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L124C 08-30-2012 04:26 PM

Digital vs. Analog engine gauges
 
I'm shopping for gauges for my small Yanmar diesel (Ammeter, Oil pressure, Water Temp and Voltmeter). Most of the gauges I've seen have been analog. Then I found these by Cruz Pro. CruzPro electronic boat instruments, alarms, digital gauges and monitors
My depth, wind speed, boat speed gauges are all digital and I'm wondering why I don't see more digital engine gauges on the market. They seem to cost about three times as much. Other than that, are there any drawbacks?

eherlihy 08-30-2012 04:33 PM

Re: Digital vs. Analog engine gauges
 
<iframe width="560" height="315" src="http://www.youtube.com/embed/il1Byvn_vMA?rel=0" frameborder="0" allowfullscreen></iframe>

Pretty much sums it up....

miatapaul 08-30-2012 07:44 PM

Re: Digital vs. Analog engine gauges
 
Quote:

Originally Posted by L124C (Post 916170)
I'm looking at gauges for my small Yanmar diesel (Ammeter, Oil pressure, Water Temp and Voltmeter). Most of the gauges I've seen have been analog. Then I found these by Cruz Pro. CruzPro electronic boat instruments, alarms, digital gauges and monitors
My depth, wind speed, boat speed gauges are all digital and I'm wondering why I don't see more digital engine gauges on the market. They seem to cost about three times as much. Other than that, are there any drawbacks?

I like analog engine gauges as I can glance at them and tell if I am where I should be. I don't really care what my exact oil pressure is to the 10th of a PSI, I want to know if I have pressure and if it is about where it was yesterday.

Batteries on the other hand I like digital, as there a tenth of a volt is important and you can't see that accurately on an analog gauge. So there is a place for both.

denverd0n 08-31-2012 09:52 AM

Re: Digital vs. Analog engine gauges
 
Quote:

Originally Posted by miatapaul (Post 916229)
I like analog engine gauges as I can glance at them and tell if I am where I should be.

Exactly. I don't care if my engine temperature is 156 degrees or 157 degrees. I just need to know if it is in the normal range. An analog temp gauge tells me that with a glance (even without my glasses on!), and almost without a thought. That's why I strongly prefer analog gauges for the engine functions.

nickmerc 08-31-2012 11:50 AM

Re: Digital vs. Analog engine gauges
 
Analog also allow you to see trends better. If your oil pressure is falling you can see how fast. If your temp is oscillating (or not) you can see how much. Plus, I have organized mine so that when everything is normal at my cruising rpm all of the needles line up. I can then quickly see if anyting is amiss.

hellosailor 08-31-2012 08:34 PM

Re: Digital vs. Analog engine gauges
 
"why I don't see more digital engine gauges on the market. "
Because the analog guages are all pretty much just voltmeters and voltmeters are cheap. And in the aftermath of Three Mile island (really) a lot of research was done about guages and humans watching them.
A digital disaply requires a brain to process the numbers and some attention to them. An analog display just requires pattern recognition, which the mind does at a much lower faster level. i.e. "The needle should be THERE" and when the folks who install the guages do their job properly, all the needles will be pointing the same way when things are normal, so all your eye has to see is "Hey, that one's different" to spot a problem.
Really. That's why you'll oftne see race cars with the tach "twisted" to some odd position, so the needle is pointing "there" when everything is right, as opposed to always being oriented like a clock face.

Cheaper, more effective. And more waterproof too, I'd bet.

L124C 09-01-2012 01:49 AM

Re: Digital vs. Analog engine gauges
 
Quote:

Originally Posted by hellosailor (Post 916602)
"why I don't see more digital engine gauges on the market. "
Because the analog gauges are all pretty much just voltmeters and voltmeters are cheap. And in the aftermath of Three Mile island (really) a lot of research was done about gauges and humans watching them.
A digital display requires a brain to process the numbers and some attention to them. An analog display just requires pattern recognition, which the mind does at a much lower faster level. i.e. "The needle should be THERE" and when the folks who install the gauges do their job properly, all the needles will be pointing the same way when things are normal, so all your eye has to see is "Hey, that one's different" to spot a problem.
Really. That's why you'll oftne see race cars with the tach "twisted" to some odd position, so the needle is pointing "there" when everything is right, as opposed to always being oriented like a clock face. Cheaper, more effective. And more waterproof too, I'd bet.

Interesting. Had never thought of installing them in a similar optimal position, and it makes sense. Don't know about the waterproof issue though...As I said, all my other gauges are digital. They are fully exposed to weather and have performed without a hitch for at least 7 years.

hellosailor 09-01-2012 12:09 PM

Re: Digital vs. Analog engine gauges
 
"Had never thought of installing them in a similar optimal position."
Part of the studies, and I totally forget who did them but something about a British power company comes to mind, eventually concluded that the best guages were the "edge on" type analog ones. That is, a vertical rectangle, not a round guage. And having the needle go "up and down" instead of around like a clock. That design is rare in consumer products, except for old-fashioned boat voltmeters. But the concept is that if the entire SYSTEM is designed properly, all the needles will normally be halfway up the display, so if you've got a wall full of them to monitor, you just have to pass your eyes over them and see "everything the same" in the middle of all the displays, and you know everything is OK.
Which is why Homer Simpson is so good at his job.<G>

Twisting the guages is what one does when one can't design the entire system, but has to work with whatever was in stock at the store.

The other rawback to digital is simply trying to read them. LCD? You can read in daylight, if polarized glasses aren't a problem. Can't read it at night without illumination, which consumes power or burns out. LED? Yeah, great at night but can't see it during the day, burns even more power. Anything else? Pricey! So...sometimes obsolete needles aren't such a ba way to go.

L124C 09-03-2012 07:59 PM

Re: Digital vs. Analog engine gauges
 
Contacted Cruz Pro regarding several issues. Their response was interesting:

"Our digital gauges all have built in user-settable low and high alarms so your existing alarm senders become redundant. You may find that you can replace the existing ON/OFF senders with proper resistive senders and screw them into the same fittings as the existing alarm senders.

To display alternator output you need to be able top place a current shunt in the negative leg of the alternator. This is easy If your alternator has a floating negative output but very difficult if your alternator negative is connected to the alternator case. The CruzPro A60 (CruzPro A30 Digital Amps Gauge) is the only digital ammeter that we manufacture. Some of our battery monitors such as the VAH60, VAH65 and VAH110 also have a built-in ammeter function as well as the voltmeters.

The current that our LCD voltmeters draw is very low however (only about 0.035 amps) at maximum backlight intensity. Even a small 90 amp 12V battery would run the voltmeter for months."

So it seems the current draw isn't an issue. I could set an alarm on the AMP and Volt meter to alert me when the current dropped below a certain level. Seems even more fool proof than aligning the analog needles. Not clear on the "floating negative output" I think my alternator has a negative wire. Anyone know for a Yamar 2GM20?

hellosailor 09-03-2012 10:57 PM

Re: Digital vs. Analog engine gauges
 
"So it seems the current draw isn't an issue."
Not with an LCD that has no backlight. A backlight can pull 40-120mA all by itself, way way more than the LCD does.

"I could set an alarm ...Seems even more fool proof than aligning the analog needles."
Depends on the quality of the fool. (G) An analog needle relies on someone looking at it. Digital alarms involve whether you can hear the alarm over engine and background noises, and multiple stages of electronics and wiring that can all fail. Foolproof? I'd suggest the digital and the alarms require less attention, but they've got more ways to fail. Or, more ways to get your attention.

"Not clear on the "floating negative output" they're looking for an alternator which is NOT grounded to the engine block, but has a separate negative lead. Don't know what you've got. AFAIK there should be no reason why they need to install the current shunt in the negative versus positive line, since a shunt works the same way in either location, and the polarity of the voltage drop across the shunt doesn't matter. I would guess that because of the way they have set up their alarm circuits, they've painted themselves into a corner requiring the shunt to be installed in the negative lead. It shouldn't (dirty word) be that hard for them to design a circuit that can be used in either side, positive or negative. You see the avantage of fancy digital electronics now, huh? (G)


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