|Voltage Range/resolution:||0-60V, 0.01V|
|Current Range/resolution:||0-100 A, 0.1A (supplied shunt)|
|Current Range/resolution:||0-20 A, 0.01A (20A shunt)|
|Tachometer Range:||to 64,000 RPM, one to seven blades|
|Power:||Internal 4 cell NiMH battery|
|Dimensions:||4.0 x 2.0 x 0.7 inches (10.2 x 5.1 x 1.7 cm)|
|Weight:||2.3 ounces (65g) for meter, 0.9 ounces (26g) for shunt|
|Price:||$89.95 US. Optional 20A shunt $13.95|
|Available From:||AlleRC in the US|
|Available From:||various distributors worldwide|
A relative newcomer to our electric flight world is a multi-national company called Hyperion. Their product line includes high quality motors, speed controls, gearboxes, and lots of small bits that are vital for e-flying such as prop adapters and prop centering rings. They also have a line of almost-ready-to-fly airplanes that are getting a good deal of attention lately.
But Hyperion have also created a unique multi-purpose instrument/tool called the Emeter. This device combines the functions of a tachometer (for 1 to 7 blades) and a multi-function test meter such as the Astro Flight Whattmeter or RC Electronics Watt’s Up. All of this data can be captured and stored for later readout – in fact five sets of these data can be stored at any one time – all by pushing two buttons. It was this feature that really got me excited about the Emeter when I first heard about it. I looked forward to no longer trying to remember the tach and multifunction meter readings long enough to write them down – or rerunning a test case because I couldn’t. Because it records current, voltage and RPM, by adding propeller constants for the prop you are using it has all the data needed to compute power system efficiencies at any throttle setting (more on this later).
But wait, there’s more. If you’d rather capture data over a longer period of time with a computer, the Emeter has a data logging ability via a serial connection with a Windows-based computer. You can also use that same serial connection to update the Emeter’s firmware when updates are made available (and they have added several features since I got mine). More on this in Part II.
The Emeter can also be used to very easily program the various options of the Hyperion Titan brushless motor controllers via a simple interface cable (that costs only $3). I discussed this capability a little bit at the end of the the November 2005 edition of A Controlling Interest. It can even be used as a servo tester/exerciser. And it’s very compact and lightweight, with a very simple four-button user interface for all this capability.
The Emeter was designed by Mark and Phil Connolly in Australia and is manufactured by Hyperion in Taiwan. The computer interface and logging software is provided by Rod Badcock in the UK. Distribution comes via Empire Hobby in the US, Aircraft World in Japan (an Ezone sponsor and the source of my unit), and others around the world - so this is truly an international product.
According to Phil, the primary design goals were to create a tool that would be useful at the field (instead of at home, tied to a computer) so small size, generous information on the display, an internal battery and that unique ability to store data points for later analysis were the key features. It was only after there were prototypes in the field in 2004 that the Connollys got connected with Hyperion. Hyperion was very much interested in producing the product as part of their entrée into the RC market.
The prototypes already had a serial interface for use in updating the on-board firmware and for dumping data out to a computer, so an interface for programming the new Titan line of ESCs from Hyperion was an easy addition.
Since the initial Emeter release, this capability to update the firmware has made it easy to add new functions. The servo tester/exerciser feature, and the ability to display and store minimum and maximum voltages and maximum amperage in a session were both added to my Emeter via that interface. And more is to come, I am sure.
Some of what this meter can do...
My first impression after opening the box was “gee, that’s smaller than I thought it was”. The Emeter itself is about 2 inches wide, 4 inches long and a bit over 5/8 of an inch thick. On the face of the unit are a six-line LCD display and four buttons – marked “A”, “B”, “C”, and “D”. These four buttons (and the power switch) comprise the user interface to the Emeter.
The case itself, while plastic, feels substantial in in my hands, and the buttons and power switch have a quality feel in operation. The connection to the shunt is positive and solid. Inside is a neat and clean layout on a single board with no extraneous jumpers. The overall inpression is of something built to be used for a long time.
However, the ribbon cable between the board and the display, which you can see in the picture below, is quite thin and requires careful handling. There's really no reason to open the Emeter up, anyway. I just did it so you could get a sense of what it looks like in there.
When the Emeter is turned on (after the initial startup message) the bottom line of the display lists the current functions of the four buttons. What these functions are varies depending on which mode the meter is in, though generally button “A” is labeled “mode” and is used to cycle through tach to motor to battery to peaks to memory mode on successive pushes. More on the other buttons and what they do when in the “Using It” section below.
Recessed in the left side is a slot with a four-pin connector. This is where the computer interface cable or the ESC-programming cable is connected. This is also where a modified servo Y-harness is connected when you use servo-exercising function. I’ll cover the things you can do with this connection to the Emeter in Part II, since there’s plenty for another whole article there.
In the right side is an on/off switch, for the Emeter is self-powered from an internal NiMh battery. Centered on top is the opening to the optical sensor for the tachometer function. On the bottom is a round connector with four pins. This is where the lead that runs between the current shunt and Emeter is connected.
One of the ways in which the Emeter is different from other multi-function meters is that the actual path through which the power system’s full current must pass is quite short – a two-inch long shunt carries the current and the reading is communicated to the meter through a flexible 10-inch lead. This also lets you put the actual shunt in the power circuit and still get the Emeter unit itself in a position to be used as a tachometer at the same time.
Further, this short shunt doesn't add much length to the battery side of the circuit and is less likely to cause problems for your ESC. Depending on how close you're operating to the particular ESC's limits, adding several inches to the current path, as you do with inline meters, can lead to voltage spikes that are too much for the ESC's input capcitors.
There are two shunts available. The standard one supplied with the Emeter is for reading currents up to 100A, with a maximum resolution of 0.1A. The optional one is for up to 20A, with resolution up to 0.01A. (The upper voltage limit in either case is 60V.) Both shunts end in molded-in Deans Ultra connectors.
One end of the shunt is marked “Battery” (and has the male Deans Ultra) and the other is marked “Load” (and has the female connector). You are expected to hook the drive battery up to the “Battery” side of the shunt regardless of whether you are running a motor or charging a battery. More on that below.
Of course if your power system doesn’t happen to use Deans Ultras then you need to make up adapters for what you do use. I made up two sets – one going to Anderson Powerpoles and one going to mini Deans connectors, since they are what I use. Even with the adapters I've made up the current path through the Emeter's shunt and the adapters is shorter than through my other multi-function power meters.
Another way the Emeter is different from other multifunction test meters is that an on-board four-cell rechargeable NiMH battery powers it. When fully charged this little internal battery will run the meter for several hours of testing.
Connecting a battery (or other power source) with a voltage of 7V or more to the battery side of a shunt (6 or more nickel cells or two or more lithium cells) while the shunt is connected to the Emeter AND the Emeter is switched off charges the internal battery. This can drain the external battery down if it’s left on for too long. I overdrew a 3s lithium battery by leaving it on to charge the Emeter and then forgetting about it for a couple of days, so be careful. I now most often use my old Ace Metered VariCharger instead of a battery to charge it – no danger of running the battery too low that way. Since the battery is NiMH, if the Emeter hasn’t been used or charged for awhile (say a couple of weeks or more) it is a good idea to recharge it.
It will warn you in the display if the battery is getting low, and the data stored in its memories (see below) are retained even if the battery runs down. Beginning with firmware version 1.21 if the battery runs out while the Emeter is in use it will store the last good data in memory number 5, where it can be retrieved after the internal battery is at least partially recharged.
The Emeter can be used as a standalone tachometer for props and fans. Two blade tachometer (“Tacho” down the right side of the display) mode is the default when you first turn it on – and no shunt need be connected to use it this way. (If one is not connected, the unit will report that the 20A one is connected upon power-up.) To do so, just turn it on and use it as you would any optical tach – point the sensor at the spinning prop and wait a moment for the reading to stabilize. Readings are to the nearest 15 RPM below 9000 RPM and to the nearest 30 RPM above that.
If two blades isn't the correct number for your application, simply push button “C” (labeled “Blds” on the bottom line of the display) to sequence through any value from one blade to seven. The higher numbers of blades are for use with ducted fan impellers. I am told that in tests fan speeds up to 47,000 RPM have been reported. The theoretical upper limit the unit can read is 64,000 RPM.
If you want to simply hold the displayed reading, push button “D” (labeled “Hold” on the display). When the reading is being held, the label for this button changes to “Cont” for “continue”, and the label for button “C” changes to “Save”. Pressing Save will bring up the list of the five memories, with the first unused one highlighted. Pressing Save again at this point stores the reading in that memory slot. You get a brief message “Saved in Mem-x” (where “x” is the memory number selected) and then the tachometer display returns.
Memories in use have an asterisk after their labels (such as “Memory-1*”). You can select any memory by pressing button “D”, now labeled “Next”. Pressing “Save” (button “C”) stores the held reading in the selected memory, overwriting what’s there if you select one that is already in use. Alternatively you can press button “A” (labeled “Esc” for Escape), which will take you back to the tachometer screen without storing anything.
Readings can be retrieved later by going to the Emeter’s memory mode, as described below.
One unique feature of the Emeter is its ability to calculate an estimate of the output power to the prop, based on the RPM and prop characteristics then display this along with the RPM itself. This estimate is similar in concept to that calculated by several of the software motor performance estimation tools such as MotoCalc and ElectriCalc.
To use this function you have to tell the Emeter the characteristics of the particular propeller you are using. While the Emeter is in “Tacho” mode, button “B” is labeled “Cfg” for configuration. Pressing this takes you to the screen where prop constants are entered. There are two numbers involved. One is a “power factor”, which by default is 3.00 – as theoretically the power absorbed by a prop goes up by the cube of the RPM (doubling the RPM into a prop takes an eight-fold increase in power to the prop.) The second number, labeled simply the “prop constant”, is the number that yields Watts when multiplied by RPM (in thousands) is raised to the Power Factor. (W= const*(RPM/1000) ^PF).
An extensive list of prop constants, based on dynamometer testing done by the likes of Wilhelm Geck and Phil Connolly himself, are available here. Also, there is very informative writeup on propellers, selection, constants, how they are derived, and much more called “Hyperion Prop Talk” here.
For example the values on the page linked to above for the APC 10x7 slowflyer prop are a “prop constant” of 0.337 and a “power factor” of 3.30. These would be the values you would enter into the tach configuration screen on the Emeter in order to get power and efficiency readings out when testing a power system that was running that prop. Based on Mr. Connolly’s testing, the power in Watts absorbed by the APC 10x7SF can be calculated as 0.337*(RPM/1000)^3.30.
To enter the prop constants, push button “B” from the tachometer screen to get to the tach configuration screen. From here you first enter the “PropCons”. Pushing button “B” (labeled “Inc” for increment) raises the highlighted digit by one. Pushing button “C” (labeled “Dec” for decrement) lowers the highlighted digit by one. Increment and decrement both loop around from 9 to 0 or 0 to 9, so you can take the shortest distance to get there (this feature was added with firmware release 1.20 – thanks, Phil!).
Change the first digit if needed, then press button “D” (labeled “Next”) to go on to the next digit. Change or skip each of the five digits in the prop constant as required. Pressing “Next” again takes you to the first digit of the Power Factor, which by default is “3.00”. Change that if needed (you will seldom need to do so) then go on to the two digits after the decimal point. Once all the entries are made, press button “A” (labeled “Save”) to return to the tachometer screen. This set of constants is then stored until you change them.
Whenever a value other than 0.0000 is entered for the prop constant, then in addition to the RPM reading you will get a power reading, in both Watts and brake horsepower (BHP) on the fifth line of the tach display (just above the button labels). These values are saved in memory along with the RPM when a tach reading is stored as described above.
I find using the tachometer function much easier to do than it was to describe it here. My only point of comparison from a purely digital tachometer-use standpoint is my 20+ year old NorCal Avionics AccuTach. Like that older digital tach, it helps to give the reading a few seconds to settle. That’s a fair trade off, most of the time, for the resolution.
I have noticed that compared to my old AccuTach the Emeter’s tachometer is fussier about lighting conditions and is much more sensitive to reading AC-powered artificial lighting. In particular, any fluorescent lighting in the room is read by the Emeter (so you get a reading of 3000 RPM in two-blade mode if you have 50Hz electricity or 3600 if you have 60Hz electricity). It will even read strong incandescent light that way. The workaround is to shine a battery-powered flashlight on or through the prop, or use natural light coming in a window. I have found that shining the light on same side of the prop as I’m reading works OK and keeps me from having to reach around a spinning prop.
Of course at the flying field, where the Emeter was designed to be used, this is not a problem. Because the combination of the tachometer and multi-function meter and memories is so strong, messing with a flashlight on my test stand is worth it to me. I have recently rigged up something on my test stand from a battery-powered LED book light to make this a little simpler than holding the Emeter in one hand (and pushing hold, save, save when I want to) while holding the flashlight in the other.
The Emeter can do the tasks of the various multi-function electric power system meters like the RC Electronics Watt’s Up and Astro Flight Whatt meters – display volts, amps, watts, ampere-hours, minimum volts, maximum amps, and so forth. It can also display the time of charge/discharge like a number of battery chargers and cyclers do. With the shunt inline in your power system between the drive battery and the speed control and the sense lead plugged into the base of the Emeter, all the usual multifunction meter data are available.
The Emeter has two different display modes for this sort of information. One is more for looking at motor performance and is called, not surprisingly, Motor mode. To get to Motor mode, press the mode button (button “A”) once from the tachometer screen.
This one displays Volts, Amps, and input Watts (as you’d get from most any wattmeter-type unit). It also displays RPM from the tach sensor. As mentioned in the “tachometer” section above, given prop constants, the Emeter can calculate output Watts. Since, in this mode, the meter is already measuring input Watts, it can also calculate and display the overall power system efficiency! It will do so whenever both a non-zero prop constant is entered as described above AND the necessary calculations with prop watts and input watts yield a number less than 100%. (If you're running a prop that loads the motor less than the one for which the constants are stored, numbers over 100% could otherwise be calculated.) Note that this efficiency is not only motor efficiency, but rather the aggregate of the motor, the ESC, the wiring and connectors, and gearing (if any).
Something I found very interesting is reading the efficiencies of a particular motor at various throttle settings other than full. With the five memories, it is possible to store several different sets of values quickly for later study. Note that before holding and storing a set of readings you should let the RPM settle each time you change motor speeds/throttle settings. The calculated efficiency lags the RPM change a bit and depending on whether you’re throttling up or down it may read low or high until the RPM reading stabilizes at the new setting.
While in Motor mode three of the four buttons are active. Button “A” switches modes, button “B” (labeled “Cfg”) takes you to the propeller constant entry screen as described above, and button “D” is the hold button. When a reading is being held, as with the tachometer function, button “D” becomes “Continue” and button “C” becomes “Save”. This also works as described above. All the information on the display, including RPM, power and calculated efficiency is captured and stored when you save a reading.
The other mode is more focused on battery performance so is called Battery mode – accessed by pressing the mode button one more time from Motor mode (or twice from the power-up tachometer screen). In Battery mode the momentary and peak voltage, momentary current, mAh (both in and out), and elapsed time are shown. Whether capacity in (battery being charged) or capacity out (battery being discharged) is relevant depends on what you do. Since you’re supposed to hook the battery up to the side of the shunt marked “Battery” regardless of what you’re doing, separate reading of “in” and “out” capacities are needed. Current reads as a positive value either way.
When in Battery mode the four buttons are “Mode”, “Clr” – which zeroes the readings on that screen - “Strt”, which starts the timer running, and which changes to “Stop” while the timer is running, and “Hold”. As before, pressing “Hold” freezes the readings on the screen and makes the memory function available via the “Save” button (button “C” as usual, and overriding the timer start/stop function on that same button).
One thing that took me a little getting used to is that the mAh in/mAh out displays (and the timer) didn't start counting until I actually pressed “start”. The values didn't accumulate from power-up as with other volt/amp/watt meters. This has also been updated with firmware version 1.21. From that version onwards the mAh accumulators run whenever the unit is powered on. The timer still needs to be started and stopped manually - but that way it's serving as a true timer. The timer, by the way, will continue to run if you switch to another mode.
Also, since the meter doesn’t draw any power from the battery being tested while the test is underway, you need to make sure its internal battery is fully charged if you want to do a test that will take awhile. One place I’ve run into this is capturing a full-length lithium battery charge – for example measuring capacity put into a battery while charging with a charger that does not have its own display. This is not a problem as long as the battery is fully charged when you start your charger testing. But it's a tiny NiMH battery and does self-discharge some over time.
A new feature added with a recent firmware upgrade is the ability to capture and display the minimum and maximum voltage, the maximum current and the maximum RPM for a session. This display is one more press of the Mode button past Battery mode. In this mode button “B” is labeled “Clr” and can be used to reset the values displayed.
Added at version 1.21 is the ability to estimate the internal resistance of a battery. What it actually does is take two peak measurements and use the current and the voltage differences to calculate the effective resistance of the whole setup. This is another calculated value that while it may not be a laboratory standard measurement it IS a way to compare one battery with another on your own setup. In the illustrations below the load was supplied by my CamLight PD-12V discharger, so the connection setup went Camlight discharger - Powerpole to Deans Ultra adapter - Emeter shunt - Deans Ultra to battery connector adapter - battery
One more press of the Mode button past Peaks mode brings up the first memory display (“Mem1” down the right edge of the display). Whatever was last saved in memory position 1 will be displayed here. This could be a screen from the tachometer display, motor mode, battery mode or peaks mode (except for the battery resistance calculation). Pressing button “D” (marked “Next”) takes you to memory 2, the next press takes you to memory 3, and so forth. From memory 5 you go back to memory 1.
When in Memory mode button “C” is labeled “Clr”. Pressing it clears the contents of the current memory. If the memory contains an RPM value (from Tacho or Motor mode), button “B” is marked “Cfg” and again takes you to the propeller constants page as described before. This lets you take a saved reading and get an output power and efficiency calculation after the fact.
Pressing “Mode” from any memory takes you back to the beginning – to Tachometer mode.
If you want to see what’s going on with a given power system or compare various power system parts to one another, the Emeter's combination of volt-amp-watt meter function, a tachometer and the ability to store up to five sets of data for later analysis or recording is a dream come true. Gathering all these data with a single self-powered device is a great step forward.
But that’s just where it starts. Once you have entered the prop constants for a prop you use in a test, it is easy to evaluate the efficiency of motor/ESC combinations. You can do this at full throttle and at any throttle setting and save the data as you go, as I illustrated above in the "Motor Mode" section.
I should mention again here that, just as with performance estimation computer programs, the accuracy of the efficiency numbers calculated are only as good as the prop constants they are based on and the fairly straightforward calculation used to arrive at the efficiency number displayed. But even if the constants for the prop you’re using at the time aren’t perfect or its performance isn’t perfectly modeled with a fixed constant, the results from run to run with a particular prop ARE directly comparable. So, you can really get a look at the relative efficiencies of two motors or two speed controls, or even a more complete look at how a given motor/prop/gearbox combination performs on a range of different batteries.
That said, the numbers I’ve been getting since I’ve begun using this capability of the Emeter have been quite reasonable – and VERY interesting. This is certainly one more source of data for reviews of other pieces of equipment in the future as well as day-to-day evaluation of power systems and more for my own flying fun.
As you can see, the Hyperion Emeter has an unmatched combination of capabilities for power system testing. These capabilities are available without tying you to a computer (though, as we will see in Part II, when you do, there are even more things it can do) so you can use them at home or at the field. I've had mine for over a year now and am still learning all it can do. Highly recommended.
Part II will cover the different things you can do to extend the Emeter's capabilities by connecting things to the its serial connection, including updating its own firmware, computer data logging, programming Hyperion Titan ESCS, and even testing servos. Look for that in a couple of months or so (but regular readers will know how bad I am at predicting when the next article will be finished).
Two more things: First, there is an Emeter video hosted on the Aircraft World site. Even though it's not up to date with the latest firmware versions it gives a real sense of what this tool can do. Warning: it's over 20 MB so you might want to do a right click and save it locally before playing.
Second, at least until it's posted on the Aircraft World and AlleRC sites, version 1.21 of the Emeter firmware can be had here:
If you have an Emeter and haven't done a firmware upgrade before, the procedure is about halfway down this page.Last edited by Mike Kolesnikov; Jul 20, 2006 at 02:08 AM.. Reason: correcting vendor name
|Jul 20, 2006, 05:14 AM|
Wow Bernard, very nice. I thought that this would be posted on the Ezonemag.com site, not in a thread here. I love my Emeter. Best investment in testing equipment I've every made. It sure makes "motor testing" easy. I had a slight problem with the connector for the shunt coming loose just a little bit from the case. Shoved it back in tightly and put a drop of CA around the "collar". Fixed. I use mine a lot.
|Jul 20, 2006, 03:11 PM|
The new article system at Ezonemag and allied sites uses the message system to hold articles. There is still a link from the www.ezonemag.com page and all the old articles, all the way back to the beginning are now accessible from there (see the archive menu on the left side of the page). This article is at the top of the page at the moment.
To be honest, I didn't look as that's sort of beyond my realm of knowledge anyway. I'm sure Phil Connolly could tell you. He's philmaur here. BTW, long time, no see.....
|Jul 20, 2006, 04:34 PM|
New York City, USA
Joined Oct 2003
|Jul 20, 2006, 07:13 PM|
|Jul 20, 2006, 07:38 PM|
Joined Feb 2006
Great review, sounds like a good product. The only thing I'd consider changing if I were them would be the use of deans as standard connectors. Maybe offer "plugable" connectors, then you could buy the meter with whatever type connector you wanted, or swap them out later (without having dongles floating around).
|Jul 21, 2006, 09:18 PM|
1. Longer lead to the shunt.. sometimes hard to juggle it all at the current length.
2. A shorter shunt - the length makes it hard to use in a smaller model where the gear is already installed
3. Option of a 15a or so short shunt with JST connectors and/or mini deans (I actually would want the JSTs) for small power systems..
|Jul 22, 2006, 10:32 PM|
Hi Spinnetti, I have a possible solution for your connector problems. I make up "Medusas"! The connectors we use in this hobby are seriously non-standardized!I find I need to be able to make unlike connections for charging,metering and hookup."Medusas are either two seperate connectors such as a standard Deans soldered wired up, soldered and insulated to a jst plug or what ever you need.These are typicaly for charging or allowing the use of diff. battery connectors to motors. batteries and escapements. Make sure you have thought out connectors and wire that are safe and in perfect working order and make sure you know exactly how to maintain correct polarity....failure to do so can result in a number of dangerous and destructive outcomes. The second type of "Medusas" are used typically for measuring and have at one end a connector tht mates with one of my meators and then are ganged to a few connectors that are typical for what ever I may measure. Here is an example, A Deans plug to fit the Deans on my "WATT METER" device. then a few connectors that are used to measure motor ot power paramaters, Each of these connectors are seperatly attached to the Deans so I might have a JST, a Molex type a Deans micro etc.Do not exceed your soldering and insulating abilities. One safety hint is to have these multileads differnt lengths to avoid shorting. Think this stuff through and be realisitic about your abbilities to solder and insulate
safely.[/B]Hope this helps. Lee Sherwood McDonald
|Jul 23, 2006, 06:12 AM|
I think the installed rechargeable battery is a bit awkward.
A simple clip-off back and space for some AAAs would be much more straight forward.
It comes with a 100 Amp shunt, a simple Deans plug-on resistance that reduced
it to 20 Amps (at no extra cost) would be handy.
I don't really have a problem with Deans, as they work OK and are proven, and are easy to get.
I sometimes use mine as a charge monitor for my LiPos, and it works quite well.
I think extra software and features for charge monitoring (and control ??) would be nice.
I wish I could use it to program my CC phx ESCs, but as this is a rival brand I doubt this will ever happen.
Overall a very neat and handy unit, of high engineering quality.
If you do any electric powered modeling this gadget is too useful not to have.
|Jul 23, 2006, 09:49 AM|
I hadn't thought of that, but yes, I guess the servo tester function could just as easily drive an ESC. I'll have to be sure and try that for Part II.
|Jul 24, 2006, 07:41 AM|
Probably I should wait for the part II but, is it possible to show in the same graph different readings to compare motors-props?
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