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Thanks again Randy.  Very informative.  

Frankjesco

Iron

@Randy

It seems that many of the signal conditioning ICs are now more complex than the individual op amps, etc. used in past decades.  Have you ever been bitten in production by using a single sourced IC that at first looked attractive because of special features?

Thanks to you, Lauren, Digi-Key, and Design News.

Thank you Randy. Great material on this presentation.

Iron

Thanks Randy will look at them

Iron

Thanks Randy et al!

Iron

So the Offset is the ZERO Offset for the sensor/.

That's going to do it for today.

Thanks for participating.

Blogger

Thanks Randy, Lauren & Digi-Key

Iron

What does offset indicate on slide # 4 graph ?

On slide 4 Eo is the output. On slide 5, the offset is some mV level present as Eo even if no pressure is applied to the sensor.

 

Blogger

Thank you Randy, Lauren, Digi-Key and ieee

 

software types here use matlab for signal processing...

you can used matlab to design the filters of second order for instance

Iron

Thanks, all.  I have to go.  See you tomorrow.

Platinum

you would would want a low V source IF you are trying to do something small and battery powered - think watch battery - typically 1.55Volts

Iron

78RPM, see slide 9.  It actually takes 4 op amps to complete and buffer the circuit.

Iron

When low voltage acquisition you must have low frequency signals for noise reason.

Iron

78RPM, that is typically how the sensor is connected.  Two opamps in differential mode.

Iron

Would you use MATLAB for signal processing.

This should be possible but I do not have any direct exposure to what they provide in this area.

Blogger

Thanks jamal.  I'll take another look.

Platinum

I'm thinking of two opamps that operate in a balanced line mode the way microphones are often connected. Instrumentation amps use these, too.

Platinum

78RPM The TLV2474 circuit in the slides uses just that with non inverting amplifier low pass filters. 

Iron

See you tomorrow. Have a great day.

Iron

?Randy, why the desire to go to low voltage on the sensor?  As you point out, signal to noise gets to be a problem.  Most sensors are good to 10 V for excitation.  So have a 5 or 10V front end and then you can do computation at what ever voltage you would like.

Obviously you hould use the highest/higher voltage or a common 5V power source to avoid the low voltage S/N. But there may be instances where a low voltage supply cannot be avoided.

Blogger

@ 78RPM : do you mean like a differential sensor ?

Iron

Very informative discussion.  Thank you Randy

Iron

@Randy, @Randy Frank,  Would a balanced line help with noise in low-voltage use?  It would at least help with Common Mode Rejection.

Platinum

@Randy Looking for temp and pressure sensors on flexible materials any suggestions. Its for use in medical pump & syringe applications

I am aware of companies that are working on flexible temperature sensors (http://www.thinfilm.no/news/thinfilm-acquires-kovio-technology-opens-silicon-valley-nfc-innovation-center/ ) and maybe looking forward to piezoeresistive pressure sensing but not for near term avaiablity.

Blogger

You can use a bypass filter to decrease the noise.

Randy.  Log amps have poor temperature stability or else are very expensive.  A higher voltage front end is a simpler and cheaper solution.

Iron

?Randy, why the desire to go to low voltage on the sensor?  As you point out, signal to noise gets to be a problem.  Most sensors are good to 10 V for excitation.  So have a 5 or 10V front end and then you can do computation at what ever voltage you would like.

Iron

the resistance decreases with temperature increasing or otherway round ?

how about considering the use of log amps for sensitive (down to noise-level sensing) ?

That certianly would be something to look into.

Blogger

Are there problems with low voltage excition for pressure sensors along with amplifiers and A/D designed to operate below 3 volts related to the signal to noise ratio increasing to the point where low level signals are hard to isolate from random noise?

At low signal levels, the pressure sensor itself can add to the noise, especially if dynamic waveform analysis is being perfoemed. Some signal conditioning circuits are designed to operate down to 1.8V (and perhaps lower)  so you would have to check out the noise specs on these devices at the lower signal levels and perhaps consult the mnaufacturer to see if they meet your needs.

Blogger

@ ElRoy + @Randy :
how about considering the use of log amps for sensitive (down to noise-level sensing) ?

Iron

Would you use MATLAB for signal processing.

Thank you Randy for another great lecture.

Iron

StephT go to archive and click the archive link for yesterdays slides

What does offset indicate on slide # 4 graph ?

 

kaddaem, the typical solution for medical like that, is to use a rubber/gel interface to couple to a MEMS piezoresistive sensor.  Sensors are available with some of these or all of these features.

Iron

(sorry, Internet dropped out...)

I will look at specs, pricing, App Notes, gerbers before eval kits ; if available, fine, but not a deal beaker ; free samples are a nice offering !  ;-)

 

Iron

Randy I missed yesterday's session because of a meeting obligation. Is the audio availabe to listen in such a situation?

You should be able to access it by clicking on that day.

Blogger

Do you consider the Golden Rules when building op amps?

@Randy Looking for temp and pressure sensors on flexible materials any suggestions. Its for use in medical pump & syringe applications

Iron

@ieeerudy, You can get yesterday's audio from the same place you got today's audio.  Just select Day 1 instead of Day 2.  Otherwise, you can go to Archived Classes to the right of the Digi-Key logo.

Platinum

TI has very good develoment kits for sensor designs.

Iron

Hi Good afternoon. Sorry I am late, due to network problems.

 

@StephMcGUBM.  Thanks for the tip to re download the slides

Iron

good programming analog front end options

 

Iron

Randy please when you talk about EV KIT give us your view on TI PGA400-EP and there is EVM for it

Iron

DreamsToReality, the term Piezo has a couple uses.  Piezo resistive is just a strain gage and is good down to DC.  Piezo electric does have a lower frequency cut off and is strongly dependent on the signal conditioner input impedance.

Iron

?Randy: What have you used most often to linearize a nonliner sensor output?

Iron

@Randy

Are there problems with low voltage excition for pressure sensors along with amplifiers and A/D designed to operate below 3 volts related to the signal to noise ratio increasing to the point where low level signals are hard to isolate from random noise?

Iron

What type of formulas do you use to get these figures?

For the linearity calculations check out:

http://www.allsensors.com/engineering-resources/white-papers/linearity-measurements-pressure-sensors

Blogger

Thanks Lauren and Randy

Iron

Thank you Randy and Lauren for this class.

Randy, Lauren,

Thank you

Iron

What role does an evaluation or development kit play in your selection of a sensor or IC: from a little (0) to a lot (10)?

7. Always it is possible, I prefer to evaluate.

@Randy Thanks

Will be sure to look more into eval kits may be useful 

Iron

Comment on slide 3...I believe signal integrity better belongs on the first level preferably before amplification.

Iron

Randy and K-9,

thanks for another good presentation.

Iron

(oops) Thanks Randy and Lauren...

Iron

@Randy  Give us an idea of what parameters are different with piezo resistive versus other types.  For example, in strain gauge work, piezos seem to have a strong frequency bias toward higher frequencies.

Thanks Rangy. It is a nice overview of the interafce circuits.

Iron

Tanks Randy.

Feed that dog

great info, thank you

Iron

Randy I missed yesterday's session because of a meeting obligation. Is the audio availabe to listen in such a situation?

Iron

Thanks Rand and Lauren...

Iron

Thank you!!!! Appreciate the info on Eval Kits.

Iron

Thanks for the presentation!

Iron

Thank you Randy and Lauren

I liked the exposure to various chips to look at.  Thank you

Iron

Thanks Randy and those at Digikey

 

Thanks Randy. Great presentation.

Iron

Thanks Randy and Lauren

Iron

Thank you Randy & Lauren

Iron

cannie wants to play..

I really don't use many eval kits so far since I'm just learning about MCUs.

Iron

Another great lecture. Thanks Randy.

What is the name of your dog? another tech listener?

Iron

Thanks!
very useful comments added to the slide.

Iron

someone passing by your house

Iron

thanks for the information!  Thanks Randy

Iron

Thank-you for your presentation.

Iron

Thanks Randy, very informative.

Iron

Thanks, very interesting. 

 

Iron

Thanks Randy, Lauren & Digi-Key! Very interesting!

Iron

Thank you Randy, Lauren, and Digi-Key

Platinum

Thanks Randy and Lauren.

Iron

thanks Randy and Lauren

Iron

Thanks for the presentation.  Listening again tomorrow.

Iron

Good Dog! (pats head)

Iron

Great presentation, thank-you.

Iron

We are on slide 21. 

Platinum

the more complex, the more useful

Canine Sensor Unit activation...

Iron

I would say a kit would play 3 - 7 with norm of 5.  depends on kit and time frame.  when time is critical bigger role.

 

 

Iron

TPIC83000-Q1 directly connects without filtering 

Iron

We are on slide 18.

Platinum

8/10 for evaluation kit

Iron

We are on slide 17.

Platinum

only buy complete packaged sensors - so dev kit =0

Iron

We are on slide 16. 

Platinum

Will use eval kits first, if thy're available

Iron

evaluation kit not very important here, but most projects are hobby (cost-sensitive). I say 3 since an example circuit is always welcome

Depond of project.Eva kit can be useful.

Iron

Eval kits can be very important as we often start projects before funding, eval boards and samples provide a least cost way into engineering a proof of concept.  This often translates to basis for BOM if all requirements are met.

Iron

Important if price is reasonable

Iron

Eval Kits are very useful

Iron

Ok I'm finally in after login in with FF

Iron

only buy sensors with breakout boards or eval kits.

Iron

We are on slide 15.

Platinum

Evalution kit gives confidence on the device.

Iron

9/10 always good to have a baseline circuit to compare

Iron

Dev/Eval Kit value - about 8

Iron

I almost never use eval kits

Iron

Evaluation kits are a big plus and lets me bring up a proof of concept quickly. I'd rate it an 8 out of 10

An evaluation kit allows wringing out a potential choice of pressure sensor implementation

7.  The eval kit is very useful.

Iron

Very important due to verification of sensor characteristics.

Iron

2. evaluation kits are sometimes useful, but generally contain overly broad capabilities that make it hard to fit into a specific application.

Iron

The availability of evaluation kits impacts the decision a lot.

 

Iron

Eval kit is usually important in order to save time.

Randy's question was: What role does an evaluation or development kit play in your selection of a sensor or IC: from a little (0) to a lot (10)?

Platinum

eval kit available and reasonably priced is very important for chip eval and selection

Iron

Randy's? if available, always like eval boards. 9

evelaution kits are great

Iron

importance of an evaluation kit is high - 8 to learn about the deivce before implementations

Iron

On a scale of 0 -10, the kit ranks around 4, desireable but far from essential.

Eval kit does not really rate into selection, but if one is available, I'll use it to speed development.

Iron

current/voltage and speed

Iron

Eval kits are very important since they allow me to evaluate a new device very quickly

Iron

Very useful  A 10

Iron

Evaluation kit-->2 never used it

Eval Kits help a lot, 8, as we always need a proof of concept and breadboard it up.

Iron

7 - important to consider.

Iron

a lot, we test most things before committing to a design 8/10

Iron

Evaluation kits for me make it easier to test a device. I'd give it an 8

Iron
for MAX1450 laser trimming resistors is used, right?
Iron

Evaluation kits are very important.

Iron

Evalutation kit is very important

Iron

I often buy an eval kit before selecting specific product

Platinum

Use eval kits quite often to get an idea of what's out there to use in projects. Very helpful in design work here.

Iron

A lot - I like to work with a new sensor in a known working circuit

Iron

We are on slide 14.

Platinum

depends on project, can be extremely useful. 

Iron

8.  Always try to eval first.

Iron

does the sigma mean the sum of all voltages

I have used an INA125 for Pressure Transducer Applications. It is an instrumentation Amp with a built in Precision Voltage Reference for stability across the bridge.

Iron

Best fit with limited polynomial compensation or look-up table when required.

Iron

@rswamson - Please download the slide deck again. My slide #7 is not blank.

We are on slide 13.

Platinum

in integrated circuit, very useful

Best fit linearity

Iron

We are on slide 12. 

Platinum

rt = rise time?

 

Iron

usually not concerned with dT/dt as temperature changes are relatively slow.  More concerned with accuracy and some times noise rejection.

Iron

We are on slide 11. 

Platinum

For now, no linearity I have to use

how does q1 transistor help on slide 9

 

Iron

use golden rules to solve for these types of circuits

MY SLIDE 7 IS BLANK, SO NOW WE ARE OFF BY ONE SLIDE NUMBER TO THE ONES THAT RANDY IS USING.

Iron

We are on slide 10. 

Platinum

How fast do the sensers get the signal its detecting

Both Current and Voltage  sensosr

Iron

Span, initial offset and lineatity

Iron

Not required at this time.

Iron

usually least squares but have used excel higher degree regression of raw data.

Iron

The instrument grade pressure sensors are less than 1% off for all cases.  The disposables are maybe 2 or 3 % worst case?

Iron

we use a 2-10 Volt signal or a 4-20mA and use 8bit and 10 bits A/D and D/A. Straight line with 5% error

Iron

Beyond the data acquisition and sensor compensation, what type of information or knowledge are you looking for from the sensor?

Current and voltage sensing. Also frequency and speed.

 

linearity most used.

Iron

We use least squares fit.

least squared fit?

 

Iron

Linearity over a specified range as a function of output, i.e. +/- 0.5 degree. 

Iron

What type of formulas do you use to get these figures?

 

piecewise linearization and LUT

Iron

Linerarity: I buy the linearity that my pocket can afford.

Iron

No linearity requirements at present

 

Iron

Randy's? all ways best fit..

best fit two point calibration

Iron

Frequently linearity is acceptable.  When not, use some sort of tabular interpolated correction.

Linear position pots

Iron

Best fit straight line

No specific linearity is requested. Best-fit is usually adequate

Iron

very little sensing required, so not much need for linearity specifics

I need to force a fit through the zero point

Iron

A lookup table or range testing

Platinum

linearity makes the implementation of software algorithms easier!

Iron

have not specifiied linearity yet

Iron

Air pressure measurement.

piecewise BFSL segments as long as there are no Y reversals vs X

Iron

Depends on project

Iron

Linearity not required.

Iron

Randy's question was: What type of linearity do you usually use or specify?

Platinum

Voltage and current level sensing

Iron

Interface for piezoresistive with sensitivity to temperature variations

Iron

what does the nonlinearity refer to the signal?

Primarily data acq

 

Iron

Temperature & control sensing

Iron

I buy already compensated pressure sensors.

Iron

acoustic effects such as combustion rumble

Iron

P-V curve validation

Iron

what is span? = range?

Iron

humidity, temperature, black body radiational factors.

 

Iron

calibration and response time

Iron

easier ways to calibration 

Iron

data aq. to control.

 

Iron

usually state of a machine. sensors are used to adjust gain of a control system or schedule activity

Iron

water depth, and temperature data aqd.

Iron

action upon changes in sensed data

Iron

acceleration, pressure and temperature

Iron

Characterizing th object under test thru it's operating environment.

Iron

data acquisition and sensor compensation, that is pretty much it. Sometimes a programmable analog front end with some memory to save a default configuration

Iron

Precise calibration.

Iron

I am now using pressure sensors that also report Temperature (dual output)

Iron

I am looking for reliability and accuracy

Iron

@vijenad, Did you turn up the volume bars at thre right of the Audio bar?

Platinum

My application experience is on weight of moving objects

Iron

Generally blood pressure waveform, need about 20 Hz minimum frequency response.

Iron

In the future, frequency

Iron

Pressure extremes would be defined and applied to the state machine for critical decisions

 

mostly two levels but some sensor fusion as well

Iron

Low speed data acq.

 

Iron

Typically calibration, linearization (where needed), and sometimes sensor fusion.

Iron

Prediction and pattern recognition. Some sensor fusion.

Diagnostics & Noise Removal

Iron

I'm interested in noise removal and patter recognition techniques

Iron

Data aquisition and display

Iron

Environmental factors such as: pressure, temp, humidity.

Iron

repeatability and hysterisys

 

Iron

information to send out alarms

 

Iron

Pattern recognition.

Iron

Just for data acquisition

 

I'm learning what kind of knowledge is available.

Platinum

time series, ML and prediction, ...

Iron

Pressure at a low rate

Iron

Environmental limitations and choices among sensors

Strictly data aq.

Iron

I'm getting audio OK on my laptop (for what it's worth).

Iron

Randy's question was: Beyond the data acquisition and sensor compensation, what type of information or knowledge are you looking for from the sensor?

Platinum

Hello from Orlando, FL

Iron

plenty of volume here.  check the player settings as well as pc

Iron

hi from Lincoln NE

Iron

I see the audio bar

Iron

Hello,

I am on maximum volume on my Laptop, its not so audible.  Is there any way to increase audio volume at your end

 

Iron

audio is live now 

Iron

well I haven't seen the audio bar

Iron

Hello everybody from Guadalajara Mexico

Hello from Montreal (#2)

 

Iron

Hell from Orlando, FL

Iron

Hello from Montreal, QC

Iron

Hello fron Oviedo, Spain

Iron

Hello from W. Caldwell NJ

Iron

Hi all -Audio is live! If you don't see the audio bar at the top of the screen, please refresh your browser. It may take a couple tries. When you see the audio bar, if it doesn't start automatically, hit the play button. If you experience audio interruptions and are using IE, try using FF or Chrome as your browser. Many people experience issues with IE. Also, make sure your flash player is updated with the current version. Some companies block live audio streams, so if that is the case for your company, the class will be archived on this page immediately following the class and you can listen then. People don't experience any issues with the audio for the archived version.

hello from Houston TX

Iron

Hi from Panama City, FL.

Iron

Hi from Rocklin, CA

Iron

Hello from Kansas City

Checking in from Thornville Ohio

Iron

greetings from slc ut...

Good day to every one form Culiacan, Mexico

Hello from Cedar Park Texas

Iron

Hello from Co Springs!

Iron

Hello from Winston-Salem

 

Iron

Greetings from Saginaw, MI

Good morning from Valdez

Good afternoon from a sunny and warm Minnetonka, MN.

Iron

Hi. We will be starting soon

Blogger

Another hello from Albuquerque

Hello from Chicago

Iron

Hello from Albuquerque.

Iron

Hello from Kansas

Iron

Hello from Corona Ca.

Iron

 

hello from Mishawaka

 

Iron

Hello from Longmont, CO

Iron

hello everyone from Timisoara, Romania

Iron

You are eligible to earn IEEE Professional Development Hours by attending these courses and participating in the chat function. Additionally, we are no longer using the points system, offering "graduation", or giving grades. The IEEE hours are taking the place of that. There are some important things for you to know about earning the hours. The most important ones are that you need to attend these courses live, you need to attend a minimum of two of them per semester, you need to fill out a course evaluation form within 2 weeks of the end of the class, you need to attend 4 out of the 5 classes per course, and you need to participate in the chat function every day you attend. Please click on the link at the top of this page that says "How do I earn IEEE professional development hours" to read all of these important details and more.

Platinum

Good morning from San Ramon, CA

I don't know how to join linkdin group.

Iron

Please join our Digi-Key Continuing Education Center LinkedIn Group at http://linkd.in/yoNGeY and be sure to follow @designnews and @DigiKeyCEC on Twitter for the latest class information. We encourage you to tweet about today's class using #DigiKeyCEC.

Platinum

Greetings from Buffalo, NY!

Iron

Hi there, from Goiania/GO, Brazil

Iron

Good afternoon everybody

The streaming audio player will appear at the top of this web page when the show starts at 2 PM Eastern time today. When you see it, click on the play button to start the audio. Note however, that some companies block live audio streams. If when the show starts, the audio bar doesn't appear or you don't hear any audio, try refreshing your browser. If that doesn't work, try using Firefox or Google Chrome as your browser. Some users experience audio interruptions with IE. Also, make sure your flash player is updated with the current version. If that doesn't work, the class will be archived immediately following our live taping. You shouldn't experience any problems with the audio when listening on-demand.

Platinum

gorgeous Houston here....

Iron

Hello from Dallas, TX

Iron

Be sure to click 'Today's Slide Deck' under Special Educational Materials above right to download the PowerPoint for today's session.

Platinum

I am looking forward for another great lecture.

Iron

Hello Randy and Lauren. How are you?

Iron

hello from the midwest

Iron

Signing in from COS

Iron

Aloha from warm sunny nortwest Montana

Platinum

Greetings from Somewhere on the Niagara Frontier.

Iron

Hello from cloudy Rochester, NY, USA

Hope all is well.

Iron

Hello from Chicagoland

Iron

How is everyone doing?

Iron

Hello from Summerville, SC

Iron

Hi,

Frank what is today's Slides

Iron

Hello from sunny SE Lake Simcoe Ontario Canada.

Iron

HELLO FROM SW MICHIGAN

Iron

Greetings from Plymouth, MN!

Iron

Good morning from sunny Edmonton, AB

Iron

Good From Ghana @ work for Claas Day 2

Iron


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