[volt-nuts] ***SPAM*** Re: Some questions to zeners (1N823-1N829)
The ADS1282 offers outstanding specification, but not very useful in the wide-scale DVM application range due to low input and reference voltages. Within a year I'm trying to develop a design of the selfcal 7.5-digits DMM with ADS1282 ADC. Reference (+/- 10V) is a aged 1N829A with 0.03ppm noise and 2nd order TC correction, downscaled to +/-2.5 V with zero TC divider. Mickle T. 29.01.2013, 11:38, Poul-Henning Kamp p...@phk.freebsd.dk: Content-Type: text/plain; charset=ISO-8859-1 In message AA473A4936944A1199FC6F4C9C5D9A1A@laptop, Andreas Jahn writes: Amazing! Recently I came across a very interesting ADC from TI, designed for use with geophones: ADS1282 It might be interesting for volt-nuttery: It samples 2 bits at 4MHz, which are then downsampled to 31 bits at 4kHz or less. For this reason it is incredibly linear and has very good S/N. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] 7081 AC buffer *again*
I've returned to the 7081 that was giving me troubles in the AC buffer circuit. Probing the output test point (TP 705) I'm seeing about 100mV pp (approx) at about 10MHz. This would likely explain the strange results I was getting last year. However I'm puzzled as to where it can be coming from!!! Any suggestions gratefully received. Regards, David Partridge ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] ***SPAM*** Re: Some questions to zeners (1N823-1N829)
The ADS1282 is a really cool part! After studying the ADS1282 datasheet is appears that *at best* it can achieve 130dB SNR which, by my calculations is effectively 21.3 bits - by the formula SNR=(6.02N+1.786)dB. This got me thinking, are there any higher performing 24 bit ADCs we should look at for our nuttery. One that I found is the Linear LTC2440 (and others in the family). It claims, at its highest resolution, 24.6 effective bits. That said, I am having trouble comparing SNR directly. I need to read more to understand how to convert its noise spec - 200nV RMS noise - to a SNR dB figure. Andy Bardagjy bardagjy.com On Tue, Jan 29, 2013 at 4:43 AM, Тимофеев Михаил timk...@yandex.ru wrote: The ADS1282 offers outstanding specification, but not very useful in the wide-scale DVM application range due to low input and reference voltages. Within a year I'm trying to develop a design of the selfcal 7.5-digits DMM with ADS1282 ADC. Reference (+/- 10V) is a aged 1N829A with 0.03ppm noise and 2nd order TC correction, downscaled to +/-2.5 V with zero TC divider. Mickle T. 29.01.2013, 11:38, Poul-Henning Kamp p...@phk.freebsd.dk: Content-Type: text/plain; charset=ISO-8859-1 In message AA473A4936944A1199FC6F4C9C5D9A1A@laptop, Andreas Jahn writes: Amazing! Recently I came across a very interesting ADC from TI, designed for use with geophones: ADS1282 It might be interesting for volt-nuttery: It samples 2 bits at 4MHz, which are then downsampled to 31 bits at 4kHz or less. For this reason it is incredibly linear and has very good S/N. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Comparing ADS1282 (31 bit) and AD7190 (24 bit)
---Original Message--- From: Poul-Henning Kamp p...@phk.freebsd.dk ...a very interesting ADC from TI, designed for use with geophones: ADS1282 31 bits is impressive. With the +/-2.5 V reference I gather the maximum input range in differential mode is Vref/2 or +/- 1.25 V. The Voffset drift is 0.02 uV/C typical and the INL is 0.5 ppm typical, but 4 ppm max. For comparison, the 24-bit Analog Devices AD7190 claims typical Voffset = 0.1 uV/C, or 0.005 uV/C in chop mode, and INL = 1 ppm typ. and 5 ppm max, with a maximum differential input voltage of +/-5 V. So the AD7190 has 2x worse INL (typ.), but with a 4x larger input voltage range, the INL is 2x better (typical) and almost 4x better (max) when measured in microvolts. For quantity 1 purchase, the AD7190 is $11 (Newark/Element14) and the ADS1282 is $62 (Arrow). For $62, you can get a complete eval board for the AD7190 which works as a 4-channel input standalone USB-powered voltmeter (although the eval board's ADR421 2.5V reference is not volt-nut quality.) By the way, the 7190 chip provides for two selectable, independent differential Vref inputs, which are separate from the two differential or four pseudo-differential signal inputs. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] 7081 AC buffer *again*
Is it possible that it is, somehow, 'picking up interference' from your 'house standard'? How close to 10.000 000 000 MHz is it? 100 mV P-P is fairly substantial. Otherwise, is it oscillating? Good luck. Joe -Original Message- From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On Behalf Of David C. Partridge Sent: Tuesday, January 29, 2013 9:54 AM To: 'Discussion of precise voltage measurement' Subject: [volt-nuts] 7081 AC buffer *again* I've returned to the 7081 that was giving me troubles in the AC buffer circuit. Probing the output test point (TP 705) I'm seeing about 100mV pp (approx) at about 10MHz. This would likely explain the strange results I was getting last year. However I'm puzzled as to where it can be coming from!!! Any suggestions gratefully received. Regards, David Partridge ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
