From: Chuck Guzis <cclist at sydex.com> On 12/23/2012 05:29 PM, Chris Tofu wrote: So you have a 6300 or M24 that you've used the Eagle 5151 clone with? I'm surprised that it worked. The 6300 outputs a 640x400 display, so the frequencies are actually closer to VGA than monochrome.? (about 30KHz horizontal/60Hz vertical, if memory serves).? IBM hi-res CGA mode was emulated by doubling each horizontal line. C: a VGA horizontal scan rate is 31.5 khz. Off the top of my head I don't know what a 5151s is, about 22-23 khz allowing for overscan. A Tandy 2000 or AT & T 6300s is about 25 khz. A vga has 480 lines of resolution (although there is that 400 line mode, which could possibly mean vga monitors are dual frequency. Anyone?). 400 is closer to 348 then 480. I've used a 6300 with an Acer AL1916W display with very nice results. It's not monochrome, but it's very sharp. C: I'm sure you're relating your success w/that monitor accurately, but is it a multiscanner? I can't even understand how a ttl video signal is compatible w/a monitor that expects 1 volt peak to peak rms. You can, using jumpers (and removing a PAL on some versions) disable the inboard video and add an EGA or VGA card.? I'm not aware that the BIOS has any support for a standard MDA card.? The 6300 is odd in that the video card also serves to couple the motherboard to the bus converter board, so it can't simply be removed. I think it'd probably toast a 5151 display. ?C: I'm at a loss to understand why you think that. And no I've never plugged anything foreign into a 6300, but a ttl monitor seems the natural choice.

? "1 volt peak to peak rms"?? Well, which is it? ;) ? ? ? ? ? ? -Dave ?C: I was of the persuasion that the "1 volt" was an rms measurement. In reality the signal varied between +/- .707. I'm googling...

? "1 volt peak to peak rms"?? Well, which is it? ;) On Wed, 26 Dec 2012, Chris Tofu wrote: Think of it as a type of AVERAGE. You get a certain height peak, but are more interested in the average voltage. Sometimes the range is most useful, sometimes the average. BUT, these are AC signals, and some are positive, and some are negative. If you were to take an "ARITHMETIC MEAN", and just add up the voltages and divide by the number of samples, you would get ZERO. (assuming no DC component offset) You COULD take the absolute values and average those. BUT, spikes, or odd shaped curves can give you a useless average. Likewise averaging "BillG" and "Billy in the box under the bridge", which is why most people talk about MEDIAN home price, NOT MEAN. OR, you could SQUARE each number, average [MEAN} those squares, and then take the square root. Hence, ROOT of the MEAN of the SQUARES, or RMS. (Square root of square is one way of getting absolute value). THAT gives a type of average that is more useful in terms of how much work you can get out of it, etc. (cf. "Variance", "standard deviation")

On 12/26/2012 08:38 PM, Chris Tofu wrote: Yes. In fact, the most accurate RMS to DC converters (as components in RMS voltmeters) are "thermal converters", which convert the input energy to heat, then measure how much DC energy is required to heat another heating element to the same temperature. Measuring the area under a complex RF waveform in real time is tough to do. I have an HP 434A Calorimetric Power Meter, introduced in 1958. It uses a recirculating oil system (it's as much plumbing as electronics) to do just that. See a photo and block diagram about midway down this page: http://www.hpmemory.org/wa_pages/wall_a_page_10.htm Later the same basic setup was implemented by Linear Technology in a DIP package, as the LT1088. Some metrology-grade "true RMS" volmeters, like the Fluke 8506A, use a heating element and a thermocouple in a sealed, evacuated glass bulb. Voltages? Not terribly often, but sometimes. dB, however, is a relative measurement...it is not possible to directly represent a voltage in dB. To do so, you could say "dBV", which would be "decibels relative to one volt". It is common (like about 100% common) in electronics to represent RF power in dBm, decibels in relation to one milliwatt". For example, a common doubly-balanced mixer has an input drive level of +7dBm, which is 7dB higher than one milliwatt, or roughly 5mW. 20dBm, or 20dB over 1mW, is 100mW. dB for ratios, like gain or attenuation figures, and dBm for absolute power, is a lot more convenient to work with than (say) mW. -Dave -- Dave McGuire, AK4HZ New Kensington, PA

ok batting a thousand today. Meters display ac voltages as rms. Peak to peak rms doesn't make a whole lot of sense I guess. Apologies.

On 12/24/2012 01:06 PM, Dave McGuire wrote: And a lot of multimeters do a darned poor job of measuring RMS for anything other than a continuously recurring sinusoidal waveform. You could have the statistical RMS error of a cluster of P-P readings performed by a monkey, I suppose. :) --Chuck

On 12/24/2012 02:49 PM, Dave McGuire wrote: It's much worse than that--just go to YouTube and search for "Free Energy" or "Magnet Motor" for tons of examples of how a cheap DMM can be misused. "Hey, I'm getting 150% efficiency out of this because my DMM says so." Not quite as bad as those (and they're there) who use voltage as a measure of power. It makes the head hurt. --Chuck

I don't think so. Hows this for a lovely bit of stage magic... https://www.youtube.com/watch?v=e9xwtTNRak8 Dave Wade G4UGM Illegitimi Non Carborundum

On 2012 Dec 24, at 4:47 PM, Chuck Guzis wrote: A local newspaper here ran an article a few years ago about a basement-tinkerer who had invented a 'free energy' source. He had a box filled with wires and electrical doo-hickeys and claimed that more energy came out than went in, based on calculations and measurements from meters hanging off the thing (he must know what he's talking about). It had been examined by "experts" and nobody could explain to him what was going on or show him that he was wrong. Of course, the experts were flummoxed, as opposed to him being incapable or deaf to understanding. Of course, he wouldn't let anyone examine the internals as they could steal his design. And of course, all the big boys (the power companies and so on) were marginalising him because it would put them out of business. I think he was sincere in his belief, but I'm guessing he didn't understand the concept of 'power factor'. The better question is why did the newspaper devote space to it.

Actually, the peak value equals the RMS value for certain waveforms. It's even possible for the peak-to-peak value to equal the RMS value, but - I think! - not for waveforms that cross through zero. /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTML mouse at rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B

On Mon, 24 Dec 2012, Chris Tofu wrote: Not to worry! although it WAS funny!