or divide. ... But properly designed 'spearmints can cause cancellation of many sources often and besides the simple "combination of error" the math of the numbers also enters into the relative magnitude of the error on the final result. In this case, for example, the second can be effectively eliminated or reduced significantly by simply taking multiple runs...then the actual level on each intermediary measurement is immaterial because whether it was high or low on any given case, the total amount of fuel is the denominator and so the fractional error in it is much smaller owing to the same presumed error in the last measurement. -- -- |
| Vic Smith <thismailautodeleted@comcast.net>: Jul 21 06:22PM -0500 >If the change itself causes, say, a 1 mpg difference, but if our >measurement accuracy is, say, plus or minus 1 mpg, then we'll never see a >measurable difference between the two test runs. Under just moderately controlled conditions, 1 MPG is actually a significant amount, and would be easily detectable using your mom and pop method, assuming the mom and pop competently applied the method. >+ Tripmeter accuracy is what in the average car over a 300-mile tank? >+ Owners ability to "match" the previous level of fuel is what? >+ Gas station pump reading accuracy is what? I never used the tripmeter for MPG, because I never bothered testing them with mile markers. Matching gas level is trivial - and it only has to done at the beginning and end of the trip. Gas station pumps - I assume they are accurate, and can't control that anyway. I'm confident that my measurements are accurate to within .1 MPG. Because I don't care about .135867 on the total. I round it down to .1 That's pretty "exact." Repeatability is meaningless when measuring MPG, unless you're driving on a covered track, with a temperature controlled environment. On every trip the MPG can vary. BTW, I don't disagree that perfect measurement of MPG in unattainable. Perfection is impossible even under lab conditions. But you too easily discount "mom and pop" MPG calculations. |
| Mad Roger <rogermadd@yahoo.com>: Jul 21 11:30PM On Fri, 21 Jul 2017 18:05:52 -0500, dpb wrote: > We'd already thrown the mileage calibration bias out as being simply > that. It can be compensated for by comparison over set measured course > and recording the offset. I agree with you that the tripmeter calculation is inaccurate to some degree, for which there are ways of "calibrating" the equipment. > Red herring for the discussion. The answer to the question depends on only 3 factors, I think. Given these three factors are critical to answer the question, I think everyone is talking out of their ass (including me) if they can't answer these three questions to validate their own thought process: + How accurate & precise is a reading of 300 miles on a your tripmeter? + How accurate & precise is a reading of 20.25 gallons on the gas pump? + How accurate & precise is the matching of the prior fuel level? I posit both the tripmeter and the previous-fill-level measurements suck. How much to they suck? I don't know. I would not be surprised if they suck so badly that the end result is a calculation which is plus or minus 1 mile per gallon in either accuracy or repeatability. > inconsistent fillup, but one can assume the pump is accurate since > they're checked by the State weights and measures folks on a regular > basis. While it will be useful to know what the accuracy and precision (repeatability) of the pump is, I think we can all assume that the pump is within something like (at least) plus or minus a few percent of what it reads. But that number can be accurate to a billionth of a gallon, and it still would be meaningless if the fill level was off by plus or minus a gallon because the accuracy of any one measurement is only as good as the worst measurement and the accuracy of the final calculation (when multiplication adn division are involved) compounds inaccuracies. Anyway, all the words are moot if we don't know the answer to 3 questions: + How accurate & precise is a reading of 300 miles on a your tripmeter? + How accurate & precise is a reading of 20.25 gallons on the gas pump? + How accurate & precise is the matching of the prior fuel level? > all in the end--it's the total. Only that random error on the final > fillup when you make the calculation at the end does that error enter in > -- and it becomes quite small by then in comparison to the total. Am I correct to understand that you are saying if you go only 300 miles on one tank, then the fill-level inaccuracy is (say) plus or minus 1 gallon per tank; but if you go 3,000 miles (obviously on multiple tanks), that the fill-level inaccuracy is one tenth of that plus or minus one gallon per tank? > And, if one computes the mean of the billion trials, the error in the > mean is quite small even if the random error in each trial is sizable. As long as the error is random (i.e., in both directions of the true answer). |
| dpb <none@non.net>: Jul 21 08:30PM -0500 On 07/21/2017 7:02 PM, dpb wrote: ... > tested meters showed 0-mean normally distributed discrepancies at about > 90% bounds on the +/-6 number. The 6/5gal --> ~0.5% >> + How accurate& precise is the matching of the prior fuel level done? ... And remember that is the "shut 'er down" tolerance, not the average...as noted, the most probable based on the NIST sample was in the +/-0 bin (<1). I didn't quite recognize what the figure was yet when first looked at it and had closed the link when I realized the significance so don't have the actual numbers at hand...but the +/-6 number was quite a way out on the tails of the distribution altho I don't know just precisely the tails percentages. And, actually while the report used "normal" in discussing the distribution, it really wasn't normal as in bell-shaped, it was symmetric and zero-mean, but the tail in each direction dropped off more as hyperbolic than a normal--hence the tail percentages would actually by somewhat lower than a real normal of same mean, standard deviation. -- |
| dpb <none@non.net>: Jul 21 08:33PM -0500 On 07/21/2017 6:30 PM, Mad Roger wrote: ... > As long as the error is random (i.e., in both directions of the true > answer). What do you not understand about "random"? And the mean is still the mean, whether it is zero or not. -- |
| clare@snyder.on.ca: Jul 21 09:41PM -0400 >quite good comparisons on recent ones with the computer-computed >results. These would be over total distances of 1500 to 2000 miles, not >just 20 miles test runs. With my scanguage on my Ranger the calculated MPG and the MPG figured out by me using a calculator and fuel volume vs mileage is generally pretty darn close. If the ScanGuage says they injectors have passed 13.7 gallons, my fillup is generally somewhere within .1 to .2 gallons. The speedo and GPS are within less than 1 kph on speed at 100kph (62Mph), and the odo within about the same. This is after making corrections over many tanks for the fuel volume adjustments. Neither of my ancient machines has a built in "trip computer" |
| clare@snyder.on.ca: Jul 21 09:47PM -0400 >I measure my gas mileage on every fillup. I get 19 to 20 MPG every fill >unless I do a lot of around town driving. Very consistent. I watch it to >see if it drops off which would mean something is wrong. Occaisionally on a longish trip I'll see how well I can drive for economy - to see if I can better the last time I did that trip. This is generally over pretty close to a full tank - and small differences in driving technique can make a HUGE difference. So can a small change in route.Or a difference in the wind. I've registered a good 25% difference in mileage between 2 trips, both trying to squeeze the last foot out of a liter of fuel. Round trip averages out the difference in altitude. |
| dpb <none@non.net>: Jul 21 08:55PM -0500 On 07/21/2017 8:41 PM, clare@snyder.on.ca wrote: ... > 100kph (62Mph), and the odo within about the same. This is after > making corrections over many tanks for the fuel volume adjustments. > Neither of my ancient machines has a built in "trip computer" I find all that perfectly believable...the speedo on the Buick I noticed on the last trip to NM was deadnuts on the wife's GPS. I presume if that's the case the odo would be, too, altho I never actually checked on it specifically. Instrumentation is pretty good and pretty cheap to get pretty good for ordinary measurements any more...electronics is a wunnerful help in many ways. :) As I've turned into old fogey, I've come to rely on the 'puter for such info more than would've cared at 20. There's just only so many times one really wants to get down on the ground and measure tire pressure after 70... :( There's getting to be a lot of fluff besides the useful, but the basic stuff is helpful. -- |
| clare@snyder.on.ca: Jul 21 10:01PM -0400 On Fri, 21 Jul 2017 13:31:01 -0500, Vic Smith >calculations by filling to the filler tube. That too is an EXACT calculation, but is still >only approximate MPG because maybe the terrain and weather may vary. >So before you ask about "accurate MPG" you have to define what that is. We'll never get that - he admits he's an "engineer" 1) Someone who gets excited obout things most other people don't care about 2) Someone who solves a problem you didn't know you had, in a way you don't understand. 3) The optimist sees the glass as half full. The pessimist sees the glass as half empty. The engineer sees the glass as twice as big as it needs to be Q: What is the definition of an engineer? A: Someone who solves a problem you didn't know you had in a way you don't understand. Q: When does a person decide to become an engineer? A: When he realizes he doesn't have the charisma to be an undertaker. Q: How can you tell an extroverted engineer? A: When he talks to you, he looks at your shoes instead of his own. Q: Why did the engineers cross the road? A: Because they looked in the file and that's what they did last year. Q: How do you drive an engineer completely insane? A: Tie him to a chair, stand in front of him, and fold up a road map the wrong way. Real Engineers consider themselves well dressed if their socks match Real Engineers buy their spouses a set of matched screw- drivers for their birthday. Real Engineers wear moustaches or beards for "efficiency". Not because they're lazy. Real engineers have a non-technical vocabulary of 800 words. Real Engineers think a "biting wit" is their fox terrier. Real Engineers know the second law of thermodynamics - but not their own shirt size. Real Engineers say "It's 70 degrees Fahrenheit, 25 degrees Celcius, and 298 degrees Kelvin" and all you say is "Isn't it a nice day" Real Engineers don't find the above at all funny. |
| clare@snyder.on.ca: Jul 21 11:01PM -0400 On Fri, 21 Jul 2017 19:05:32 -0000 (UTC), Mad Roger >balancing out the overestimations, but I'm not going to quibble that more >calculations done over time are likely going to randomize the precision and >accuracy fluctuations over time. Actually it is - because you only make ONE calculation. The measurement accuracies do not change. The precision gets better, because you are not using numerous mileage measurements that can only be accurate to the closest 10th of a mile or KM (more accurate in the metric system becuase a KM is smaller than a mile) The precision is now 1/10km over 5000 km instead of 1/10 kn over 500, ten times. Your accuracy on the fuel used is to the 10th of a liter (or gallon if you are a Yank)- again more accurate with the metric system because liters are smaller than gallons. So your accuracy is to the closest 10th of a liter 5 times - and the accuracy of the fillup is only the closest you can get it ONCE instead of 5 times. Accuracy of fuel used will be, at the very most, 5X 1/10th liter more - that's plus half a liter over to -0 liter under over 365 liters at 20 miles per US Gallon that's within better than 1.5% (1.369) at the outside.(assuming the calibration of the pumps is accurate - pumps are calibration tested on a more or less regular basis - when I was "in the business" we were still running imperial gallons for the most part - the pumps were inspected and certified accurate to within 1/10 gallon in 5 gallons ( the closest the meter could read) IIRC when the switch to metric was made, it was 1/10 of a liter in 20 liters (the size of the test container remained virtually the same) so accuracy improved by roughly a factor of 4. If I kept track of the fuel mileage on my vehicle over a period of 50,000 km, the accumulated average fuel economy could be easily calculated to within that percentage of error. ( I used to do that when I ran a vehicle log for business purposes) >in the same direction in either precision or accuracy, in which case it's >*not* going to balance out over time. It will be consistently wrong, over >time. Or consistently right. If you KNOW the accuracy of the speedo, it is a simple mathematical correction to achieve accuracy. The speedo may vary in accuracy because it is an inductive coupling device on a mechanical speedo, while the ODO will not vary as it is a direct geared connection to the driven wheels. With electronic speedos and odos, their calibration does NOT change. The only vatiance is tire wear ( aproxematelt 3/8 inch difference in diameter of a , say, 24 inch diameter tire, over it's lifetime - and that wear is pretty linear - so it is not rocket science to work in a correction for that too if you want to be a very anal engineer. >purposes, the randomization of measurement results will be half the time >underestimating and the other half the time overestimating - such that they >could balance out. Or they could not - better to eliminate the randomization, or account for it in calculating accuracy. >> quite good comparisons on recent ones with the computer-computed >> results. These would be over total distances of 1500 to 2000 miles, not >> just 20 miles test runs. I've averaged it over 240,000 miles - - - >mom-and-pop test of dividing the number of miles driven based on the >tripmeter reading by the pump indication of gallons used to fill back up to >a presumed similar previous starting point of amount of fuel consumed. I'm sure I could claim accuracy to closer than 1 MPG, but what good would it do over 240,000 miles??????? (and how could you prove me wrong?) For COMPARISON testing, accuracy is not important - only precision and repeatability. On my electric conversion I could compare one type of tire to another by driving a given distance and route on one set, measure the watt hours of charge used, and compare to a different set of tires over the same route under the same conditions and KNOW how much better "mileage" I would get with one tire over the other. Modifying the tune on my '63 Valiant, or a customer's Celica, or whatever - I could do a "before and after" run of 5 miles with my calibration can and know, to the ounce, how much more or less fuel was consumed over the same route, Using the "official" fuel mile tester I could measure to the cc over a half liter - that's an accuravy of 1 part in 500, or 0.2 percent. If I had a "rolling road" I could repeat the drive cycle accurately too - but I only had access to that at trade school (a chassis dynamometer) Not as easy to do today with fuel injected cars - but dynos are a LOT more common today than they were 40 to 45 years ago . . . and more programmable. If you know the cd of a vehicle today, a computer simulation can run a vehicle over a virtual course, correcting for ambient wind, changes in elevation, accelleration (knowing mass of the car) -every conceivable condition - to make direct case to case comparisons EXREMELY accurate. (and fuel measurement technology has advanced so it's very simple to very accurately neasure the amount of fuel consumed as well - and also get very accurate measurements of instantaneous consumption - and with strain guages even know EXACTLY how much horsepower is being delivered to the road to figure out specific fuel consumption - All stuff you "engineers" should understand. >Remember, the resulting accuracy can't possibly be better than the least >accurate measurement. Which can vary from no better than a SWAG to pretty darn close, even for the "mom and pop" or "hobyist" to EXTREMELY accurate for the engineer. |
| clare@snyder.on.ca: Jul 21 11:57PM -0400 On Fri, 21 Jul 2017 21:51:42 -0000 (UTC), Mad Roger >have an "exact" number, and, I posit, that you can't even get remotely >close to exact, using the standard mom-and-pop tripmeter/pumpmeter method. >+ Tripmeter accuracy is what in the average car over a 300-mile tank? Whatever it is off, repeatability will be very close to 100%. 300 miles, repeatabilty to within less than 1/10 mile, or .2% >+ Owners ability to "match" the previous level of fuel is what? If he's as smart as the average fifth grader, within less than a cup at the same station, in the same spot, Lets nake it within a pint - that is 1/8 gallon in 15 - call it .8% on 15 gallons - - - so at LEAST within 1% >+ Gas station pump reading accuracy is what? Again, repeatability within well under 1/10 gallon per fill (15 gallons) - about .6%?? Accuracy doesn't mean anything if the refill is at the same pump as the initial fill. Again, if you are in the "metric world" instead of the USA, accuracy improves by a factor of almost 4 on the fuel measurements, and 1.6 on the distance. All of this accuracy can be accomplishes with NO special equipment. Where the REAL fun comes in is duplicating the "drive cycle" - for the average driver, on the average road, "virtually impossible". If you have a closed course, and you are a VERY good and consistent driver, - perhaps you can get within a REASONABLE approxemation (repeatability over 5 runs, perhaps within less than 5%) - in open traffic, you'l be doing VERY good to get repeatability better than within 10% on a short run - over 300 miles, averaged over 5 runs (total 1500 miles) mabee within 1% on open road, or 5% running with traffic. Repeatability gets a LOT better over a short distance where fewer variables are involved. (Start from the gas station, accellerate to 30MPH in 2 blocks, enter the "expressway" and accellerate to 60mph by the first exit, maintain 60MPH to the 5th exit, slow down and exit the highway, stop. pull away from stop and re-enter the highway going the opposite direction, accellerate to 60 mph as you merge with traffic, decellerate from the 4th exit to the third exit, return to the gas station Repeat. Repeat Repeat. That kind of driving can be very repeatable. Fill with gas, Drive 3 blocks to the highway, drive 100 miles to "the city" Drive 5 miles across the city to restaurant, sports arena, or place of work, then return Repeat Not much chance the 2 trips will be anywhere close. (I have had variances of more than 25% between 2 trips between Waterloo and Barrie Ontario over the same route, at the same time of day, and day of the week (and even the same month) - (even when the overall travel time was very close to the same for the round trip). generally WITHIN 10% IS PRETTY DOABLE - AND AT 20mpg THAT'S +/- 1 mpg at best If you are in open country with very little traffic, repeatability gets MUCH better. Driving back and forth from Flagstaff to Jeddito Arizona you could likely repeat within well less than 1/4 MPG in the middle of the week - or from Enid to Chickasha Oklahoma - or from Saskatoon to Regina.(very little traffic variability) |
| clare@snyder.on.ca: Jul 22 12:07AM -0400 On Fri, 21 Jul 2017 22:05:13 -0000 (UTC), Mad Roger >is about plus or minus 1%. >Notice the accuracy is *always* high while the precision is random around a >set point. True of the speedometer, but NOT of the odometer. The odometer repeatabilty is as close to 100% as you will get even with a cable driven odometer. (it is a directly geared measuring device with ZERO vatiability - X number of cable turns per mile from the day it's made till the day it is scrapped ( generally 1000 turns per mile, but some older cars were 600 turns per mile, some motorcylses 1450, etc - but they never change) With electronic speedos and odos (virtually all cars today less than 15 years old) repeatability is almost 100%. Accuracy CAN be very close to 100% too, as on most cars under 10 years old today, the speedometer can be accurately reprogrammed to the tire diameter so repeatability is only affected by tire wear (mabee 3/8 inch in 24 over the life of the tire) |
| clare@snyder.on.ca: Jul 22 12:11AM -0400 On Fri, 21 Jul 2017 22:25:04 +0000 (UTC), root <NoEMail@home.org> wrote: >As a somewhat off-topic point, manifold vacuum is directly related >to instantaneous mpg. It is relatively easy to install a vacuum >gauge in the driver's compartment. Directly related? but not necessarily 100% linearly related High manifold pressure (low vacuum) means heavy load which means poor mileage. The reverse is also true - but calibrating vacuum to MPG is virtually impossible with any level of accuracy. It WILL give you a good, better, worse indication though. Keep the vacuum up and you will get better mileage. |
| clare@snyder.on.ca: Jul 22 12:18AM -0400 On Fri, 21 Jul 2017 23:13:15 -0000 (UTC), Mad Roger >+ How accurate & precise is a reading of 300 miles on a typical tripmeter? >+ How accurate & precise is a reading of 20.25 gallons on a gas pump? >+ How accurate & precise is the matching of the prior fuel level? How many ingels can sit on the tip if a pin??? That's about how ridiculous this whole discussion is getting |
| rickman <gnuarm@gmail.com>: Jul 22 12:26AM -0400 > difference in mileage between 2 trips, both trying to squeeze the last > foot out of a liter of fuel. Round trip averages out the difference in > altitude. Nearly all my driving is on secondary highways so I pretty much am driving at pretty optimal speeds for mileage although there are some traffic lights, they tend to be miles between stops. I have developed fuel efficient habits so I nearly always squeeze every last MPG on my trips. I have a manual, so I slip it out of gear and coast to lights and nearly always accelerate gently. I leave a lot of room to the car in front so I can ease up on the gas rather than hit the brakes. I think I am doing about as well as can be expected all the time, so my mileage seldom varies unless I do more city driving. High 19 or low 20 MPG, very consistent. -- Rick C |
| rickman <gnuarm@gmail.com>: Jul 22 12:46AM -0400 Mad Roger wrote on 7/21/2017 7:13 PM: > what they are, which means nobody knows what they're talking about. > Assuming the tripmeter/pumpmeter calcultion is the method used, > + A tripmeter of 300 miles is neither accurate nor precise I don't know what you mean. I have checked my odometer against the markers on the highway as well as against my GPS (I think the highway markers are more accurate than the GPS). It is spot on with the current tires to 1% or better. I had some larger tires at one point and it made the odometer read a bit low, also the speedometer. BTW, someone said something about one being accurate meant the other was accurate and that is not necessarily true. My speedometer is mechanical and so has a separate calibration factor. With the present tires it reads a bit high, about 1 to 1.5 MPH at highway speeds. That one is harder to calibrate than the odometer (which is pretty much on point) because it is hard to maintain a constant speed for long enough to get an accurate reading even with the cruise control. But with lots of readings I am pretty confident these numbers are right. So my odometer is accurate and precise. > + A pumpmeter of 20.25 gallons is likely relatively accurate & precise Of course it is. States inspect them at some point. > + Matching fuel level in the tank isn't even close to accurate nor precise I don't agree. I let the pump click off and then continue to pump for a number of more clicks until it cuts off immediately. I always need to run at least another fifteen miles before I am home so that is better part of a gallon burned so I don't need to worry about the gas warming up and running out of the tank. I believe this makes for very consistent fill ups. My MPG results pretty well show the consistency of my measures. > I think most of us would probably assume the pumpmeter is the most accurate > and the most precise, but the other two measurements aren't even close to > accurate or precise. You know what happens when you assume... ;) > I posit that the best you can do, overall, after running the calculation, > is something like plus or minus about 1 mile per gallon such that 20 mpg is > actually anywhere from 19 to 21 miles per gallon actual. I think one time in nearly 20 years I got 22 MPG. I think I can count on my fingers the times I got 21 MPG. These days with nearly all my driving on the highway it is much less than 1 in 20 fills that I see less than 19 or even 19.5 MPG. It is nearly always just under or just over 20 MPG, more just under :-( If I were the dancing type I would have a little happy dance when it actually is over 20 MPG, lol. It makes my day. > + How accurate & precise is a reading of 300 miles on a typical tripmeter? > + How accurate & precise is a reading of 20.25 gallons on a gas pump? > + How accurate & precise is the matching of the prior fuel level done? I think the consistency of my MPG readings show how well each of these can be measured. As you say, the pump is going to be dead on. Other than scale error which can be calibrated out the odometer will be very good. Filling your tank can be good as well. It's not like they design gas tanks to have air pockets. > + How accurate & precise is a reading of 300 miles on a typical tripmeter? > + How accurate & precise is a reading of 20.25 gallons on a gas pump? > + How accurate & precise is the matching of the prior fuel level? You don't need to know any of this specifically. You just need to measure your fuel mileage and measure the accuracy and precision of the results. Why do you care which of the three has what specific degrees of accuracy and precision? You care about the accuracy and precision in the result and you can measure that. Remember there are other factors as well that actually impact your MPG from tank to tank. They will show up when trying to measure any one influence so might as well calibrate them in too. -- Rick C |
| rbowman <bowman@montana.com>: Jul 21 11:25PM -0600 On 07/21/2017 07:55 PM, dpb wrote: > Instrumentation is pretty good and pretty cheap to get pretty good for > ordinary measurements any more...electronics is a wunnerful help in many > ways. When you consider how the old speedometers worked it's amazing they came anywhere close to reality. I had a '60 Plymouth where the speedometer looked like a red bar progressing across a horizontal display rather than the usual needle. The guts were a tube about a foot long and an inch and a half in diameter suspended in bearings and loaded with a spiral spring. The mechanical cable from the tailshaft of the transmission tweaked the tube with each revolution via a magnetic link. It was an analog integrator with the spring controlling the tube's rotation. The standard dial type was the same principal but the Chrysler engineers went out of their way to be weird. That was also the era of the pushbutton Torqueflite tranny and left handed lugnuts on one side. A lot of modern speedometers are just as bizarre converting a perfectly good digital pulse train to an analog voltage to drive a dial rather than going straight digital. But now |
| rbowman <bowman@montana.com>: Jul 21 11:29PM -0600 > Occaisionally on a longish trip I'll see how well I can drive for > economy - to see if I can better the last time I did that trip. I'm a fairly economical driver but on longish trips I'm more concerned with getting there. 80 mph guarantees the fuel economy is going into the dumpster. |
| "pfjw@aol.com" <pfjw@aol.com>: Jul 22 05:09AM -0700 Once again: This horse is dead, skinned, flensed, tanned, jerked and dried. And whatever life it has clung to for these many repetitive, redundant and often ridiculous posts is based on the essential confusion between and conflation of "Accuracy" and "Precision". These do not mean the same thing, never have the same application, and seldom are on even parallel tracks when used properly. When dealing with furlongs per bale, sufficient accuracy may be had using no more than 20% of the fingers of one normal human hand and the track markers. Miles per gallon, and kilometers per liter are quite similar, requiring only second-grade arithmetic to solve within repeatable limits. Full stop. Peter Wieck Melrose Park, PA |
| rickman <gnuarm@gmail.com>: Jul 22 09:22AM -0400 rbowman wrote on 7/22/2017 1:29 AM: >> economy - to see if I can better the last time I did that trip. > I'm a fairly economical driver but on longish trips I'm more concerned with > getting there. 80 mph guarantees the fuel economy is going into the dumpster. I forgot, I can tell the difference in fuel economy by driving 65 MPH rather than 60. Driving at 65 very much (only about 1/3 of my trip allows that) will assure that I only get 19 mpg rather than pushing 20. There is a 10 mile stretch with only one traffic light and a posted speed limit of 45 MPH. If I can get up to 50 so I'm solid in fifth gear my mileage rocks. -- Rick C |
| "Colonel Edmund J. Burke" <burkesgurlz@std-girls.com>: Jul 22 06:27AM -0700 On 7/20/2017 5:08 AM, Mad Roger wrote: > What is a realistic accuracy & precision of typical MPG measurements when > measured by the consumer using the typical method of dividing their > tripmeter miles by the gas-pump gallons during fillup? Stuff like that doesn't concern a man of my means, but in a pinch I could measure my mileage knowing the actual distance to my nearest Denny's, America's Favorite Diner. This is the "meat and potatoes" of the argument. All else is just fluff. |
| amdx <nojunk@knology.net>: Jul 21 09:47PM -0500 I have a CZH-05B FM transmitter. It recently went low power. It will transmit but not more than 20ft. I looked in and found an over heated resistor, maybe two, they are close together, a shorted transistor and a 9 volt regulator putting out 10.8V. I made an assumption that the output transistor was OK since it did transmit, and these parts were in the predrive circuitry. I ordered the parts, installed them and not much change in the signal, I think there is a little more output but it's still not right. So I opened and checked the 9v regulator output. Hmm, it 11.x volts output. The part I removed is labeled 78L09, it is an sot89 part. The part I order is the same. The part I got is labeled 8H612. I'm not sure it is the right part. I have searched for an 8H612 and find nothing. The part I ordered is supposed to be a ST Micro part. I don't know how they mark their parts, But I expect it would say 78L09. I will try to call tomorrow and verify. uh, Monday. The second problem, I should have checked the output transistor, it is shorted. The part on the transistor is K2 092, Marked K2 and then under that is the 092. I have a second unit that has the output transistor marked K2 021. These are surface mount transistors, I can not find any information on these transistors. Help with either problem appreciated. Mikek |
| dansabrservices@yahoo.com: Jul 21 08:41PM -0700 Look up the SMD code of K2. This will translate into a more reasonable number for ordering. Dan |
| Phil Allison <pallison49@gmail.com>: Jul 21 09:06PM -0700 amdx wrote: -------------------- > I have a CZH-05B FM transmitter. ** I cannot find a schem for this thing. Can you post one ? .... Phil |
| amdx <nojunk@knology.net>: Jul 22 07:54AM -0500 On 7/21/2017 11:06 PM, Phil Allison wrote: > ** I cannot find a schem for this thing. > Can you post one ? > .... Phil I can't find a schematic for my model. The closest I have found is this. > http://www.czhfmtransmitter.com/wp-content/uploads/2014/03/Fmuser-CZH-CZE-05BcirciutDiagram.pdf I suspect this is a later model and the only similarity is the output section. My unit has a couple of pre drive transistors, where the schematic I posted the output is driven directly from an IC. I'll see if I can make enough sense of it to draw at least the output section. Mikek |
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