B14 Glass Vacuum Heated Thermistor STC, c.1963 10KΩ @20degC Rare, Cool, Made in UK | eBay
Are these indirectly heated thermistors any good for Wien bridge oscillator building?
I'm after a replacement for a RA15 and these have come up, I'm wondering whether with some rejigging of resistor and capacitor values in the rest of the circuit it might work?
Are these indirectly heated thermistors any good for Wien bridge oscillator building?
I'm after a replacement for a RA15 and these have come up, I'm wondering whether with some rejigging of resistor and capacitor values in the rest of the circuit it might work?
Excuse my suspicious nature but the original glass AUDIO grade thermistors of which I have two in old equipment I built at the time to JLH designs are like "Gold Dust " and IF----- yes IF somebody on eBay is selling them at £3 nothing --yes nothing would make me buy them.
The electrical standard for use in a THD meter is very high as is a high quality audio signal generator --and yes I built several to designs in EW that those advertised what is it they say in the USA ?--- there,s a S----r born every minute -REAL ones --and the last price I saw a long time ago was extortionate are as scarce as Medusa,s Head.
Buy the eBay ones and build a Wien Bridge?---sure you can just don't expect very low distortion figures .
Of course this is my personal opinion but I am sticking to it.
The electrical standard for use in a THD meter is very high as is a high quality audio signal generator --and yes I built several to designs in EW that those advertised what is it they say in the USA ?--- there,s a S----r born every minute -REAL ones --and the last price I saw a long time ago was extortionate are as scarce as Medusa,s Head.
Buy the eBay ones and build a Wien Bridge?---sure you can just don't expect very low distortion figures .
Of course this is my personal opinion but I am sticking to it.
Ok, I bought one anyway... 
http://electrojumble.org.uk/DATA/STC_B_&_R_Thermistors.pdf
I have a signal generator that uses a second thermistor for ambient temperature compensation, I’m hoping this can be hijacked to power the heater.
http://electrojumble.org.uk/DATA/STC_B_&_R_Thermistors.pdf
I have a signal generator that uses a second thermistor for ambient temperature compensation, I’m hoping this can be hijacked to power the heater.
No, the idea behind the thermistor in a Wien bridge is that the resistance drifts
as a function of the AC signal so the loop gain can be corrected.
Stabilizing its temperature would inhibit that.
Gerhard
I am amazed at some comment here ,obviously I live in an alternative universe and obviously I didn't build JLH,s distortion analyzer way back then that could reduce distortion down to 0.001 % --that's right =0.001 % -- NO digital help -no "fets " -all done by HAND -- now ridiculed I see .
Guess what the stabilizing component was ??? - oh no ! not a -yikes ! - a thermistor but not your ordinary eBay/Amazon rubbish of 2021-- a real audio one .
I will now dig it out -but maybe it was all my imagination yes that must be the answer and I wont find it .
Do you honestly think what was brought up here and criticised had not already been compensated for at the time in the pages of TOP UK electronic magazines ?
Guess what the stabilizing component was ??? - oh no ! not a -yikes ! - a thermistor but not your ordinary eBay/Amazon rubbish of 2021-- a real audio one .
I will now dig it out -but maybe it was all my imagination yes that must be the answer and I wont find it .
Do you honestly think what was brought up here and criticised had not already been compensated for at the time in the pages of TOP UK electronic magazines ?
In high end broadcast and time signal equipment, temperature controlled housings for crystals were used, but I have never heard of those in commercial equipment, in that those systems were to be used by ordinary users.
Think white coats, laboratory, highly educated staff, with the equipment to check and control deviations, and temperatures maintained within 0.1 Celsius.
If you wish to be very precise, a crystal is the easy way, rather than a thermistor or whatever, in that you need a precise frequency.
And divider / multiplier chips, and even synthesizer chips are available.
Think white coats, laboratory, highly educated staff, with the equipment to check and control deviations, and temperatures maintained within 0.1 Celsius.
If you wish to be very precise, a crystal is the easy way, rather than a thermistor or whatever, in that you need a precise frequency.
And divider / multiplier chips, and even synthesizer chips are available.
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"an audio oscillator doesn't need frequency precision ( quote ) .
Of course it doesn't that's why its never been used in the past to adjust/make precision filters - as I keep saying its a different thinking world now that only seems to have started 10 years ago --before that -who knows - brick building - cooking .
For Pingrs --- for the record I was able to make an ANALOGUE oscillator that could be set very accurately - 10 turn Bourns pot to precisely the frequency I wanted to check on various oscillations / unevenness in audio test equipment of one sort or another .
Come on I know the aim is to dis history but I thought at least Engineering on an engineering website and those involved with it would at least recognize previous/past achievements or does "learning " start in 2021 ?
Of course it doesn't that's why its never been used in the past to adjust/make precision filters - as I keep saying its a different thinking world now that only seems to have started 10 years ago --before that -who knows - brick building - cooking .
For Pingrs --- for the record I was able to make an ANALOGUE oscillator that could be set very accurately - 10 turn Bourns pot to precisely the frequency I wanted to check on various oscillations / unevenness in audio test equipment of one sort or another .
Come on I know the aim is to dis history but I thought at least Engineering on an engineering website and those involved with it would at least recognize previous/past achievements or does "learning " start in 2021 ?
Thank you Gerhard.
I hadn’t realised that the non-Ohmic behaviour is a function of the cold/hot change rather than a question of degree in the presumably ohmic “hot” state.
It makes sense, it seems that this thermistor is indeed no good for what I want.
No. "Learning starts" on UTubeBook and the 13 second attention span.
Your fact-based universe is now an alternate reality, as you say.
Johno's post requires more than 13 seconds of re-design but is a fine answer.
Oh come on David ---the 8038 ?? this is engineering politics at work .
Down market electronics back then was awash with "audio circuits " using that --"want to build your own audio signal generator "just like the professionals " - get our 8038 based - do it all waveform generator --just add a few parts etc etc etc.
What some of the more unscrupulous ones advertised ( or "forgot " to ) was that it even then it was nowhere up to top spec.and was meant for -shall we say learners ?.
Dont know anybody on EW who personally used it and putting down Audio Precision ?--I am sure member D.Self would have something to say about that he mentioned it every 5 minutes in EW.
And does your DAC do all the audio tests that the AP does ? --with the same precision ?
Down market electronics back then was awash with "audio circuits " using that --"want to build your own audio signal generator "just like the professionals " - get our 8038 based - do it all waveform generator --just add a few parts etc etc etc.
What some of the more unscrupulous ones advertised ( or "forgot " to ) was that it even then it was nowhere up to top spec.and was meant for -shall we say learners ?.
Dont know anybody on EW who personally used it and putting down Audio Precision ?--I am sure member D.Self would have something to say about that he mentioned it every 5 minutes in EW.
And does your DAC do all the audio tests that the AP does ? --with the same precision ?