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The only major issue with this recorder is it is just such a doddle to set up and use (all one has to do is push 'record', much like a VCR). In fact, they are so simple they can make almost anyone a PQ engineer overnight. Sadly, because of this simplicity, they also attract those looking for a 'quick buck' and do nothing to credit power quality engineering! Now you understand why I say the simplicity is a problem! What is definitely in RPM's favour (in my books) is the transient waveform capture. This is the only instrument I have seen that does not overstate the problem. Others I have worked with miscalculate the transient peak, simply because they don't remove the transient from the basic waveform. RPM's hardware separates the two and the difference is startling! I have tested the transient capture against a stock-standard storage oscilloscope and the waveform is spot on! Transient peak voltages are also relatively accurate (mine is within 5%), and resolution is at 0.5µs. Anything above this (i.e. 2MHz) is RF! Actually, as a radio 'ham', I transmit at 1.8MHz, so 2MHz is well into the RF region! Now here is one thing I do find strange (in a nice way). RPM are the only people who appear to do Ground Current as well as the usual four. I know this is to do with 8 being a neat binary figure, but ground current (a fifth current channel) is just as important as Neutral (if it doesn't come back on the Neutral, it has got to come back through the Ground). The only real features missing off the RPM range is the shortfall of their Report Writer to include reports, called for by the less knowledgeable in the industry, based on some EN specifications (but then again, what is in a spec!). Admittedly I am not a fan of automatic report generators but I have heard from one guy who loves them as, no matter what mood he is in, he always presents a uniform report. As for the serious engineer, they shun these things anyway. It is a little scared of running above 707VACrms, even if that is phase-phase (making that only 410VACrms phase-neutral), but having a rock-solid 2Mohm input impedance means my usual "in-line resistive input range extender" does the trick nicely. I successfully run the unit at 760V Line-Line (690V + 10%). Talking of tricks, I also like the fact the 4th voltage channel (usually dedicated to N-E) is "fully detached" from the main phase channels, yet has all the harmonic trends etc. This allows it to be used as a 4th voltage channel in its own right (both voltage and current). Very handy in places where there is a 'control voltage' that needs to be monitored together with a normal 3-phase input. It does lack 'current trigger', although RPM do recognize that their recorders would be more useful as a tool if they could trigger when either the voltage affects the current, or the current affects the voltage - hopefully they don't take too long about getting it to us (except I have already come up with a trick for that too!). However, their claim to fame is that the PR is a "voltage disturbance analyser", and it does this job well (remember, it is a tool for measuring the quality of supplied power, not a tool to see how you're using it!). Built into a hefty, rugged aluminium casing, it is far more suited to power quality work than some of the other fragile looking instruments that appear ill-suited for use in industrial environments. One thing that has become evident is this rugged casing has inadvertently caused failures - it's even been dubbed the 'Un-Reliable Power Meter'! This is totally unjustified as it has actually come to light that the users are to blame! The rugged casing has given many the opinion that the unit can take life's larger knocks, like being dropped! Well, maybe the advertising shows a truck driving over a unit, but fitted with a hard drive means it needs to be treated with the same respect one treats a laptop! I run mine flat making it relatively impossible to give the hard-drive a serious nudge. My one has gone in to some really rough locations, and is still working a treat - even though I carry it around in a rucksack! It is decidedly not a PQ-DSO, that I leave up to the 43B. This is a "put me in and forget about me while I am recording everything for you" recorder (a character trait I am extremely fond of), and it's packed into a box a little chunkier, albeit heavier, than my laptop. And.... ... I have yet to see someone beat this!
© 08.02.03 |
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