120V/240V AC Output Quality Of Welders

I have a Miller Bobcat. The scope says the output is as pure a sinewave as I see from the utility company. That's to be expected since it is an alternator, what else could it be? The frequency varies around a bit (function of engine RPM), but only things like electric clocks and old phonograph turntables care much about the frequency being precisely

Computers all use switching power supplies, so they don't much care if the power is clean, exactly on frequency, or well regulated (within reason). They convert the AC directly to DC, chop it at a high frequency, step it down, and rectify and regulate it again at the 5 and 12 volts the computer's electronics actually need. Sinewave, square wave, or even DC is acceptable as input power as long as the voltage is relatively close to nominal (+/- 20% or so).

CRT monitors can be a different story. Some aren't regulated very well, so line voltage variations can cause the picture to expand or collapse, or go out of convergence. You may also get traveling hum bars if the frequency is off. The amount of regulation they have isn't always a function of price either. I've seen some expensive monitors show these problems, and some cheap ones which didn't. It is just a matter of how the designer of the particular model felt about good power supply design. In general, LCD monitors don't suffer these problems, and are much less power hogs too.

Laser printers generally use switching power supplies, so the comments above about computers apply to them too. They do require a lot of power compared to a computer or monitor, so there could be problems with a marginal generator.

Ink jet printers usually use a wall wart power supply, which while it is a switcher too, is generally not a very classy switcher, and may not produce good results if the frequency or voltage is too far off nominal (I haven't had any problems with my Canon and HP ink jets running on the Bobcat, though).

The same sorts of comments apply to radios and TVs too. Tape players may wow a bit with changes in line frequency. CD players generally don't care.

I use my Bobcat as backup power for the house. It runs all my computers, TVs, TiVos, satellite receivers, ham radio gear, etc, as well as some lights, refrigerator, freezer, furnace blower, and central air conditioning. The voltage dips a little when one of the bigger loads switches on, but not enough to cause any problems.

If several of the bigger loads switched on at once there might be a problem, but that hasn't happened to my knowledge while I've been running on the generator. For sure none of the computers has ever rebooted, nor has one of the TiVos lost a program it was recording, while I was running on the generator. I do try to practice power management, and don't try to run everything at the same time.

I was a little concerned that the central air might be asking too much from the generator since its starting surge is right at the full rated output of the generator, but it has handled it without complaint. I suspect Miller's ratings are a bit on the conservative side. It sure is nice to be able to sit in air conditioned comfort watching TV while all the neighbors swelter in the dark.

Gary