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Voltmeter & Ammeter normal ranges

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cluros(at)gmail.com
Guest

Posted: Sat Sep 23, 2017 3:11 pm Post subject: Voltmeter & Ammeter normal ranges

I am doing the test flying on a friend's RV-6 and as part of the preparation I set up the engine monitor (Dynon 120) to display the following on the voltmeter and ammater:



Voltmeter: Red below 10V, Yellow 10-13.8V, Green 13.8V-14.5V, Red > 14.5V

Ammeter (wired to show current flow in to the batter): Red < 0A, Green 0 - 5A, Yellow 5-30A, Red > 30A.

Battery is an Odyssey PC680 AGM. Alternator and regulator unknown, came with the kit from Van's 10-20 years ago. My guess is Plane Power.

First Question: Do the ammeter settings seem reasonable? Obviously any discharge (<0A) is red as indicative of a problem that requires landing ASAP. Normal charge after a start has been observed to be < 5A within a minute after start, a hard start or low battery would obviously make this worse so I set green as 0-5A but don't have any good basis for this. Same for the yellow and red bands. I want the yellow band to indicate that a long time in this area is a problem, and red to be an immediate problem. Normally once the battery has been charged after a start the value should be zero so perhaps the green band should be 0-1A? What charge level going into this battery would indicate an immediate problem (red band)?

\

After first flight the low current alarm was constantly going off so I changed it from <0 to <1. Second flight had similar but not as frequent problem so I was going to lower it a little more but then I was able to download the engine monitor data to Savvy and WOW is it fantastic being able to look at graphs of engine data. I have no idea what normal would look like but here is a snap shot of the second flight:



You can see the battery amps wander between -2 to +2, with excursions to -3 +3 later in the flight (during large engine power changes).

Second Question: Is this behaviour indicative of:

A. Normal operation

B. Sensor problem

C. Charging system or battery problem

D. Something else

Thank you all for your input.

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user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Sat Sep 23, 2017 3:47 pm Post subject: Re: Voltmeter & Ammeter normal ranges

My D-180 ammeter varies up and down to unreasonable numbers.

I disconnected the shunt and put a jumper directly across the plus

and minus input on the D-180.  One would expect the D-180 to

display 0 amps.  But no, it still varies up and down, not as bad as

before, but still plus and minus 15 or 20 amps.  I believe it is a

software problem.  Maybe the Dynon 120 has the same problem.

_________________
Joe Gores

ceengland7(at)gmail.com
Guest

Posted: Sat Sep 23, 2017 4:13 pm Post subject: Voltmeter & Ammeter normal ranges

On 9/23/2017 6:09 PM, Sebastien wrote:

 	  Quote: 	
		   I am doing the test flying on a friend's RV-6 and as part of the 

 preparation I set up the engine monitor (Dynon 120) to display the 

 following on the voltmeter and ammater:



 Voltmeter: Red below 10V, Yellow 10-13.8V, Green 13.8V-14.5V, Red > 14.5V

 Ammeter (wired to show current flow in to the batter): Red < 0A, Green 

 0 - 5A, Yellow 5-30A, Red > 30A.



 Battery is an Odyssey PC680 AGM. Alternator and regulator unknown, 

 came with the kit from Van's 10-20 years ago. My guess is Plane Power.



 First Question: Do the ammeter settings seem reasonable? Obviously any 

 discharge (<0A) is red as indicative of a problem that requires 

 landing ASAP. Normal charge after a start has been observed to be < 5A 

 within a minute after start, a hard start or low battery would 

 obviously make this worse so I set green as 0-5A but don't have any 

 good basis for this. Same for the yellow and red bands. I want the 

 yellow band to indicate that a long time in this area is a problem, 

 and red to be an immediate problem. Normally once the battery has been 

 charged after a start the value should be zero so perhaps the green 

 band should be 0-1A? What charge level going into this battery would 

 indicate an immediate problem (red band)?

 \

 After first flight the low current alarm was constantly going off so I 

 changed it from <0 to <1. Second flight had similar but not as 

 frequent problem so I was going to lower it a little more but then I 

 was able to download the engine monitor data to Savvy and WOW is it 

 fantastic being able to look at graphs of engine data. I have no idea 

 what normal would look like but here is a snap shot of the second flight:



 You can see the battery amps wander between -2 to +2, with excursions 

 to -3 +3 later in the flight (during large engine power changes).



 Second Question: Is this behaviour indicative of:



 A. Normal operation

 B. Sensor problem

 C. Charging system or battery problem

 D. Something else



 Thank you all for your input.

Well, here's my 2 volts...
	




Current readings depend on where the sensor is located in the system. 

Assuming it's between the battery lead & the bus, it will show charge 

for at least a short time after engine start, to replenish the battery. 

After that, it should show more or less zero (with some slight 

variation) because the alternator has fully charged the battery (no more 

electrons flowing into the battery) and is supplying all the electron 

needs of the avionics, etc. It would show discharge whenever the 

alternator couldn't keep up with the load demands of the a/c, and the 

battery started picking up the balance of the demand. (Shouldn't happen 

unless you've intentionally undersized the alternator to save weight, 

and are willing to accept temporary discharge during very short term 

events like landing lights, gear extension/retraction, etc.) Other time 

you'd see it is if the charging system is failing or has failed.



But I don't even have an ammeter on my current plane, & don't plan to 

install one in the plane I'm building. Alternator voltage gives all info 

needed during flight.



Voltage: At 10 volts, the battery is effectively dead, and you might not 

see *any* indication from the EFIS engine monitor (or from the EFIS 

itself). If I were setting limits, I'd realize that anything under 

around 12.5 volts means the charging system is effectively dead (red). 

I'd probably set the red limit even higher; around 13.5, because I'd 

want to know instantly that I've lost charging. I'd only see the yellow 

band as useful to show intermittent excess demand situations, where it 

would go in & out of yellow as really big loads were exceeding the 

alternator's capacity. So yellow from around 13.5 to just under that 

particular alternator's 'normal' output voltage, which hopefully, is 

over 14.3 or so to keep the AGM battery fully charged. Red again above 

about 14.8 or so, since Odyssey says 14.7 is a safe level of initial 

charge voltage.



Hope its at least worth what you paid...



Charlie



---

This email has been checked for viruses by Avast antivirus software.

https://www.avast.com/antivirus

cluros(at)gmail.com
Guest

Posted: Sat Sep 23, 2017 6:01 pm Post subject: Voltmeter & Ammeter normal ranges

Very interesting Joe, thanks for the reply. Did you try upgrading the firmware? Did you follow up with Dynon about this behaviour? In view of your experience I think I'll give them a call on Monday. 



Sebastien



 	  Quote: 	
		   On Sep 24, 2017, at 01:47, user9253 <fransew(at)gmail.com> wrote:

 

 

 

 My D-180 ammeter varies up and down to unreasonable numbers.  I disconnected the shunt and put a jumper directly across the plus and minus input on the D-180.  One would expect the D-180 to display 0 amps.  But no, it still varies up and down, not as bad as before, but still plus and minus 15 or 20 amps.  I believe it is a software problem.  Maybe the Dynon 120 has the same problem.

 

 --------

 Joe Gores

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=473105#473105

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Sat Sep 23, 2017 6:16 pm Post subject: Re: Voltmeter & Ammeter normal ranges

Yes, the D-180 firmware is up to date.  No, I did not contact Dynon.  The ammeter function is not important to me.  I agree with Charlie, the voltmeter tells me how the charging system is working.

_________________
Joe Gores

ashleysc(at)broadstripe.n
Guest

Posted: Sat Sep 23, 2017 6:52 pm Post subject: Voltmeter & Ammeter normal ranges

Hi Sebastien;



Flow out of the battery is not abnormal and will happen whenever your aircraft consumes more power than its alternator can generate. It is not generally a signal to land immediately, but to reduce power consumption (like turn off the landing lights).

Cheers!   Stu.

From: "Sebastien" <cluros(at)gmail.com>

To: aeroelectric-list(at)matronics.com

Sent: Saturday, September 23, 2017 4:09:48 PM

Subject: Voltmeter & Ammeter normal ranges

I am doing the test flying on a friend's RV-6 and as part of the preparation I set up the engine monitor (Dynon 120) to display the following on the voltmeter and ammater:



Voltmeter: Red below 10V, Yellow 10-13.8V, Green 13.8V-14.5V, Red > 14.5V

Ammeter (wired to show current flow in to the batter): Red < 0A, Green 0 - 5A, Yellow 5-30A, Red > 30A.

Battery is an Odyssey PC680 AGM. Alternator and regulator unknown, came with the kit from Van's 10-20 years ago. My guess is Plane Power.

First Question: Do the ammeter settings seem reasonable? Obviously any discharge (<0A) is red as indicative of a problem that requires landing ASAP. Normal charge after a start has been observed to be < 5A within a minute after start, a hard start or low battery would obviously make this worse so I set green as 0-5A but don't have any good basis for this. Same for the yellow and red bands. I want the yellow band to indicate that a long time in this area is a problem, and red to be an immediate problem. Normally once the battery has been charged after a start the value should be zero so perhaps the green band should be 0-1A? What charge level going into this battery would indicate an immediate problem (red band)?

\

After first flight the low current alarm was constantly going off so I changed it from <0 to <1. Second flight had similar but not as frequent problem so I was going to lower it a little more but then I was able to download the engine monitor data to Savvy and WOW is it fantastic being able to look at graphs of engine data. I have no idea what normal would look like but here is a snap shot of the second flight:



You can see the battery amps wander between -2 to +2, with excursions to -3 +3 later in the flight (during large engine power changes).

Second Question: Is this behaviour indicative of:

A. Normal operation

B. Sensor problem

C. Charging system or battery problem

D. Something else

Thank you all for your input.

cluros(at)gmail.com
Guest

Posted: Sat Sep 23, 2017 8:25 pm Post subject: Voltmeter & Ammeter normal ranges

I'm guessing from some of the responses I'm getting that the picture I attached did not go through. The apparent current flow out of the battery is not from a high load. We're talking a 40-60 amp alternator powering 10 amps worth of instruments and radios. The load cycles from -2 to +2 amps at least 50 times over the course of a 1 hour flight and it's not because someone's hiding under the floorboards flicking the lights on and off .

I'll try attaching the engine analyzer data again tomorrow. I did manage to check a few minutes of data from an identical analyzer in a different aircraft and while it did cycle up and down a bit, it never showed negative. 



Sebastien



On Sep 24, 2017, at 04:50, ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net) wrote:

 	  Quote: 	
		  Hi Sebastien;



Flow out of the battery is not abnormal and will happen whenever your aircraft consumes more power than its alternator can generate. It is not generally a signal to land immediately, but to reduce power consumption (like turn off the landing lights).

Cheers!   Stu.

From: "Sebastien" <cluros(at)gmail.com (cluros(at)gmail.com)>

To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)

Sent: Saturday, September 23, 2017 4:09:48 PM

Subject: Voltmeter & Ammeter normal ranges

I am doing the test flying on a friend's RV-6 and as part of the preparation I set up the engine monitor (Dynon 120) to display the following on the voltmeter and ammater:



Voltmeter: Red below 10V, Yellow 10-13.8V, Green 13.8V-14.5V, Red > 14.5V

Ammeter (wired to show current flow in to the batter): Red < 0A, Green 0 - 5A, Yellow 5-30A, Red > 30A.

Battery is an Odyssey PC680 AGM. Alternator and regulator unknown, came with the kit from Van's 10-20 years ago. My guess is Plane Power.

First Question: Do the ammeter settings seem reasonable? Obviously any discharge (<0A) is red as indicative of a problem that requires landing ASAP. Normal charge after a start has been observed to be < 5A within a minute after start, a hard start or low battery would obviously make this worse so I set green as 0-5A but don't have any good basis for this. Same for the yellow and red bands. I want the yellow band to indicate that a long time in this area is a problem, and red to be an immediate problem. Normally once the battery has been charged after a start the value should be zero so perhaps the green band should be 0-1A? What charge level going into this battery would indicate an immediate problem (red band)?

\

After first flight the low current alarm was constantly going off so I changed it from <0 to <1. Second flight had similar but not as frequent problem so I was going to lower it a little more but then I was able to download the engine monitor data to Savvy and WOW is it fantastic being able to look at graphs of engine data. I have no idea what normal would look like but here is a snap shot of the second flight:



You can see the battery amps wander between -2 to +2, with excursions to -3 +3 later in the flight (during large engine power changes).

Second Question: Is this behaviour indicative of:

A. Normal operation

B. Sensor problem

C. Charging system or battery problem

D. Something else

Thank you all for your input.

andymeyer

Joined: 31 Mar 2015
Posts: 54
Location: SW MI

Posted: Sun Sep 24, 2017 1:34 am Post subject: Re: Voltmeter & Ammeter normal ranges

Are your lines to/from the shunt twisted pair? If not, you may be getting loop current from elsewhere in the system. Not sure how much, but worth a check.

cluros(at)gmail.com
Guest

Posted: Sun Sep 24, 2017 4:38 am Post subject: Voltmeter & Ammeter normal ranges

They aren't my lines but I'll check . I'm also going through the install manual for the 120 and looking for documentation on the alternator and voltage regulator. Thanks for the idea Andy.



Sebastien



 	  Quote: 	
		   On Sep 24, 2017, at 11:34, andymeyer <ameyer(at)mil-amax.com> wrote:

 

 

 

 Are your lines to/from the shunt twisted pair? If not, you may be getting loop current from elsewhere in the system. Not sure how much, but worth a check.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=473114#473114

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Sun Sep 24, 2017 4:54 am Post subject: Re: Voltmeter & Ammeter normal ranges

As long as system voltage is above 13, it is impossible for current to flow out of the battery.

_________________
Joe Gores

ceengland7(at)gmail.com
Guest

Posted: Sun Sep 24, 2017 5:28 am Post subject: Voltmeter & Ammeter normal ranges

I did get the pic, but honestly didn't pay any attention to it. Just took a look. Note that voltage never drops below 14V. So the charging system is working great. My personal opinion is that you have too much of the wrong information, and not enough needed information. 



Where is the shunt wired into the system?

Is it really a shunt, or a hall effect sensor?

What does the current do with *all loads except the battery removed*? (Yeah, I know you can't do that since the monitor is embedded in the EFIS.) How about with everything turned off except the EFIS/monitor?

A typical shunt has, IIRC, a 50 millivolt full scale output to the meter. Assuming it's a 60A shunt the output at the currents you're measuring would be wandering around a few thousandths of a volt. That is a very small signal, and as others have hinted, relatively easy to impress noise onto the lines. And the most minute variations in resistance of any connection anywhere in the sense circuit could cause large variations in voltage at the meter.

I seriously doubt that there's anything wrong with the charging system. There *may* be issues with the sensor and/or its wiring, but if it were my plane, I'd almost feel like I was getting too much knowledge for my own good. 

On Sat, Sep 23, 2017 at 11:14 PM, Sebastien <cluros(at)gmail.com (cluros(at)gmail.com)> wrote:

 	  Quote: 	
		  I'm guessing from some of the responses I'm getting that the picture I attached did not go through. The apparent current flow out of the battery is not from a high load. We're talking a 40-60 amp alternator powering 10 amps worth of instruments and radios. The load cycles from -2 to +2 amps at least 50 times over the course of a 1 hour flight and it's not because someone's hiding under the floorboards flicking the lights on and off .

I'll try attaching the engine analyzer data again tomorrow. I did manage to check a few minutes of data from an identical analyzer in a different aircraft and while it did cycle up and down a bit, it never showed negative. 



Sebastien



On Sep 24, 2017, at 04:50, ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net) wrote:

 	  Quote: 	
		  Hi Sebastien;



Flow out of the battery is not abnormal and will happen whenever your aircraft consumes more power than its alternator can generate. It is not generally a signal to land immediately, but to reduce power consumption (like turn off the landing lights).

Cheers!   Stu.

From: "Sebastien" <cluros(at)gmail.com (cluros(at)gmail.com)>

To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)

Sent: Saturday, September 23, 2017 4:09:48 PM

Subject: Voltmeter & Ammeter normal ranges

I am doing the test flying on a friend's RV-6 and as part of the preparation I set up the engine monitor (Dynon 120) to display the following on the voltmeter and ammater:



Voltmeter: Red below 10V, Yellow 10-13.8V, Green 13.8V-14.5V, Red > 14.5V

Ammeter (wired to show current flow in to the batter): Red < 0A, Green 0 - 5A, Yellow 5-30A, Red > 30A.

Battery is an Odyssey PC680 AGM. Alternator and regulator unknown, came with the kit from Van's 10-20 years ago. My guess is Plane Power.

First Question: Do the ammeter settings seem reasonable? Obviously any discharge (<0A) is red as indicative of a problem that requires landing ASAP. Normal charge after a start has been observed to be < 5A within a minute after start, a hard start or low battery would obviously make this worse so I set green as 0-5A but don't have any good basis for this. Same for the yellow and red bands. I want the yellow band to indicate that a long time in this area is a problem, and red to be an immediate problem. Normally once the battery has been charged after a start the value should be zero so perhaps the green band should be 0-1A? What charge level going into this battery would indicate an immediate problem (red band)?

\

After first flight the low current alarm was constantly going off so I changed it from <0 to <1. Second flight had similar but not as frequent problem so I was going to lower it a little more but then I was able to download the engine monitor data to Savvy and WOW is it fantastic being able to look at graphs of engine data. I have no idea what normal would look like but here is a snap shot of the second flight:



You can see the battery amps wander between -2 to +2, with excursions to -3 +3 later in the flight (during large engine power changes).

Second Question: Is this behaviour indicative of:

A. Normal operation

B. Sensor problem

C. Charging system or battery problem

D. Something else

Thank you all for your input.

cluros(at)gmail.com
Guest

Posted: Sun Sep 24, 2017 5:36 am Post subject: Voltmeter & Ammeter normal ranges

Exactly. Joe could you please confirm that the jpeg below is visible? If so it's obvious that while the voltage seems to be moving around a tiny bit, it never gets to the point which would allow the amperage shown. It's always above 14V. Also I checked some data with the engine shut down and while the amperage still wanders around it's 1 A or less (-5.5 to -6.5 A)



On Sun, Sep 24, 2017 at 5:54 AM, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:

 	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

 

 As long as system voltage is above 13, it is impossible for current to flow out of the battery.

 

 --------

 Joe Gores

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=473122#473122

 

 

 

 

 

 

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Sep 24, 2017 5:59 am Post subject: Voltmeter & Ammeter normal ranges

At 06:09 PM 9/23/2017, you wrote:

  	  Quote: 	
		  I am doing the test flying on a friend's RV-6 and as part of the preparation I set up the engine monitor (Dynon 120) to display the following on the voltmeter and ammater:



 Voltmeter: Red below 10V, Yellow 10-13.8V, Green 13.8V-14.5V, Red > 14.5V

 Ammeter (wired to show current flow in to the batter): Red < 0A, Green 0 - 5A, Yellow 5-30A, Red > 30A. 	


   Assuming you do monitor bus voltage and have

   active notification of low voltage, then there

   is no operational value for monitoring battery

   current.



   Battery ammeters in airplanes were a carry-over

   from the terrestrial vehicles where the minus-zero-plus

   instrument in the battery charge/discharge line

   was the simplest single monitor of system health

   during normal vehicle operations.



   The ammeter would be expected to show a heavy

   recharge rate right after cranking the engine . . .

   or after a jumper cable start on a dead battery.



   After some interval of normal operation, the battery

   accepts less and less recharge energy and the needle

   migrates toward zero. Under normal ops (votlage about

   right, battery charged) the needle would rest at or

   just slightly above zero.



   If generator output was insufficient (low engine rpm,

   high system loads, regulator voltage drifting downward,

   generator failing) the needle would present some

   value below zero.



   While truly an analog instrument, its BEHAVIOR was

   closer to 'digital' in that it was never intended to

   be READ so much as observed as a go/no-go panel

   instrument.



   Ammeters of all types are of little to no value as sources of

   operational data in flight. Ammeters in the battery

   lead are pretty much useless when compared to an accurate

   voltmeter paired with active notification of low

   voltage.



   Calibrating a battery ammeter with alarm settings

   will be an exercise in futility.



   Suggest you move the ammeter sensor to the alternator

   b-lead and eliminate any alarm functions from this

   reading. The ammeter is most useful as a maintenance

   tool for diagnosing why the VOLTAGE is low and/or

   the LOW VOLTS warning light was illuminated in the

   air. 



 

   Bob . . .

cluros(at)gmail.com
Guest

Posted: Tue Sep 26, 2017 7:18 pm Post subject: Voltmeter & Ammeter normal ranges

Thank you all for your input. I've eliminated the warning function and changed the ammeter band to green only. No more annoying warnings! Well, we still have very high CHT warnings but we have a plan to deal with that. These recording engine monitors sure make it easy to test a new plane. You can concentrate on working the problem without worrying about recording which cylinder was the highest or lowest or whatever the issue may be. 

Biggest lesson learned here is that for future early flights only critical items will have warnings enabled. Today I went along with a friend for moral support on his first flight in his new (to him) Searey Amphibian after a year of repairs and improvements. The previous owner thoughtfully included a switch for turning on or off the audio warnings from the engine monitor. I turned it off for takeoff and sure enough, the bloody thing lit up like Apollo 12 but my buddy climbed straight ahead ignoring everything while I cancelled one spurious warning after another. Not sure he would have been able to be so disciplined if it had been yelling in our ears. 



Sebastien



On Sep 24, 2017, at 09:57, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		    At 06:09 PM 9/23/2017, you wrote:

  	  Quote: 	
		  I am doing the test flying on a friend's RV-6 and as part of the preparation I set up the engine monitor (Dynon 120) to display the following on the voltmeter and ammater:



 Voltmeter: Red below 10V, Yellow 10-13.8V, Green 13.8V-14.5V, Red > 14.5V

 Ammeter (wired to show current flow in to the batter): Red < 0A, Green 0 - 5A, Yellow 5-30A, Red > 30A. 	


   Assuming you do monitor bus voltage and have

   active notification of low voltage, then there

   is no operational value for monitoring battery

   current.



   Battery ammeters in airplanes were a carry-over

   from the terrestrial vehicles where the minus-zero-plus

   instrument in the battery charge/discharge line

   was the simplest single monitor of system health

   during normal vehicle operations.



   The ammeter would be expected to show a heavy

   recharge rate right after cranking the engine . . .

   or after a jumper cable start on a dead battery.



   After some interval of normal operation, the battery

   accepts less and less recharge energy and the needle

   migrates toward zero. Under normal ops (votlage about

   right, battery charged) the needle would rest at or

   just slightly above zero.



   If generator output was insufficient (low engine rpm,

   high system loads, regulator voltage drifting downward,

   generator failing) the needle would present some

   value below zero.



   While truly an analog instrument, its BEHAVIOR was

   closer to 'digital' in that it was never intended to

   be READ so much as observed as a go/no-go panel

   instrument.



   Ammeters of all types are of little to no value as sources of

   operational data in flight. Ammeters in the battery

   lead are pretty much useless when compared to an accurate

   voltmeter paired with active notification of low

   voltage.



   Calibrating a battery ammeter with alarm settings

   will be an exercise in futility.



   Suggest you move the ammeter sensor to the alternator

   b-lead and eliminate any alarm functions from this

   reading. The ammeter is most useful as a maintenance

   tool for diagnosing why the VOLTAGE is low and/or

   the LOW VOLTS warning light was illuminated in the

   air. 



 

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Oct 05, 2017 9:06 am Post subject: Voltmeter & Ammeter normal ranges

At 08:32 AM 9/24/2017, you wrote:

  	  Quote: 	
		  Exactly. Joe could you please confirm that the jpeg below is visible? If so it's obvious that while the voltage seems to be moving around a tiny bit, it never gets to the point which would allow the amperage shown. It's always above 14V. Also I checked some data with the engine shut down and while the amperage still wanders around it's 1 A or less (-5.5 to -6.5 A) 	


  Digital data acquisition is fraught with

  opportunity for confusion/error.  Depending

  on how the variable is sampled, pre-filtered

  and software filtered, data displayed or plotted

  can take on the appearance of instability.



  Unless you're measuring the output from something

  like a battery . . . or a laboratory power supply,

  the stimulus being observed will have some noise

  on it. This is especially true of signals gathered

  from the DC power system of any vehicle.



  When I'm gathering data on relatively low frequency

  events, my DAS pre-filtering is usually rolled

  off at 10 Hz. Then interpretation software is

  designed to do a 'rolling average' on sampled values.

  For a DAS set up to gather 100 samples/second, we'll

  buffer 16 samples in a memory stack, take the sum

  of those values then divide by 16 for an average

  of that 'packet' of data. When the next sample comes

  in, we add the new value, throw away the oldest value

  and do the average again.



  This pre/post processing of data does a nice job

  of ignoring the high frequency perturbations that

  are riding on top of the value of interest. The

  processed data plots are nice smooth lines that

  are more meaningful.



  I suspect that data plots taken from most

  EIS systems have little pre-processing and no

  post processing . . . so the traces are understandably

  'ragged'. So while the voltage traces might

  be interpreted as 'unstable', it's probable

  that the system is operating normally.



  Just for grins, I took the 'scope out to peek at

  the 14v bus in Dr. Dee's '87 GMC Sierra. With

  the 'scope set to 2.5S/div H and 2V/div V, we

  get the following trace when cranking the engine.

 [img]cid:.0[/img]



   Figure 1.



   Note that battery voltage starts to sag from

   about 12.8 volts but takes a steeper slope

   as the starter contactor is energized followed

   by a profound drop to 8 volts as the contactor

   closes.  A few milliseconds later, the voltage

   rises to about 10v until the engine catches

   approx 1.2S later and the alternator kicks

   in . . . whereupon but bus rises to about

   14.6V



 [img]cid:.1[/img]

   Figure 2.



   In the next plot we see that the bus is 'steady'

   at about 14.7V with the occasional perturbation

   combined with some little 'spikes' with an amplitude

   of 1 to 2 volts.



   To get a closer look at the voltage in the

   next plot, we need to turn up the 'scope sensitivity

   and to to AC coupling:



 [img]cid:.2[/img]

  Figure 3.



  With a vertical scale of 0.5V/div and horizontal

  of 0.05S/div we can get a better look at the 'noise'.

  This particular trace caught a 1.5v transient amongst

  about 10 smaller artifacts.



  We see that even when there are no obvious

  transients, the horizontal line has 'thickness'.

  Zooming in closer:



 [img]cid:.3[/img]

  Figure 4.



  We find that the horizontal line is 'fuzzy' with

  positive and negative going transients on the

  order of 300mV peak.



  Depending on where your digital data acquistion

  system takese a 'snapshot', the sampled votlage

  might appear to 'wobble' by as much as +/-0.5V.



  Spreading out the major transients by a factor

  of 20 . . .



 

 [img]cid:.4[/img]

  Figure 5.



 

  Shows that they're about 400 microSeconds wide. These

  plots offer a small peek into the nature of DC power

  systems on vehicles.  A few weeks ago, a thread on

  another list server offered this image suggesting

  that the full-wave, rectified 3-phase alternator

  would produce wave forms something along these lines . . . 



 [img]cid:.5[/img] 



  Figure 6.



  Theoretically true, but  I've never seen so 'clean'

  a picture in the wild . . . 



  Referring to Mil-Std-704 we learn that DC power systems

  demonstrate a certain amount of noise (distortion)

  under normal conditions. The document cites

  the following plot for a 28v system (cut the

  numbers in half for 14 volts).  



 [img]cid:.6[/img]



   Figure 7.



   Over the range of 1000 Hz (1 milliSecond period) and

   10,000 Hz (100 uSecond), we should expect artifacts

   of noise up to 0.5 VRMS (1.5 volts pk-pk) on a 14V bus.



   Above and below those frequencies, the allowable/exoected

   noise levels fall off. When you hook an oscilloscope to

   the bus, the best you can do is sample small features

   of the noise as illustrated in the first 5 figures. Further,

   you'll never see the pristine plots hypothesized in Figure 6.



   



 [img]cid:.7[/img]

 Figure 8.



   The most significant attribute of a DC power system is VOLTAGE.

   Referring again to Mil-STD-704 we find the plot above. Again,

   cut the voltage levels in half for a 14v system.



   This figure suggests that any voltage vs. time condition

   below the upper trace . . . and above the lower trace . . .

   is a condition to be expected for designing and operating

   appliances powered from the DC system.



   It's my wish that this narrative will give you some tools

   for critical review of any data presented by either operating

   or diagnostic instruments. Understanding characteristics

   signals present on the bus -AND- limits on the measuring

   instrument will go to better design, operation and diagnosis

   of your ship's DC power system.



 

   Bob . . .

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bob.verwey(at)gmail.com
Guest

Posted: Thu Oct 05, 2017 9:05 pm Post subject: Voltmeter & Ammeter normal ranges

Absolutely facinating and insightful to a neophyte like myself <grin>



On 05 Oct 2017 7:17 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote: 	  Quote: 	
		    At 08:32 AM 9/24/2017, you wrote:

  	  Quote: 	
		  Exactly. Joe could you please confirm that the jpeg below is visible? If so it's obvious that while the voltage seems to be moving around a tiny bit, it never gets to the point which would allow the amperage shown. It's always above 14V. Also I checked some data with the engine shut down and while the amperage still wanders around it's 1 A or less (-5.5 to -6.5 A) 	


  Digital data acquisition is fraught with

  opportunity for confusion/error.  Depending

  on how the variable is sampled, pre-filtered

  and software filtered, data displayed or plotted

  can take on the appearance of instability.



  Unless you're measuring the output from something

  like a battery . . . or a laboratory power supply,

  the stimulus being observed will have some noise

  on it. This is especially true of signals gathered

  from the DC power system of any vehicle.



  When I'm gathering data on relatively low frequency

  events, my DAS pre-filtering is usually rolled

  off at 10 Hz. Then interpretation software is

  designed to do a 'rolling average' on sampled values.

  For a DAS set up to gather 100 samples/second, we'll

  buffer 16 samples in a memory stack, take the sum

  of those values then divide by 16 for an average

  of that 'packet' of data. When the next sample comes

  in, we add the new value, throw away the oldest value

  and do the average again.



  This pre/post processing of data does a nice job

  of ignoring the high frequency perturbations that

  are riding on top of the value of interest. The

  processed data plots are nice smooth lines that

  are more meaningful.



  I suspect that data plots taken from most

  EIS systems have little pre-processing and no

  post processing . . . so the traces are understandably

  'ragged'. So while the voltage traces might

  be interpreted as 'unstable', it's probable

  that the system is operating normally.



  Just for grins, I took the 'scope out to peek at

  the 14v bus in Dr. Dee's '87 GMC Sierra. With

  the 'scope set to 2.5S/div H and 2V/div V, we

  get the following trace when cranking the engine.

 [img]cid:.0[/img]



   Figure 1.



   Note that battery voltage starts to sag from

   about 12.8 volts but takes a steeper slope

   as the starter contactor is energized followed

   by a profound drop to 8 volts as the contactor

   closes.  A few milliseconds later, the voltage

   rises to about 10v until the engine catches

   approx 1.2S later and the alternator kicks

   in . . . whereupon but bus rises to about

   14.6V



 [img]cid:.1[/img]

   Figure 2.



   In the next plot we see that the bus is 'steady'

   at about 14.7V with the occasional perturbation

   combined with some little 'spikes' with an amplitude

   of 1 to 2 volts.



   To get a closer look at the voltage in the

   next plot, we need to turn up the 'scope sensitivity

   and to to AC coupling:



 [img]cid:.2[/img]

  Figure 3.



  With a vertical scale of 0.5V/div and horizontal

  of 0.05S/div we can get a better look at the 'noise'.

  This particular trace caught a 1.5v transient amongst

  about 10 smaller artifacts.



  We see that even when there are no obvious

  transients, the horizontal line has 'thickness'.

  Zooming in closer:



 [img]cid:.3[/img]

  Figure 4.



  We find that the horizontal line is 'fuzzy' with

  positive and negative going transients on the

  order of 300mV peak.



  Depending on where your digital data acquistion

  system takese a 'snapshot', the sampled votlage

  might appear to 'wobble' by as much as +/-0.5V.



  Spreading out the major transients by a factor

  of 20 . . .



 

 [img]cid:.4[/img]

  Figure 5.



 

  Shows that they're about 400 microSeconds wide. These

  plots offer a small peek into the nature of DC power

  systems on vehicles.  A few weeks ago, a thread on

  another list server offered this image suggesting

  that the full-wave, rectified 3-phase alternator

  would produce wave forms something along these lines . . . 



 [img]cid:.5[/img] 



  Figure 6.



  Theoretically true, but  I've never seen so 'clean'

  a picture in the wild . . . 



  Referring to Mil-Std-704 we learn that DC power systems

  demonstrate a certain amount of noise (distortion)

  under normal conditions. The document cites

  the following plot for a 28v system (cut the

  numbers in half for 14 volts).  



 [img]cid:.6[/img]



   Figure 7.



   Over the range of 1000 Hz (1 milliSecond period) and

   10,000 Hz (100 uSecond), we should expect artifacts

   of noise up to 0.5 VRMS (1.5 volts pk-pk) on a 14V bus.



   Above and below those frequencies, the allowable/exoected

   noise levels fall off. When you hook an oscilloscope to

   the bus, the best you can do is sample small features

   of the noise as illustrated in the first 5 figures. Further,

   you'll never see the pristine plots hypothesized in Figure 6.



   



 [img]cid:.7[/img]

 Figure 8.



   The most significant attribute of a DC power system is VOLTAGE.

   Referring again to Mil-STD-704 we find the plot above. Again,

   cut the voltage levels in half for a 14v system.



   This figure suggests that any voltage vs. time condition

   below the upper trace . . . and above the lower trace . . .

   is a condition to be expected for designing and operating

   appliances powered from the DC system.



   It's my wish that this narrative will give you some tools

   for critical review of any data presented by either operating

   or diagnostic instruments. Understanding characteristics

   signals present on the bus -AND- limits on the measuring

   instrument will go to better design, operation and diagnosis

   of your ship's DC power system.



 

   Bob . . .

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cluros(at)gmail.com
Guest

Posted: Fri Oct 06, 2017 10:36 am Post subject: Voltmeter & Ammeter normal ranges

Thank you Bob. Very good information and well presented. I'm looking forward to learning more about the capabilities and limits of these instruments.



On Thu, Oct 5, 2017 at 10:03 PM, Bob Verwey <bob.verwey(at)gmail.com (bob.verwey(at)gmail.com)> wrote:

 	  Quote: 	
		  Absolutely facinating and insightful to a neophyte like myself <grin>



On 05 Oct 2017 7:17 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote: 	  Quote: 	
		    At 08:32 AM 9/24/2017, you wrote:

  	  Quote: 	
		  Exactly. Joe could you please confirm that the jpeg below is visible? If so it's obvious that while the voltage seems to be moving around a tiny bit, it never gets to the point which would allow the amperage shown. It's always above 14V. Also I checked some data with the engine shut down and while the amperage still wanders around it's 1 A or less (-5.5 to -6.5 A) 	


  Digital data acquisition is fraught with

  opportunity for confusion/error.  Depending

  on how the variable is sampled, pre-filtered

  and software filtered, data displayed or plotted

  can take on the appearance of instability.



  Unless you're measuring the output from something

  like a battery . . . or a laboratory power supply,

  the stimulus being observed will have some noise

  on it. This is especially true of signals gathered

  from the DC power system of any vehicle.



  When I'm gathering data on relatively low frequency

  events, my DAS pre-filtering is usually rolled

  off at 10 Hz. Then interpretation software is

  designed to do a 'rolling average' on sampled values.

  For a DAS set up to gather 100 samples/second, we'll

  buffer 16 samples in a memory stack, take the sum

  of those values then divide by 16 for an average

  of that 'packet' of data. When the next sample comes

  in, we add the new value, throw away the oldest value

  and do the average again.



  This pre/post processing of data does a nice job

  of ignoring the high frequency perturbations that

  are riding on top of the value of interest. The

  processed data plots are nice smooth lines that

  are more meaningful.



  I suspect that data plots taken from most

  EIS systems have little pre-processing and no

  post processing . . . so the traces are understandably

  'ragged'. So while the voltage traces might

  be interpreted as 'unstable', it's probable

  that the system is operating normally.



  Just for grins, I took the 'scope out to peek at

  the 14v bus in Dr. Dee's '87 GMC Sierra. With

  the 'scope set to 2.5S/div H and 2V/div V, we

  get the following trace when cranking the engine.

 [img]cid:.0[/img]



   Figure 1.



   Note that battery voltage starts to sag from

   about 12.8 volts but takes a steeper slope

   as the starter contactor is energized followed

   by a profound drop to 8 volts as the contactor

   closes.  A few milliseconds later, the voltage

   rises to about 10v until the engine catches

   approx 1.2S later and the alternator kicks

   in . . . whereupon but bus rises to about

   14.6V



 [img]cid:.1[/img]

   Figure 2.



   In the next plot we see that the bus is 'steady'

   at about 14.7V with the occasional perturbation

   combined with some little 'spikes' with an amplitude

   of 1 to 2 volts.



   To get a closer look at the voltage in the

   next plot, we need to turn up the 'scope sensitivity

   and to to AC coupling:



 [img]cid:.2[/img]

  Figure 3.



  With a vertical scale of 0.5V/div and horizontal

  of 0.05S/div we can get a better look at the 'noise'.

  This particular trace caught a 1.5v transient amongst

  about 10 smaller artifacts.



  We see that even when there are no obvious

  transients, the horizontal line has 'thickness'.

  Zooming in closer:



 [img]cid:.3[/img]

  Figure 4.



  We find that the horizontal line is 'fuzzy' with

  positive and negative going transients on the

  order of 300mV peak.



  Depending on where your digital data acquistion

  system takese a 'snapshot', the sampled votlage

  might appear to 'wobble' by as much as +/-0.5V.



  Spreading out the major transients by a factor

  of 20 . . .



 

 [img]cid:.4[/img]

  Figure 5.



 

  Shows that they're about 400 microSeconds wide. These

  plots offer a small peek into the nature of DC power

  systems on vehicles.  A few weeks ago, a thread on

  another list server offered this image suggesting

  that the full-wave, rectified 3-phase alternator

  would produce wave forms something along these lines . . . 



 [img]cid:.5[/img] 



  Figure 6.



  Theoretically true, but  I've never seen so 'clean'

  a picture in the wild . . . 



  Referring to Mil-Std-704 we learn that DC power systems

  demonstrate a certain amount of noise (distortion)

  under normal conditions. The document cites

  the following plot for a 28v system (cut the

  numbers in half for 14 volts).  



 [img]cid:.6[/img]



   Figure 7.



   Over the range of 1000 Hz (1 milliSecond period) and

   10,000 Hz (100 uSecond), we should expect artifacts

   of noise up to 0.5 VRMS (1.5 volts pk-pk) on a 14V bus.



   Above and below those frequencies, the allowable/exoected

   noise levels fall off. When you hook an oscilloscope to

   the bus, the best you can do is sample small features

   of the noise as illustrated in the first 5 figures. Further,

   you'll never see the pristine plots hypothesized in Figure 6.



   



 [img]cid:.7[/img]

 Figure 8.



   The most significant attribute of a DC power system is VOLTAGE.

   Referring again to Mil-STD-704 we find the plot above. Again,

   cut the voltage levels in half for a 14v system.



   This figure suggests that any voltage vs. time condition

   below the upper trace . . . and above the lower trace . . .

   is a condition to be expected for designing and operating

   appliances powered from the DC system.



   It's my wish that this narrative will give you some tools

   for critical review of any data presented by either operating

   or diagnostic instruments. Understanding characteristics

   signals present on the bus -AND- limits on the measuring

   instrument will go to better design, operation and diagnosis

   of your ship's DC power system.



 

   Bob . . .

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