I'm laughing as I see the specifications in this book for a depth finder or commonly called a fish finder. But I'm seriously doing a WTF ? with how they come up with these specs. This device is of course an ultrasonic transmitter that works at 200 KHz. I see in the manual it clearly states the output power is 250 Watts RMS and also it states that it is 2000 Watts peak to peak!!! So I keep thinking with a 12 volt DC input this device must really be drawing some serious current and I'm concerned about how much battery life will be reduced using it without anything to recharge it readily on a boat. Then I finally come across the specs on the fuse. One Amp fuse !
So we have a potential maximum input of 12 watts ( or maybe 13.5 or so if the battery is really charged which if it was consuming that much would blow the fuse) and 250 Watts output RMS ??? or 2000 Watts peak to peak ? And yes it states Watts - not milliwatts. Who does Hummingbird think they are fooling? Are fishermen really that dumb? Or is this just another fish story in which Hummingbird (the depth finder manufacturer) has taken exaggeration to new levels? Or is there someting magical about this unit? Or am I just missing something obvious? Questions questions Hummingbird. My bet is Hummingbird is trying to wow some fisherman with claimed huge power levels that are probably a thousand times higher than actual power output.
Sumpin's fishy here ;)
Just to make sure Hummingbird wasn't just having a bad day when they wrote the manual for that unit I downloaded another manual for one of their current units. It claims 1000 Watts RMS output or 8000 Watts peak to peak output. That is with 12 volts input and a 2.5 or 3 Amp fuse so a maximum of about 36 watts input will get you at least 1000 Watts output ???
it is similar to the way cheap audio amps are rated.
it isn't OU, just shady advertisement.
Continuing a little research I find other manufacturers are claiming the same. Garmin has one that states it uses a maximum 3.5 watts (power usage or input) and is so stated right in the owner manual but it puts out 100 watts RMS or 800 watts peak to peak. So this is common practice I guess for fish finders. What is going on here ?
Quote from: WilbyInebriated on July 18, 2011, 12:59:05 AM
it is similar to the way cheap audio amps are rated.
it isn't OU, just shady advertisement.
Yeah that thing with cheap audio amps crossed my mind but these aren't no-name manufacturers. Garmin is huge, is a big item on the stock market and has a top reputation. I have a hard time imagining why they would want to risk being caught in such a huge lie about their equipment specs for just one line of things they sell. I think the bigger part of their business is in GPS units by far. I still wonder if their isn't some other explanation for this huge discrepancy in power in/power out specs. I don't think it's OU but I'd like to understand what it is.
Quote from: e2matrix on July 18, 2011, 01:04:29 AM
Continuing a little research I find other manufacturers are claiming the same. Garmin has one that states it uses a maximum 3.5 watts (power usage or input) and is so stated right in the owner manual but it puts out 100 watts RMS or 800 watts peak to peak. So this is common practice I guess for fish finders. What is going on here ?
hi e2
the better audio amp mfrs usually give just the true RMS (continuous) o/p performance, and this will be conservatively inside the supply V x I(fuse) rating
the guitar and instrument amp market are usually the 'bad boys' for using a rating system like peak-to-peak to inflate the apparent performance of their devices - and so these values could appear to be up to 2x OU when looking at the supply V x I (fuse) rating
since the depth sounder values are consistently so many times OU it's probably that these are not 'continuous' values
i believe that the depth finding process is pulse driven (like an audio radar) so if the pulse period were, for example, 100ms and the repetition rate was 1 second then all the energy would be compressed into 1/10 of the cycle
the Mfr would be correct in saying that the POWER of the pulse burst used in the system was up to 10 times the supply power
taken over one second, however, the ENERGY of the whole system would still come out underunity
i think this would all be a completely valid approach because i'd imagine that the greater the power of the pulse burst, the better range the system would have
also depth finders can be used to indicate shoals of fish below, and i guess that a higher power would give a greater depth at which you can still detect the fish, so the power would be an important value to know
labelling both RMS & pk-to-pk values, of course, is getting dragged back into the same old marketing ploy used by amp mfrs!
hope this helps
np
http://docsfreelunch.blogspot.com (http://docsfreelunch.blogspot.com)
Does this mean that the 14" fish I caught the other day is really 29"? If so, this is really cool.
Does this company make condoms?
Bill
Quote from: Pirate88179 on July 18, 2011, 01:47:39 AM
Does this mean that the 14" fish I caught the other day is really 29"? If so, this is really cool.
Does this company make condoms?
Bill
LOL
of course, as a fisherman Bill, you'd already know that a 14" fish is always going to get reported as 29"
i don't know whether the same principle also applies in other areas of a fisherman's life! ;)
No OU, it's a foolish advertisement like audio amp, they obviously confound Watts, Watts RMS, Watts peak, and Musical Watts, so you have 4 5 different "Watt" measurements, recently I have bought a 1200 Watts amplifier, with a 200 watts input and a transformer rated at 100 watts (the real input)... ::) :P
Yeah it's funny :D
by the way, if anyone here is in advertising or marketing, kill yourself...
bill hicks on marketing:
http://www.youtube.com/watch?v=gDW_Hj2K0wo
Quote from: Pirate88179 on July 18, 2011, 01:47:39 AM
Does this mean that the 14" fish I caught the other day is really 29"? If so, this is really cool.
Does this company make condoms?
Bill
No Bill I think the way I was seeing their power in / out translation that 14" fish you caught was a 29 foot long fish. LOL
nul-points, Thank you for your explanation. I had a feeling one of the guru's here (and yes I consider you one of them) would come up with a reasonable explanation for this which fits the whole picture. I would have bought the cheap audio amp analogy if it was just some no name companies but this didn't fit my favorite GPS maker Garmin at all. With an enterprise value of $5 Billion I couldn't see them wanting to get caught in a cheap lie about power ratings on fish finders.
I'll consider my mystery solved :)