Precision Data Converters

Forum Post: RE: ADS1158 Specification Errors?

Jeffery Pfarr — Fri, 24 May 2013 16:43:00 GMT

Scott,

The 100 uF cap in parallel w/.1 uF is part of the DC single pole filter for the reference. For an optimum DC filter, these values are correct as specified. The REF5040 in Fig. 54 is correct and matches the Typical conditions specified in the Electrical Charactistics table. The text referring to the REF3125 and Vref = 2.5 V is in error but that reference could be used as well since its within the allowed range specified in the Electrical Characteristics table. Note that the AIN and ADCINP - ADCINN voltage maximums are per the Electrical Characteristics Table.

Forum Post: RE: ADS1299 Wiring & Start

Chuchaki — Fri, 24 May 2013 11:19:00 GMT

Good Day again. I'm not sure if my Question is stupid or to much to ask for, but i would apreciate a comment on this topic. Here are some Scope images..

SDATAC

Set internal Reference:

Read Register:

and nothing on the MISO....

Forum Post: ADS129x - reading ID of chips in daisy chain configuration

Filip Kinovic — Fri, 24 May 2013 11:02:00 GMT

Hello,

I am using precision A/D converters ADS1298 and ADS1294 in my project with STM32F4. I control multiple converters in daisy chain configuration. I am able write registers and read continuous data. I can read registers from first chip, but I don't know if it is possible to read registers other devices in the chain. Actually, I would like to read ID of all devices (dynamical channel detection) and to check that all registers are set correctly.

I didn't find any note in manual that it is or is not possible. I tried to read ID from multiple devices without success.

Is it possible to read registers from multiple devices in daisy chain?

I would be grateful for any comment.

Filip

Forum Post: RE: ADS130E08 Sample Code

J��rg Boge — Fri, 24 May 2013 09:14:00 GMT

Hello Tom,

I would like to get sample code too.

For witch processor is not important. To see witch registers has to be set and timing is important.

So it could be any c-source You have.

regards

Joerg

Forum Post: RE: ads1248 Basic Application

Horizon Telemetry — Fri, 24 May 2013 07:02:00 GMT

HI Joachim,

I will go with the series connection of the PT100s as you suggested earlier. See the revised schematic. At some stage I will need to measure a PT1000. I don’t think this will affect the basic setup.

Thanks for the calculator. I will do the calculations for the values next week and revert.

With regard to single ended inputs, I think using the LM7705 is the way to go for me now. Thanks for the info. Some sensors I will use are resistive and vary from 5K to 3M Ohms or 1K to 2K Ohms. To read these sensors do I apply the IDAC current or the Vbais voltage to the selected input? One input will be tied to 0V as you suggested.

I will work on the filters do and revert with queries if any.

Regards Tom

Forum Post: RE: LMP91000 circuit design?

Eyup Semsi Yilmaz — Fri, 24 May 2013 05:31:00 GMT

Thanks for attention!

Just i added prallel resistor to between sensor's pins.Now it is reacting whenever i execute the system:)

All configurations are same.

Forum Post: RE: ADS1293EVM Schematics

Bo Nystedt102116 — Fri, 24 May 2013 02:39:00 GMT

Hi Sergio

I have a project in which I will use ADS1293 and TM4C1233. Both devices use LDOs. TM4C1233 uses in the design I've seen TPS73633DRBT and the ADS1293 LP2XXXX-3.3NOP. When I read the two datasheets I see no reason why I can't save space by just let both devices get the their current from the very same LDO. If I am right, which one of the two LDOs should I choose?

Regards Bo

Forum Post: RE: defibrillator protection circuit

Bill Burris — Fri, 24 May 2013 00:30:00 GMT

Bill,

Attenuation occurs when the HV protection resistors on the ECG inputs create a voltage divider with the differential amplifier input impedance. Attenuation from defibrillation protection should not be a problem when using high input impedance amplifiers. For example if the protection resistors are 10Kohm and the input impedance is 100Mohm the ratio is 10K/100M or 1/10K. So there would only be 1/10,000th reduction in signal amplitude. Defibrillator protection also involves using TVS diodes or neon lamps for clamping. These components leak very little current but they do have capacitance to be aware of. The HV input resistors and the capacitance of the TVS diodes create a filter pole. Generally the capacitance is very low creating a high frequency pole and this is still not an issue when monitoring low frequency ECG. For example if the input resistors are 10Kohm and the TVS diodes are 500pF they would create a pole = 2Pi x R x C = 6.28 x 10K x 500pF = 0.000031415 S = 31,830Hz. This pole is high enough to not cause any attentuation of the ECG signal.

As far as MRI monitoring; The wires in the ECG leads will conduct dangerous levels of current into the patient and have to be removed before the MRI procedure. There has been research into ECG monitoring during MRI procedures with some success in the pacemaker and AICD industry. But at this time I do not know of any external ECG monitors that can be used during an MRI scan. So even if the WiFi radio worked, the monitor cannot be used during MRI procedures.

Bill Burris

Sotera Wireless

http://www.soterawireless.com

Forum Post: RE: ADS1258 crosstalk issue

Christopher Hall — Thu, 23 May 2013 18:45:00 GMT

Hi Alfred,

Do you have any data you can share with me? I would like to understand the magnitude of the errors you're seeing.

There are many things I could recommend trying in your circuit. I emphasized my biggest concerns below:

Short resistors R49 and R51 and see how this affects the results. Note that the MUX output has some parasitic capacitance associated with it; plus this capacitance is in parallel with the op amp input capacitance. These parasitics, plus the 10kOhm resistors are creating a second RC filter in your signal path.
Capacitors C13, C14, and C15 are connected in a "Y" configuration. Is this connection being used to try and mitigate the common-mode capacitor mismatching (I can recommend a different way to reduce common-mode capacitor mismatching)? The common connection where C13,C14, and C15 meet is a floating node, with no DC path to discharge. This node could be building up charge and causing errors. Perhaps you can short C14 and see if this helps?
Short resistors R17 and R27 and see if this helps. Your "V1" and "V2" inputs are referenced to ground, however, these resistors are only pulling AIN 11 and AIN15 down towards ground. Shorting these resistors would make a better ground connection.

Are you seeing issues with measuring "V2"?

This input is very similar to "V1". The main difference I see is that you are always measuring "V1" before "V2"; however, the meaurement preceeding "V1" always changes. I would expect you are having the biggest error in cycle 3.

Best regards,
Chris

Forum Post: RE: ads1299 and msp code?

Jaballi Maher — Thu, 23 May 2013 14:02:00 GMT

(Please visit the site to view this file)

Please Greg Hupp is that the installation of the ADS1299 is true for the acquisition of EEG signal? and how to convert the binary string (27 bytes " 3 byte and 8 channels") on the actual number of ADC24bit (SEGMA delta)?
thank you?

Forum Post: RE: Selecting ADC for my application

Jaballi Maher — Thu, 23 May 2013 11:46:00 GMT

when I receive data from the ADS1299 it is in binary form. So i think i should convert them on float in order to plot them on the screen ???

Forum Post: RE: ADS1299 interface with pc through MCP2210(usb-spi converter HIID)

Jaballi Maher — Thu, 23 May 2013 11:39:00 GMT

pavan shet

I am a student and I need urgently please a circuit very easy, only students with a GET ADS1299 (I have to use 8 among chanel) because I have to present the work in front of a jury commitee , please Pavan Shet is urgent because my future related to this work. please i need your help please

thank you in advance

Forum Post: RE: ads1299 evaluation module problem

Jaballi Maher — Thu, 23 May 2013 11:21:00 GMT

please how to convert the following binaie (27 byte "3 byte start and 24 bit of each string" (it has 8 channel)), ie the result after the conversion Delata SEGMA on 24bit for ADS1299 for real numbers?

Forum Post: RE: ADS1256 Voltage Reference

Damien Dusha — Thu, 23 May 2013 00:14:00 GMT

Thanks Chris, just the answer I needed.

-- Damien

Forum Post: RE: ADS8556 - Determine the proper R/C filter

Tom Hendrick — Thu, 23 May 2013 00:11:00 GMT

Hi Marc,

I've asked the author of that application note to get back to you regarding your questions. You should hear from him soon.

Forum Post: RE: LMP 90100 only the last register written can be read

Paul Jensen — Wed, 22 May 2013 20:59:00 GMT

Hi Murali,

Thanks for the response. The URA was the problem. I interpreted the documentation incorrectly, and I assumed that the R/WB for Transaction 1 identified if you were reading or writing the register, not the URA. So, when I wanted to read a register, I would set the INST1 byte to 0x90, which would read the current URA rather than set the new URA I was providing.

Everything works fine now; I can read and write all the registers.

Regards,
Paul

Forum Post: RE: Total Error for AD1115 using +/- 256mV FS setting

Bob Benjamin — Wed, 22 May 2013 20:27:00 GMT

Hi Mark,

The dominant error at the center of the graph is usually offset (but it could be linearity.) Offset error doesn't scale (nor does linearity), but this too can be calibrated out. The total offset error will depend on supply voltage used and whether you make the measurement differentially or single ended.

If you short the inputs, you can subtract (or add if the offset is negative) the correction value to make the result 0. This same factor would be used to adjust the subsequent readings.

Best regards,

Bob B

Forum Post: RE: ADS1298--DRDY always high

Javier D��az — Wed, 22 May 2013 16:47:00 GMT

Hi, I am working with the Ads1298 Evaluation Board controlled using the MSP-EXP430F5438 Experimenter Board and the systems works fine.

Now I have tried to migrate from the MSP-EXP430F5438 Experimenter Board to MSP-EXP340FR5739 Experimenter Board.

Initially, all works fine, but after 5 or 6 seconds the DRDY signal stops generating interruptions and remains constrantly Hi.

Any suggestions about what maybe happening?

Thanks in advance!

Forum Post: RE: ADS1299EEG-FE WINDOWS 7 COMPATIBILITY

Troy Thielen — Wed, 22 May 2013 14:25:00 GMT

YES

Forum Post: ADS1299 power consumption

Mohammad Behfar — Wed, 22 May 2013 09:58:00 GMT

Hello all forum members,

I need to know how power consumption of ADS1299 changes as a function of both Amp's gain and Data Rate.

I could not find any information about it in the datasheet. Can anyone provide me any information on that?!

Regards,

-Mohammad