Low-distortion Audio-range Oscillator - Page 137 - diyAudio
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Old 30th December 2012, 01:28 AM   #1361
RNMarsh is offline RNMarsh  United States
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Eagle seems like it ought to be the greatest thing ever... but my vote on it is also
I'll take a look at DipTrace. -Thx RNM

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Old 30th December 2012, 01:30 AM   #1362
davada is offline davada  Canada
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Originally Posted by scott wurcer View Post
Why does it have to be thermal RMS why not log computing? I forgot to mention that that was what I made, I epoxied a power resistor to the 3300ppm Tellabs resistor and put it in a styrofoam isolation surround. When it finally locked in I got -130dB or so.
Well it doesn't have to be thermal RMS. We have to work with what's out there and RMS stuff is available. I haven't found a manufacture that's interested in catering to low distortion oscillators otherwise we might have perfect device. Maybe not. If it's not used by industry or by the military then no one is interested, understandably.

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Old 30th December 2012, 01:36 AM   #1363
davada is offline davada  Canada
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Thank's

As for RMS in this application neither the BW or dynamic range is an issue so something like an AD637 should work just fine. I found a huge stash in my junk bin (nice gold DIP's) if you want a couple.
Sure. What do you want for them?
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Old 30th December 2012, 01:50 AM   #1364
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Sure. What do you want for them?
Nothing, just PM an address and later tell us if it is useful.
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Old 30th December 2012, 01:59 AM   #1365
davada is offline davada  Canada
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Default PCBs

This is the place I was referring to.

I see there setup charge has gone up.
Used to be $12.00.

This is a quote on 1 6x9" board double sided.
If the solder mask was left off it would be $24.00 cheaper.
I wonder then if it would be tinned?
For a development board it would be better to not have a mask.

Anyone heard of these guys?
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Old 30th December 2012, 02:20 AM   #1366
davada is offline davada  Canada
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"Thermocouples won't work since they generate DC from the heat instead of a resistance change."

A change in current is all we need. Maybe a resistor in series. Driving a virtual ground node???

Actually I got he idea for this multiplier from an old HP wide band RMS detector which used a pair of thermocouples in a vacuum tube. The one thermocouple is heated by the other converting an AC loop to DC loop.

I'll look up the model number.
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Old 30th December 2012, 02:23 AM   #1367
davada is offline davada  Canada
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I found these at Digikey.

I wonder if they are the same as the Amperite resistors?
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Old 30th December 2012, 02:56 AM   #1368
1audio is offline 1audio  United States
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They look interesting but they are polarized and need .6V to turn on so they are most likely a semiconductor circuit. And no glow. .

The Ballast resistors date back to the early 20's.

The HP3400 and HP3403 use dual thermocouples to measure AC voltage. You need a chopper amp to measure the voltage off of the thermocouple. Seeing the price for a basic vacuum thermocouple I would leave them to the standards guys. I have an assortment but it took years to gather them. Except for NIST and a few obscure devices everyone has moved to digitizing for precision AC measurement so the market for these has really shrunk.
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Old 30th December 2012, 03:00 AM   #1369
davada is offline davada  Canada
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They look interesting but they are polarized and need .6V to turn on so they are most likely a semiconductor circuit. And no glow. .

The Ballast resistors date back to the early 20's.

The HP3400 and HP3403 use dual thermocouples to measure AC voltage. You need a chopper amp to measure the voltage off of the thermocouple. Seeing the price for a basic vacuum thermocouple I would leave them to the standards guys. I have an assortment but it took years to gather them. Except for NIST and a few obscure devices everyone has moved to digitizing for precision AC measurement so the market for these has really shrunk.

I can't find any of these ballast. The company was bought out and only make relays now.
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Old 30th December 2012, 06:30 AM   #1370
1audio is offline 1audio  United States
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Amperite - Solving your relay requirements since 1922
They seem to be still at it. You may need to call them. The linear current range seem large so they could be well suited to this task.
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