AC/DC Power Monitor?

[rv_safetyman]

Some time back, I started a thread on AC/DC power monitors.  I want to bring it up again and ask for your help.

I really need to revise my AC Power monitor panel (uses two direct reading analog ammeters with 6 gauge wires to each plus two analog voltmeters – not a great design!!)   and I also want a good DC power meter. 

The following would be my ideal monitor:

    -   three each AC ammeters (two legs of 240 and the one leg from the inverter)
    -   voltage for each AC line
    -   frequency for each AC line
    -   high current (500A?) DC ammeter (from house battery bank to inverter)
    -   one or two lower current (200A?) DC ammeter(s) for DC circuits in cabin and/or engine alternator.
    -   DC voltage for each of the DC circuits noted above
    -   State of charge meter
    -   All readouts would be on an LCD display

I can go one of two routes.  If someone can point me to a good system, I will consider buying it.  If there is nothing out there, I will strongly consider developing one.

Here is what I have found so far:

http://vena.com  used to make a meter with one AC and 2 DC meters.  They no longer list it on their website.

http://www.wholesalesolar.com/meters.html  They carry the Trace TM500A and The TryMetric 2020.  Both seem to be good "state of charge" meters, but do not cover my AC needs

The fellow who helped me develop my fire detection system is more that willing to develop a meter with all of the capabilities listed above.  We have a preliminary design concept in place.

So, I need your help. 

First, let me know if there is something out there that will come close to doing what I need. 

OR

Give me some input on designing a new meter.  You can do that via a reply here for all to see, or contact me off line:

jim At rvsafetysystems *dot* com
three zero three 478 – 3501

Thanks.

[Ross]

This would be my ideal all-in-one meter....although I probably couldn't afford to buy it.

AC - Two digital volt meters and two digital ammeters.  One for each incoming leg.

DC - This should be pretty much a copy of the Trimetric.  It should show volts, amps, percent left in battery bank, etc.

There should be an AC module that would connect to the AC legs in a convenient location, a DC module that would also go in a convenient location and a remote that would connect to both modules via CAT5 cable or something similar.   

Ross

[TomCat]

Although you have to use it with certain Xantrex products, this panel does what you want...Only two incoming AC legs though. Connects with CAT5 cables.

http://www.xantrex.com/web/id/86/p/1/pt/7/product.asp

Jay
87 SaftLiner

[Ross]

I have that remote on my inverter.  It's not bad.  If it read the battery bank in percent, I'd be happy with it.  It does give more information than most inverter remotes though.  All I really need is a Trimetric to handle the DC, but they are expensive.

Ross

[pvcces]

Jim, one thing that you didn't mention is that all you need to read all of the currents and voltages is one or more accurate voltmeters. To get the current readings, either AC or DC, use a shunt in the line that is carrying the load.

With the cost of new cables as high as it has gotten to be, cutting into the amount of heavy cables is a real cost saver. The small wires between the shunts and the meter should be in twisted pairs, so that electrical noise will not be able to throw them off.

For what it's worth.

Tom Caffrey

[Jeremy]

I've bought a couple of these for my bus, so I can measure the load on the inverter and generator circuits and switch between the two if required:



Obviously they are designed to be plugged straight into a mains electrical socket, but when I install them in the bus I intended to effectively hardwire them into the circuit with the 'socket' part hidden and the LCD displays at eye-level mounted in a panel inside the bus along with the various other electrical gubbins (switches, tank monitors etc).

The devices will measure voltage (V), amps (A), watts (W), volt-amps(VA), hertz (Hz) and power factor (PF). One neat function it has got is a buzzer alarm when the current load on the circuit reaches a certain point - so I can be sure of never overloading the inverter (although the inverter is supposed to be proof against that anyway). You would still need somthing else for the DC side, but these things seemed to be a good (and very cheap) option to the various specialist RV power panels available. Obviously this particular unit is of no use to you as it is for UK 240v AC, but there are almost certainly 110v versions available

Just an idea for what it's worth

Jeremy

[Sean]

Jim,

These are pricey, but they do what you want:

AC:
http://www.bluesea.com/product.asp?Product_Id=25863&d_Id=7485&l1=7461&l2=7485

DC:
http://www.bluesea.com/product.asp?Product_Id=25876&d_Id=7485&l1=7461&l2=7485

If you get one of each, plus additional shunts and current transformers, you can make a switch setup to monitor as many different sources as you'd like.

Blue Sea also has circuit panels with these meters, and appropriate switches, built in.

FWIW, I would just buy current transformers for each AC leg you want to monitor (sounds like three, although you might want one for the neutral as well), shunts for the DC loads, a digital mV meter, and the correct resistors to make the mV meter read direct in amps and volts, then put a 12-pole rotary switch on the deal to select the reading you want.  You'd need to get a separate meter, then, for the frequency, although I suspect your inverter can provide that for you.

-Sean

[DrivingMissLazy]

then put a 12-pole rotary switch on the deal to select the reading you want.

Be very careful in selecting the switch. There are special rotary switches made for this application and you must use one of them.
The reason, when switching between current transformers (CT's) for measuring amps,  the switch contacts must be a make before break arrangement.
Richard

[Gary '79 5C]

I use a Newmar ( marine use design) in my bus and it is quite similiar to your wants. The amp meter for the two 120 legs use the same meter with a switch. Saves panel space that way. It has been bulletproof. Newmar can be pricey ( No, Really Pricey) but for the long haul It is a great product.
Richard is very correct with the make before break switch for CT's. They will not work after you let the smoke out....

Good Luck

[Sean]

I should have mentioned the make-before-break requirement, for the benefit of the group.  I knew, though, that Jim already knew that...

-Sean

[DrivingMissLazy]

I should have mentioned the make-before-break requirement, for the benefit of the group.  I knew, though, that Jim already knew that...

-Sean

Isn't Jim the one who run #6 guage wire for his ammeters? I wonder where he found direct reading ammeters for 50 or 75 amps?
Richard

[Sean]

...  I wonder where he found direct reading ammeters for 50 or 75 amps?

Lots of 'em available, especially for automotive DC applications.  One that I had looked at for AC is here:
http://www.surplussales.com/Meters/MtrACAmps.html

[Scroll down to (MTR) 409C676A34]

Plenty of inexpensive AC switchgear incorporates "direct-read" meters at 50 to 100 amps.  These are cheap shunt-type meters with simple movements, and, of course, are merely "calibrated" for AC.  Surplus meters from these applications are generally pennies on the dollar.  FWIW.

[David Anderson]

Jim,  Here is my post on the ammeter installation.  It's not all you want, but it has been very helpful to me to see what my genny is doing since I can see it while driving.  We may have actually discussed this before, but I can't remember.  I highly recommend current tranformers over the #6 cable running through the ammeter.

Since I have a Trace SW2512 I can monitor all my battery usage and AC power through the inverter through the display panel (on the inverter leg only).   It doesn't show DC amps but battery voltage, not quite what you want, but gives me all the monitoring I need.

David

http://www.busnut.com/bbs/messages/233/5416.html

[DrivingMissLazy]

...  I wonder where he found direct reading ammeters for 50 or 75 amps?

Lots of 'em available, especially for automotive DC applications.  One that I had looked at for AC is here:
http://www.surplussales.com/Meters/MtrACAmps.html

[Scroll down to (MTR) 409C676A34]

Plenty of inexpensive AC switchgear incorporates "direct-read" meters at 50 to 100 amps.  These are cheap shunt-type meters with simple movements, and, of course, are merely "calibrated" for AC.  Surplus meters from these applications are generally pennies on the dollar.  FWIW.

Yep, you're correct. I do not ever remember seeing anything like this in my 50 years of building higher powered electrical equipment. The only thing that I remember is the 25-0-25 direct reading DC ammeter on my Model A Ford.
Richard

[ChuckMC9]

Seems to me that something like this screams for a 'black box' solution that is direct connected or networked or bluetoothed to a computer, with an application running on the computer for display. Extra points for ability to take a snapshot for the webserver.

I have been wanting a subset of what is being described, at the least a Trimetric with independent displays, rather than fiddling with buttons. I want everything in one view, no touching req'd.

Will be following this with interest, and if you design something custom, Jim, make it repeatable and manufacturable! (or 'riggable' )