This unit has, thus far, exceeded expectations. It's very well built, definitely "beefy" (at 19.5 Lbs. [including power cord]), handsomely 'packaged,' and of isolated construction - all at a commendably fair price.
Initial impressions were, well, pretty amazing: The unit was cocooned inside not one, not two, but *three* double-wall-thick-cardboard cartons + foam protective blocks on the inside-most container. Needless to relate, it turned out to be not only functionally impressive, but also cosmetically perfect. I have never seen a piece of electronic equipment packaged this well.
It is electrically quiet, with very little electrical noise / ripple - and as an isolation transformer, considerably safer to operate than the (albeit cheaper) competition.
To be even approximately accurate, the unit's AC voltage dial assumes an input line voltage of 117VAC. My home's voltage is a little over 125 VAC - and remained quite stable as measured while I conducted several tests of accuracy and linearity as I advanced the dial in 10 volt increments up to the max dial reading of 130 VAC.
Running the unit with input voltages anywhere in the range of, say, 110 to 130 VAC is all fine, of course, but in an effort to gauge the approximate accuracy of the dial reading vs. actual measured voltage, I 'derated' the measured output voltage readings by a 125-to- 117 ratio to better accord with the manufacturer's nominal / expected input voltage.
I measured the OCV two ways: (1) via the little digital panel meter supplied on the face of the unit, and (2) with my trusty Fluke 87V VOM. Here is what I observed, as a percentage above or below the "dial-indicated" voltage - as measured by these two methods (again, "corrected" for the difference between the supplied [125] and manufacturer-specified [117] input voltages):
Dial Setting Panel Meter Fluke 87V
0 0.0 0.0
10 +12.3% -3.6%
20 7.6 +2.0
30 6.1 0.5
40 5.3 0.6
50 4.8 1.1
60 4.5 1.1
70 3.0 0.6
80 1.8 0.7
90 3.0 0.9
100 2.0 0.4
110 3.0 1.0
120 3.0 1.0
130 3.7 0.8
Setting the dial voltage was done as carefully as I could manage, even inscribing a thin white line on the outer rim of the dial to assisting me in lining up the pointer with the indicated voltage - but no claim to absolute perfection is intended.
The messages here are pretty clear:
1. Without derating or uprating your own situation's supply voltage to the manufacturer's 117 VAC input voltage, you will be misled if you rely only on the dial setting. Don't even think of doing that unless you miraculously find you have exactly 117 V.
2. The little digital panel meter (in my example unit) is 'off' by 6 - 12% at 30v dial readings and below (even if you do 'correct' your supply V to 117V - improving to ~ 2 - 5% accuracy error above 30V dial-indicated voltage.
3. If all you are looking for is 'reasonably close,' you can make in-your-head suitable corrections and go with those. Or, best of all:
3.After all of the discussion above, if you want accuracy, just get out your quality digital VOM, plug the probes into one of the two outlets - and set your voltage in that way.
The good news is that output behavior is all quite linear, with no visible 'jumps' or 'dips' as the dial is advanced.
Also pay attention to the manufacturer's more detailed ratings (which, truthfully, could have / should have appeared in the initial / online description) - regarding necessary reductions in output wattage (VA) loads at which the unit can be safely operated when extended operation is contemplated at higher loads.
All in all: a solid unit - great addition to the bench - very pleased.
