I was measuring the internal resistance of a D'arsovnal meter. When I connected my PS, the meter started oscillating, I quickly disconnected my PS and checked it, it seemed fine. I reconnected the PS, and just let it oscillate until it stopped. So I made a video 28V, 400k ohm series resistor and the meter, The spec's, 55 ohms internal resistance and 124uA FS. No big deal, just never saw a meter swing so much. Yes, I went high series resistance to maximize the oscillation. No, I don't have a parallel resistor to dampen it.
I can't tell if you are being sarcastic or factious or serious. But the meter is fine, it is driven by a thermocouple, it has two 22 ohm resistors in series with it. See Thermocouple and Multiply Q By meter here.
Mikek
To add to my fun, I thought I could replace the meter with a 55 ohm resistor and measure the voltage across the resistor with a Digital voltmeter. But when I did that, the digital voltmeter didn't change reading like the analog meter, if I dropped the drive by 1/2, the digital meter just stayed at the old reading, or might very slowly drift down, strange to me.
On a sunny day (Sun, 11 Aug 2019 16:00:30 -0500) it happened amdx wrote in :
You mention a 124 uA moving coil meter as far as I can tell.
I had and have meters like that; 100 uA full scale, bigger than yours and those do not wiggle, I used one for years as a kid as my multimeter with series resistors. Maybe if yours is normally shunted by a thermocouple they thought it would not be needed to add a damping system. You do so many strange experiments, from Q of crystal receivers (look up super-heterodyne to get a break) that your posting is to me just an other shot into deep space difficult to see the context. If I had a meter like that it would go into the garbage right away, not even decent scale, to much junk already. You can, with just a few opamps and some wire make your own very nice accurate thermocouple meters write some software, log it, use it to control things etc:
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For most multi meters you can buy a thermocouple probe too, and those do not wiggle either.
Meters like that were typically damped with a vane, giving a little air resistance. Maybe the vane has fallen off. Like that they're only useful for slow moving values.
On a sunny day (Mon, 12 Aug 2019 04:05:05 -0700 (PDT)) it happened snipped-for-privacy@gmail.com wrote in :
Yes, and if it is directly connected to a low impedance thermocouple then it will be damped by that (behave like a shorted DC magnet motor). So that saves them the cost of a vane, ??
I'll make you a deal, you start producing readable/useable schematics then I will look into super-heterodyne receivers. Or we can just do what we want to do and enjoy or not, each others posts. :-)
Th meter is fine works exactly a it should. In circuit it is very slow to respond, because of the thermocouple, when you make a current adjustment you have to wait for the meter to catch up. The scale is marked as it should be for it's purpose, I assume the thermocouple is non-linear and the meter is scaled to reflect that. As to throwing it in the garbage, no, I just reinstalled it into the instrument. Works great.
The new series of Q meters did away with the thermocouple and couple through a 2pf cap to a FET high input impedance amp. They also started use something called a transistor, no more tubes!
Most of it, hope we can keep our part of it that way. Mikek
It's back together now, so the only thing I can add is, when I paralleled the 55 ohm meter with a 55 ohm resistor the meter did not drop by half. It read higher than that. I can't find the info, but I think a thermocouple has a very low output impedance, much less than an ohm? The series circuit is thermocouple, 40 ohm resistor, 55 ohm meter. So that is the dampening, About 40 ohms.
Mikek
See circuit here, R204 and R204 are each 20 ohms, hand picked per unit.
On a sunny day (Mon, 12 Aug 2019 11:24:40 -0500) it happened amdx wrote in :
I do not make deals, but I have a small DVB-T antenna and a bought new DVB-T2 tuner as the system here moved to DVB-T2:
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gets several channels in HD
General Complete name : tv_noord_ffmpeg_vcodec_copy.mp4 Format : MPEG-4 Format profile : Base Media Codec ID : isom File size : 86.6 MiB Duration : 3mn 19s Overall bit rate : 3 638 Kbps Writing application : Lavf57.56.101
Video ID : 1 Format : hev1 Codec ID : hev1 Duration : 3mn 19s Bit rate mode : Variable Bit rate : 3 502 Kbps Width : 1 920 pixels Height : 1 080 pixels Display aspect ratio : 16/9 Frame rate mode : Constant Frame rate : 50.000 fps Bits/(Pixel*Frame) : 0.034 Stream size : 83.3 MiB (96%)
Audio ID : 2 Format : AAC Format/Info : Advanced Audio Codec Format version : Version 4 Format profile : LC Format settings, SBR : No Codec ID : 40 Duration : 3mn 19s Bit rate mode : Constant Bit rate : 129 Kbps Channel(s) : 2 channels Channel positions : L R Sampling rate : 48.0 KHz Resolution : 16 bits Stream size : 3.08 MiB (4%) Language : Dutch
Not bad for 23$90 free shipping Strongly recommended, can set timers too, works on mains and also on 5V.
So what can you receive on your 'bog' antenna and how much space does that take and what does it cost including the receiver? This is 2019
Satellite dishes are even better. Sat boxes are just as cheap.
It's certainly enough for anyone to find the "answer" with Google. It doesn't even require the construction of a super-computer. How about "42", is that better?
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Jeeze, talk about lazy!
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Rick C.
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