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.
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
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
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
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
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:
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fwww.maplin.co.uk%2Fimages%2F300%2FL61aq.jpg&hash=b78f4da34387130457a3810907c087affaaac460)
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
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
Quote from: Sean on January 14, 2007, 10:40:19 AM
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
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
I should have mentioned the make-before-break requirement, for the benefit of the group. I knew, though, that Jim already knew that...
-Sean
Quote from: Sean on January 14, 2007, 03:42:26 PM
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
Quote from: DrivingMissLazy on January 14, 2007, 04:50:23 PM
... 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.
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
Quote from: Sean on January 14, 2007, 07:24:49 PM
Quote from: DrivingMissLazy on January 14, 2007, 04:50:23 PM
... 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
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' ;))
Wow, what good input!
Off line, I was informed that Vena still makes their monitor and it is apparently sold at Camping World ($299).
It would appear that there are several solutions that are at least close to what I would like to do.
I have not had time to look at the details of each system. I will do that over the next few days (currently thrashing to get to Quartzsite tomorrow). Also, my so called broadband with the DataStorm is terrible at night (upgrading this week)
David, I had forgotten about your system. I will look close at that, since the meters will probably match my present Shurite analog AC volt meters
Chuck, you always think out of the box. Your approach sounds a bit like the SilverLeaf VMSpc system that uses a PC to display all of the electonic engine data. Great Idea. May give that some further thought.
I suspect that cooler heads will prevail and I will not take on a new project. The market would probably not justify the development costs. However, it is sure fun to think about what an "ideal" meter would look like and how it would function.
Jim, did you ever build or buy one of these?
I want one!
Hi Chuck. Wow, I about died when I saw this old thread crop up again.
I ended up with the TriMetric unit (http://www.bogartengineering.com/). I am quite pleased with the unit. I am still doing some playing with the constants you have to put in. I like the ammeter function as it give me the net current delivered to (or drawn from) the house battery bank. Some of those numbers really drive home what the big current items are (we know general concepts, but having real data really drive home the impact).
Since I started that thread, I have added a separate alternator for the house batteries and some solar panels. That really make reading the ammeter interesting!
I am a data junkie, so the gauge is really fun for me as well as providing good information.
For those of you just now reading this thread, I got started wanting to know the battery "state of charge". If you do any reading on the subject, you will see that there is no good way to really check that value other than a good integrating ammeter system. Voltage is not a very good way of "measuring" SOC. It only works if the battery has not be charged or discharged over a several hour period and that does not happen with our systems. A hydrometer is about as good as you can get with out buying a "computer" system.
As I reviewed the old thread, I noticed that my 110V ammeter system came up. I have since changed from two direct reading ammeters to two shut type ammeters. I just did not like the risk of running high current circuits up to the electrical panel.
Jim
Thanks for the update, Jim! I brought this back up because I recently had some power challenges and doing some real monitoring is definitely getting moved up in the project list.
I have imagined that I would end up doing exactly what you have - a Trimetric + AC gauges. Would still love to have something like you first described, but life's too short, eh? It's also good to hear that you redid the AC ammeters. I had originally thought that AC amp & volt monitoring (and especially of each leg) was overkill, but I've absolutely changed my mind on that one. It's now a gotta do.
Thanks for the reply!
I wanted to add that the AC volt and ammeters for each leg was a "must" for me. I check them several times a day if I am doing any power supply switching, or have any doubt about the quality of power. I opted for the analog gauges, since they give me a better "picture" of what is happening. I have the ability to check voltage and frequency with a digital gauge if necessary.
I have my 10KW generator wired for 240 because of our dryer. With a generator that size, you need to be very careful to keep the loads reasonably balanced on each leg. When we are on the generator, I use the ammeters often to select the air conditioners to keep things balanced. I have each of the three ACs labeled as to whether they are on the red or black leg. The meters are labeled accordingly. This is especially important when we are running the dryer.
Selecting a location to pick up the current for each leg is a compromise. I located mine after the load center. That measures all of the current used by the coach. However, it does not pick up the current for the generator fans (one large and one small squirrel cage blower - remote radiator). I measured the current to run these two fans (11 amps!) and factor that into the proper leg.
When I started out, I made a list of what I wanted to be able to monitor on both the AC and DC systems. While my current gauge systems (AC volt/amp and TriMetric) do not quite meet that list, they do everything I need. It would be nice to have some alarms to warn me if things got out of range, but I am pretty careful to watch the systems.
One last thought, I check the post at each park before I plug in. I have a dedicated 50 amp plug with outlets for each leg and plug in my "Good Governor" (http://www.campingworld.com/browse/skus/index.cfm?skunum=16036) into each outlet before I plug in. Using the 30 amp adapter, my dedicated plug works for that supply as well. Also, be sure your breaker is off until after you plug in. There are folks who have had serious problems with the male plug making non-uniform contact during the plugging in process. Both of these thoughts were covered in other threads on this BB.
Jim
Quote from: rv_safetyman on December 18, 2007, 06:45:53 AM
One last thought, I check the post at each park before I plug in.
Yeah, but then it changes! ???
If you want to see a recent challenge I had,
http://www.busnut.com/bbs/messages/11/19611.html?1197987866 (http://www.busnut.com/bbs/messages/11/19611.html?1197987866)