Recently, the Alpha Meter was introduced by DCC Concepts as a competitor to the RRampMeter made by DCC Specialties. The graphical comparison DCC Concepts uses to illustrate the differences between the two meters is spurious at best, and we feel the need to address this. Take a look at the table below:
The price comparison is only based on the V.II. The RRampMeter is available in four different versions which have different price points: I, II, III, & IV. The RRampMeter can be facia mounted just like theirs. DCC Specialties has several UK based distributors. Regardless, we have factory based support, so this doesn't matter if it is in the UK or not (although we speak American English).
So really, the above table is meaningless.
OK. Let's dive into the weeds and geek out here. The following is a BIG data dump.
The Alpha Meter can only be facia mounted. Any version of the RRampMeter can be used around the layout, on the track. This is what you really need for troubleshooting. A fascia mounted meter only displays the amperage and voltage measured from wherever it is connected to the system. It won't show a voltage drop located after a bad rail joiner, nor will it allow you to locate a short.
A four digit display is more accurate than a three digit display. NO! A four digit display has more resolution. Accuracy is another issue. Keep that word 'accuracy' in your head for later. DCC Concepts doesn't actually specify their accuracy (they claim it is the same as their resolution). We specify +/- 2%. Also, for low currents (where it really makes a difference) the RRampmeter displays 2 digits of resolution after the decimal point, which is mathematically equivalent to their 4 digit display. On the voltage side, rounding voltage up or down 50mV makes no difference in setting your track voltage. The last digit is just going to continuously spin while you are running trains and electricity is flowing as intended.
They claim 0.03% of full scale voltage and 0.1% of full scale current accuracy. Remember, they are saying that accuracy is the same as resolution, which is +/- 0.01 when max voltage is 29, max current is 10. This kind of accuracy is what a $500 Fluke Multimeter will do. We think they are mixing up resolution and accuracy as explained above. Further, we think what they are doing is peak detecting the voltage, then using that value for DCC and DC, or multiplying by 0.707 for the AC sine wave. For a pure square wave or a pure sine wave, this is accurate. BUT, DCC is not a pure square wave, and large scale layouts using AC are not a pure sine wave. Due to waveform distortion, the actual RMS value of DCC is generally NOT equal to the peak voltage of the square wave. If we are right about their method, then their accuracy on a real layout is not as good as our RRampMeter.
The RRampmeter takes a large number of samples [around 750] every second of the voltage/current, then calculates the RMS value (Root Mean Square - square each sample, add them together, divide by the number of samples, take the square root). This will give a correct (accurate) value of the voltage/current independent of the actual waveform. This calculation is done independent of the type of input (DCC, DC, AC). This is because, by definition, the correct value of any voltage is the statistical RMS value. As an aside, if each sample has exactly the same value, then the RMS calculation gives the value of each sample - i.e. the DC value. In addition to all of the above, the Alpha Meter is made in China while the RRampMeter is designed and built in Essex Junction, Vermont, USA.
We hope that this proves useful and informative. If you've got any questions about the RRampMeter or how to use it, please don't hesitate to email us.
Accuracy refers to how close a measurement is to the true or accepted value.
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