Actually, function generators are very useful. Their square waves are invariably better than those from general purpose bench oscillators and if you're measuring frequency response, a function generator is much better than a Wien bridge because all Wien bridges change their amplitude slightly from one end of the range to the other. I use my function generator for frequency responses and my swanky AC test set for distortion.
Hi EC8010,
True, I monitor the sine output and correct it. The input capacitance of the DUT can affect this too.
Now if those digital generators were affordable, you know, really low THD with digital level and frequency. Random wave form generations and pseudo noise wave forms. I think HP makes one.
-Chris
True, I monitor the sine output and correct it. The input capacitance of the DUT can affect this too.
Now if those digital generators were affordable, you know, really low THD with digital level and frequency. Random wave form generations and pseudo noise wave forms. I think HP makes one.
-Chris
Hi lykkedk,
You should use a buffer unless one is included in the circuit. The buffer can be an op amp circuit or other discrete type.
The lamp stabilized types have a variable distortion and level with frequency. The lamps used can be driven with an op amp, so very low current types. I do not recommend this type, but they give okay performance in a fixed frequency application. If you can find a Jfet control type the performance will be much better. To vary the frequency, you may be further ahead with an XR8038 or XR2206 types. They are much more forgiving and will work properly (for them) much more quickly.
-Chris
You need to build a PSU. The one suggested is convenient, that's all. He is assuming you are building his projects.
You should use a buffer unless one is included in the circuit. The buffer can be an op amp circuit or other discrete type.
The lamp stabilized types have a variable distortion and level with frequency. The lamps used can be driven with an op amp, so very low current types. I do not recommend this type, but they give okay performance in a fixed frequency application. If you can find a Jfet control type the performance will be much better. To vary the frequency, you may be further ahead with an XR8038 or XR2206 types. They are much more forgiving and will work properly (for them) much more quickly.
-Chris
anatech said:
I have built a really good freq generator using an adjustable gain amplifier -- the SSM2018 was the first -- I still have a bunch of these chips if anyone cares -- this is the chip that Cyril Bateman used in his "Parts Per Billion" signal generator for the capacitor article in EW. I don't want to be accused of thread-jacking, so...
Here's the schematic of the first 'scope I built -- it was used as a monitor for my ham radio stuff back in the 1960's:
Attachments
I now realise why an sinus/tone generator is expencive, it's not just something you make out of nothing.
I think I will continue searching for a schematic. Maybe I will have to buy the expencive MAX038 chip, the one SHUSHA wrote about in post #18, but the schematics he is talking about I can't find.
Maybe someone could help me. ?
BTW: have a nice weekend all of you!
I think I will continue searching for a schematic. Maybe I will have to buy the expencive MAX038 chip, the one SHUSHA wrote about in post #18, but the schematics he is talking about I can't find.
Maybe someone could help me. ?
BTW: have a nice weekend all of you!
i think that you can do much better with discrete components, and it will be less expensive than the MAX038.
Charles Hansen described a very, very good oscillator which used a clock oscillator and a pair of Linear Tech low pass filter chips -- or --
if you can get your hands on an ancient SG501 or SG502 from Tektronix you can replace the active electronics with a pair of low noise opamps and a VGA opamp and get an oscillator with extremely low THD (fwiw, the SG505 which is now quite expensive, can achieve THD below 0.001%.) The SG501 can sometimes be had for about $20 on EBay.
Charles Hansen described a very, very good oscillator which used a clock oscillator and a pair of Linear Tech low pass filter chips -- or --
if you can get your hands on an ancient SG501 or SG502 from Tektronix you can replace the active electronics with a pair of low noise opamps and a VGA opamp and get an oscillator with extremely low THD (fwiw, the SG505 which is now quite expensive, can achieve THD below 0.001%.) The SG501 can sometimes be had for about $20 on EBay.
Well... we keep an '88 Acura around here. We use use when all the "good" cars are broken.
My silly girls didn't think I could make a radio station... It took me all of 10 minutes to patch together an FM staion and start broadcasting with my TM stuff... I love the stuff. Oh, and don't tell the FCC!
OLD!... old is relative...
My silly girls didn't think I could make a radio station... It took me all of 10 minutes to patch together an FM staion and start broadcasting with my TM stuff... I love the stuff. Oh, and don't tell the FCC!
OLD!... old is relative...
poobah said:Jack,
Could you please refer to the TM500 stuff as "time honored" rather than "ancient". I have a wall of that stuff... I really feel old now... not as old as SY but...
how about "venerable" ?
(and btw, I keep a spare 1987 MB around for spares -- with gas at $3/gal they are cheap as dirt). I have been feeding a 420 to a 560.
I bought a bunch of this stuff in the midst of the "slough of despond" (when the tech bubble burst):
An externally hosted image should be here but it was not working when we last tested it.
Hi poobah,
I don't have any other modules, so the chassis would not be useful to me. These were for calibrating 'scopes. They were taken out of service at the lab I used to work for.
$50 is very reasonable for that 4 banger. If I had other units I'd would have taken you up on it. Thank you very much for the offer.
-Chris
I don't have any other modules, so the chassis would not be useful to me. These were for calibrating 'scopes. They were taken out of service at the lab I used to work for.
$50 is very reasonable for that 4 banger. If I had other units I'd would have taken you up on it. Thank you very much for the offer.
-Chris
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