"Bruno Richard" <bruno.richard.fr@gmail.com> wrote in message news:1181030631.316540.197960@g4g2000hsf.googlegroups.com...> Hi all, > > I am working on a project where I need some 16 bits ADC to retrieve > information from a sensor. I also need a small microcontroller such as > a PIC, AVR or 8051, and I got surprising quotes for the ADC: Around $5 > (qty 1000), which is 5 times more expensive than the controller! > > Does anyone have an idea about how I can get some low cost ADC- > Controller solution? I need only few dozens of samples per second, so > some of you may have nice tricks to do that (op-amps, capacitor charge > time stuff and the like). > > Thanks, Bruno >How about the AD7143 @ $1.24 for 1000pcs. 43.5 SPS, 3.3mW, 8 channel, 4mm x 4mm package. Thomas
16-bits ADC anyone?
Started by ●June 5, 2007
Reply by ●June 5, 20072007-06-05
Reply by ●June 5, 20072007-06-05
On Tue, 05 Jun 2007 08:03:51 -0000, Bruno Richard <bruno.richard.fr@gmail.com> wrote:>I am working on a project where I need some 16 bits ADC to retrieve >information from a sensor. I also need a small microcontroller such as >a PIC, AVR or 8051, and I got surprising quotes for the ADC: Around $5 >(qty 1000), which is 5 times more expensive than the controller!The problem with microcontrollers with on-chip ADC/DACs is that you might not get the nominal 98 dB SNR due to the noise from the controller. Is DC accuracy (drifts) important in your application ? Is this ADC part of a control loop, in which case it would be preferable that the ADC is monotonous. Paul
Reply by ●June 5, 20072007-06-05
Paul Keinanen wrote:>>I am working on a project where I need some 16 bits ADC to retrieve >>information from a sensor. I also need a small microcontroller such as >>a PIC, AVR or 8051, and I got surprising quotes for the ADC: Around $5 >>(qty 1000), which is 5 times more expensive than the controller! > > > The problem with microcontrollers with on-chip ADC/DACs is that you > might not get the nominal 98 dB SNR due to the noise from the > controller.Besides, the high performance ADCs and the microcontrollers are the two different technologies. The MCUs with the good ADC/DACs usually contain two separate dies in one package. For that reason they are more expensive then the equvalent micro + equvalent ADC/DAC.> > Is DC accuracy (drifts) important in your application ? > > Is this ADC part of a control loop, in which case it would be > preferable that the ADC is monotonous.I am wondering of what could be a sensor which requires the ADC with the true 16-bit accuracy. For the sensor application, that sounds unreasonable to me. Especially considering that the rest of application is handled by a small micro. Apparently there is a problem with the concept. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
Reply by ●June 5, 20072007-06-05
On Wed, 06 Jun 2007 00:28:50 +0300, the renowned Paul Keinanen <keinanen@sci.fi> wrote:>On Tue, 05 Jun 2007 08:03:51 -0000, Bruno Richard ><bruno.richard.fr@gmail.com> wrote: > >>I am working on a project where I need some 16 bits ADC to retrieve >>information from a sensor. I also need a small microcontroller such as >>a PIC, AVR or 8051, and I got surprising quotes for the ADC: Around $5 >>(qty 1000), which is 5 times more expensive than the controller! > >The problem with microcontrollers with on-chip ADC/DACs is that you >might not get the nominal 98 dB SNR due to the noise from the >controller.>Is DC accuracy (drifts) important in your application ? > >Is this ADC part of a control loop, in which case it would be >preferable that the ADC is monotonous. > >PaulITYM "monotonic"-- did a spell chequer get you? ;-) Making a slope-type ADC with ~16 bit resolution isn't all that hard, nor is adding some dither and oversampling with a successive- approximation type converter. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Reply by ●June 5, 20072007-06-05
On Wed, 06 Jun 2007 00:28:50 +0300, Paul Keinanen <keinanen@sci.fi> wrote:>The problem with microcontrollers with on-chip ADC/DACs is that you >might not get the nominal 98 dB SNR due to the noise from the >controller.Some of the newer microcontrollers such as the MSP430 get around this problem by using very low power operation. Others take their samples while the microcontroller is in sleep mode.
Reply by ●June 6, 20072007-06-06
Vladimir Vassilevsky wrote:> I am wondering of what could be a sensor which requires the ADC with the > true 16-bit accuracy. For the sensor application, that sounds > unreasonable to me. Especially considering that the rest of application > is handled by a small micro. Apparently there is a problem with the > concept.Plenty of sensors are read with 16-bit ADCs. Examples: pressure sensor, strain gauge, position sensors, etc. Just take a look at the Analog Devices app notes.
Reply by ●June 6, 20072007-06-06
On 2007-06-06, mw <mw@avoidspam.com> wrote:> Vladimir Vassilevsky wrote:>> I am wondering of what could be a sensor which requires the >> ADC with the true 16-bit accuracy.Plenty of them.>> For the sensor application, that sounds unreasonable to me. >> Especially considering that the rest of application is handled >> by a small micro. Apparently there is a problem with the >> concept. > > Plenty of sensors are read with 16-bit ADCs. Examples: pressure sensor, > strain gauge, position sensors, etc. Just take a look at the Analog > Devices app notes.I know of quite a few applications that are using 20 and 24 bit ADCs. 16 bits really isn't pushing the limits at all. -- Grant Edwards grante Yow! hubub, hubub, HUBUB, at hubub, hubub, hubub, HUBUB, visi.com hubub, hubub, hubub.
Reply by ●June 6, 20072007-06-06
On Wed, 06 Jun 2007 04:32:35 -0000, the renowned Grant Edwards <grante@visi.com> wrote:>On 2007-06-06, mw <mw@avoidspam.com> wrote: >> Vladimir Vassilevsky wrote: > >>> I am wondering of what could be a sensor which requires the >>> ADC with the true 16-bit accuracy. > >Plenty of them. > >>> For the sensor application, that sounds unreasonable to me. >>> Especially considering that the rest of application is handled >>> by a small micro. Apparently there is a problem with the >>> concept. >> >> Plenty of sensors are read with 16-bit ADCs. Examples: pressure sensor, >> strain gauge, position sensors, etc. Just take a look at the Analog >> Devices app notes. > >I know of quite a few applications that are using 20 and 24 bit >ADCs. 16 bits really isn't pushing the limits at all.Anyway, he didn't specify what the accuracy was. 16 bit resolution is pretty unremarkable for control applications. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Reply by ●June 6, 20072007-06-06
mw wrote:> Vladimir Vassilevsky wrote: > >> I am wondering of what could be a sensor which requires the ADC >> with the true 16-bit accuracy. For the sensor application, that >> sounds unreasonable to me. Especially considering that the rest >> of application is handled by a small micro. Apparently there is >> a problem with the concept. > > Plenty of sensors are read with 16-bit ADCs. Examples: pressure > sensor, strain gauge, position sensors, etc. Just take a look > at the Analog Devices app notes.Yes, but the question is why? That gives a result to 1 part in 65535 over the range, and even if we assign the high order bit to allow overruns by a factor of 2, it is still 1 part in 32767. I find such precision requirements to be extremely rare. -- <http://www.cs.auckland.ac.nz/~pgut001/pubs/vista_cost.txt> <http://www.securityfocus.com/columnists/423> <http://www.aaxnet.com/editor/edit043.html> <http://kadaitcha.cx/vista/dogsbreakfast/index.html> cbfalconer at maineline dot net -- Posted via a free Usenet account from http://www.teranews.com
Reply by ●June 6, 20072007-06-06
"CBFalconer" <cbfalconer@yahoo.com> wrote in message news:466659E8.2AB9A675@yahoo.com...> mw wrote: >> Vladimir Vassilevsky wrote: >> >>> I am wondering of what could be a sensor which requires the ADC >>> with the true 16-bit accuracy. For the sensor application, that >>> sounds unreasonable to me. Especially considering that the rest >>> of application is handled by a small micro. Apparently there is >>> a problem with the concept. >> >> Plenty of sensors are read with 16-bit ADCs. Examples: pressure >> sensor, strain gauge, position sensors, etc. Just take a look >> at the Analog Devices app notes. > > Yes, but the question is why? That gives a result to 1 part in > 65535 over the range, and even if we assign the high order bit to > allow overruns by a factor of 2, it is still 1 part in 32767. I > find such precision requirements to be extremely rare.I'm use to processing photosensor data. Photodiodes can be linear over a huge dynamic range - I was told 14 decades but I've only tried six. I typically want 10-bit accuracy, so some of this can be handled with a gain switch. I've processed temperature sensor data with 0.001�C resolution (but less accuracy), required for good closed loop performance. Audio data is another that needs good linearity but can tolerate scale errors. But I would help if the OP explained what he wanted the ADC for so that we can assess what aspects of the system require 16-bitness. -- Peter
