116 Threads found on edaboard.com: Adc Negative Input
I think the testing depends on the resolution of the adc you designed.
If the Spec is lower than some DAC in the market. you can buy one and design a test board by yourself. it is not necessary to have a high performance instrument.
Analog IC Design and Layout :: 28.12.2004 10:41 :: piao :: Replies: 8 :: Views: 868
There is always a chance of blowing a chip with to high or negative voltages applied to its inputs. Some 5V IC can withstand a couple of more volts and a small (between 0 and -1V) negative voltage, but if you use a small serial resistor (100Ω) and a 5.1V zener diode connected between adc input and GND (...)
Microcontrollers :: 19.08.2005 23:26 :: IanP :: Replies: 4 :: Views: 2650
I'm trying to get samples from output of a sensor.
Output varies between 1.1V to 3.8V.
My adc (it's a 16bit adc sampling at ~80Ksps ) has only positive external reference (VREF) input.
I used an external tempereature compensated precision 4.096V voltage reference.
Now it is sampling 0 to 4.096V . But my signal is only at 1.1 to (...)
Analog Circuit Design :: 17.05.2006 03:50 :: Sobakava :: Replies: 1 :: Views: 1021
That is a very common issue since adcs are usually unipolar. Time ago I saw at Maxim website a simple but effective 3 Rs front-end solution which address your problem: adc input connected to a voltage divider from Vcc (2 Rs) and another R from there to your input (negative sometimes) choosing proper R values (...)
Microcontrollers :: 24.07.2006 08:32 :: turttle :: Replies: 5 :: Views: 4257
Dear all :
as the attachment shown, the reference voltage generator ( for Pipelined adc
testing PC Board) is implemented by two resistors, two capacitors, and two unit
My questions are as follows:
1. What's the purpose to add two 10Kohm resistors in series in the positive input
node of OPamp ? since there
Analog Circuit Design :: 15.05.2007 14:59 :: AOQ :: Replies: 0 :: Views: 1011
please post your adc IC number so that we can have an idea on what you are actually talking about....
Analog Circuit Design :: 19.08.2007 11:45 :: A.Anand Srinivasan :: Replies: 4 :: Views: 1182
can anyone teach me how to convert 4 to 20mA input to digital output using PIC adc??i need settle this project within 3days but i dun have any experince with PIC...
Microcontrollers :: 16.12.2007 20:31 :: desertkids :: Replies: 6 :: Views: 1149
want to design 12 bit pipeline adc
can any one help me?
Analog IC Design and Layout :: 23.05.2008 19:56 :: ramaro :: Replies: 3 :: Views: 716
Hi Everybody ,
I have this adc code below , the ADRESH send to the pc stable and just great , while the ADRESL has lot of noises where i dont know from where i get them , can anybody help me out to sort this problem , i connected resistor and RC filer at the input of the AN1; which is not helping , i'm using 20MHZ pic18f , from where this nois
Microcontrollers :: 28.05.2008 05:13 :: engineer123 :: Replies: 2 :: Views: 707
in calculating the offset error of bipolar adc,whwther we need to take the first transission at the negative input or the deviation at the code zero
Analog Circuit Design :: 20.10.2008 06:00 :: prejaan :: Replies: 0 :: Views: 1574
Use an opamp and shif the voltage from -2V/+2V to 0V/4V by adding +2V offset, then it can be easily connected to the adc0808 ..
Here are details on how it can be done:
Microcontrollers :: 26.03.2010 21:00 :: IanP :: Replies: 3 :: Views: 718
I'm new in avr programming, and here is my problem:
I would like to sample a dc source who varies from 0V to 15 Volts, and we know that the adc of most mcu don't accept a voltage higher than 5V. The question is how to interface this voltage to my ATmega16.
Second problem: Is it possible to isolate this dc source from the mcu lik
Microcontrollers :: 30.01.2011 17:09 :: yokohama :: Replies: 14 :: Views: 2706
Hi, I need to sample an analog AC signal ranging between -0.1V to 0.1V. I will take the digital ouput to an fpga, however Im having diffuculties in choosing the right adc, since nearly all of the ones I looked act as if they accept only positive voltages in single ended operation and choosing a negative input to V- in differential (...)
Digital Signal Processing :: 24.01.2012 02:59 :: kutangurel :: Replies: 1 :: Views: 684
You need to calculate the resistor ratios for correct gain and care for keeping the AD8138 permissible input voltage range. VCOM is solely commanded by the required adc common mode voltage.
Analog Circuit Design :: 18.02.2012 18:44 :: FvM :: Replies: 3 :: Views: 384
One way to do it is to use an OP-amp connected as a summing amplifier and add some offset to get the output voltage for the zero point in the middle of the adc range.
Microcontrollers :: 11.03.2012 07:47 :: skogsjanne :: Replies: 1 :: Views: 706
There are well understandable reasons why a 100 MBPS adc should use differential inputs. A number of recent adc can be nevertheless used single ended with 0 - 3 V input range. A certain linearity reduction compared to fully differential input drive must be tolerated.
A fully differential amplifier gives (...)
Digital Signal Processing :: 31.07.2012 04:12 :: FvM :: Replies: 20 :: Views: 748
Isn't the PIC adc a capacitive type?
If so it'll accept negative inputs to the adc and you will have to tell (program) the adc that you want bipolar input.
Professional Hardware and Electronics Design :: 11.01.2003 09:27 :: RegUser_2 :: Replies: 7 :: Views: 2075
I have a current transformer, and I whant to read the value using the adc of a 16F873.
Problem is, for 20A in primary, I get 20mA on secondary, an with a resistor of 100Ohm I get a sine wave of 2.828 peak.
I have tinked to put a rectifier bridge of schottky diodes, but any way, when I get 1mA, the voltage are all droped on diode
Professional Hardware and Electronics Design :: 09.03.2003 15:42 :: neuralc :: Replies: 5 :: Views: 2454
Searching for a 1-bit DAC schematic to use in the design of a swtiched capacitor SIGMA-DELTA adc. I know that a 1-bit DAC DAC is simply a switch that connects the negative input of the difference amplifier to a positive or a negative reference voltage. I just need a point in the right direction.
Cheers for any help :)
Analog Circuit Design :: 28.05.2004 08:27 :: cjupiter :: Replies: 7 :: Views: 4823
My question are:
1.) Is there an adc that can accept an analog input of -4.5V to +4.5V.
2.) What is that adc.
3.) Is it possible for the PIC16F877A to accept those values?
Microcontrollers :: 13.12.2004 10:18 :: glenjoy :: Replies: 13 :: Views: 6268
I want to make a circuit using TCL1541 adc Converter, and i dont know how protect it of high voltage or short circuit, anything.
Thank for your cooperation
Electronic Elementary Questions :: 23.01.2005 21:41 :: terka :: Replies: 4 :: Views: 4323
I going to use adc in my digital oscilloscope project but i confuse about the input of adc. Actually how much the voltage that i can measure, i mean the voltage can enter the adc. I knew something like Vref = -5v to +5v. But if i want to measure 100v signal, how can i make it? My adc specification is (...)
Digital Signal Processing :: 15.12.2005 12:09 :: shteo83 :: Replies: 3 :: Views: 812
The input may be positive or negative. Is possible to convert this kind of voltage to digital by PIC16F87x?
as I know, bi-polar input adc can do this. but PIC16F87x hasn't bi-polar input adc.
Microcontrollers :: 09.03.2006 18:24 :: Saboy :: Replies: 3 :: Views: 932
i am designing a temperature measuring project in which i am using j ,k,r,s,e, t type thermocouples. j ,k,r,s provide me 0- 5 volts (after opamp stage), but e and t type thermocouples provide me negative voltage (when they measure from -200C to 0 Celcisus). if i amplify i ll get a negative value .then how will i feed this to adc.wht (...)
Analog Circuit Design :: 09.05.2006 05:52 :: shaz :: Replies: 3 :: Views: 1696
Simplest - put resistive voltage divider with one side connected to stable voltage source second to your negative voltage output and middle to adc input directly or thorugh buffer .
Choose division factor to based on min negative voltage and voltage source resistors connected to .
Electronic Elementary Questions :: 12.08.2006 12:07 :: artem :: Replies: 7 :: Views: 1169
I'm assuming that you're testing a real adc. If you're still simulating it some of the questions below are not applicable:
-What is the resolution of the adc?
-What is the number of points in the FFT? You should use something above 2^14... I would advise 2^16.
-Is the yy-axis the signal power in dB ? If yes, how come there are negative (...)
Analog IC Design and Layout :: 20.03.2007 04:22 :: maxwellequ :: Replies: 4 :: Views: 814
You must be very carefull. Your need a step down transformer (a 220VAC/5VAC), but also you need to avoid any negative voltage in your adc input.
Please refer to:
Measurement Systems: Application and Design
Analog Circuit Design :: 21.06.2007 10:02 :: ronyutp :: Replies: 14 :: Views: 2136
Hi can you give some partnumber for bipolar adc's thanks
Electronic Elementary Questions :: 22.06.2007 04:05 :: roy mathew :: Replies: 5 :: Views: 670
I have a need to read the negative voltage . If there are any suggestions.
Please give me ideas .
Can adc read the negative voltage ?
Very very thanks ~
Microcontrollers :: 16.11.2007 07:40 :: TERRYWU3 :: Replies: 6 :: Views: 2749
Hi every one .
Can anyone help me how to design 4-20mA input (output of pressure sensor) to give me 0-5v output for adc.Because i want to read it in microcontroller.
Added after 1 hours 14 minutes:
I Need conditioning circuit using Op-Amp for this 4-20mA input to give 0-5v output f
Analog Circuit Design :: 02.01.2008 02:32 :: xenon2000 :: Replies: 1 :: Views: 1196
I have an adc LTC2410. How can it measure negative voltage with respect to ground, but not IN-?
IN- will be grounded in measuring.
Hobby Circuits and Small Projects Problems :: 24.07.2008 11:14 :: funghome :: Replies: 3 :: Views: 6500
You can try to bias the input of the adc right in the middle of its range and then couple the audio signal through a capacitor. All you need then is make sure the cap is large enough for the lowest frequency and also make sure the signal does not exceed the range of the A/D, that is, the peak to peak amplitude of the signal must be less than the r
Hobby Circuits and Small Projects Problems :: 02.11.2008 10:32 :: VVV :: Replies: 2 :: Views: 3291
I have a delta sigma adc (cs5532). I'm trying to convert the small signals i.e mVs into digital. It has a 5V supply and a 2.5V ref voltage which is at 2.490 or 2.495V and maintained by a low ppm low noise ref voltage ic. The adc is in unipolar mode. So the negative values should be measured as zero and that is the case mostly. I'm getting (...)
Professional Hardware and Electronics Design :: 22.12.2008 11:27 :: seyyah :: Replies: 1 :: Views: 1608
Yes, its possible.
But this would lower down the 8-bit resolution. You leave ref/2 pin open, don't connect it. If I remember that PIN number correctly, in this you get range from 0-5V.You first takes the absolute value of -5V to +5V, so altogether difference of 10V, means if you give negative voltage, it must be get convert into positive value, if
Microcontrollers :: 26.12.2008 16:09 :: umery2k75 :: Replies: 5 :: Views: 2392
I am relatively new to 16 bits.
My task is to sample an analog ECG signal from an ECG amplifier (0-3v analog). I am able to display the positive values of adc on LCD, but unable to adc/sample the negative going signals. Can anybody point me to sample code for sampling negative going signals.
I am using (...)
Other Design :: 24.02.2009 03:39 :: Vinod Mehra :: Replies: 1 :: Views: 1997
I am a student currently working on building a hybrid racecar for Rensselaer Polytechnic Institute. According to the rules, the high voltage circuit must be electrically isolated from the control circuit. We need to measure the battery voltage, and I was thinking of using the popular ISO124 isolation amplifier. This is powered from both s
Analog Circuit Design :: 12.03.2009 02:05 :: se00an :: Replies: 0 :: Views: 1587
will it be ok to to allow more then +/-5 volt to appear on the Port A of PIC series microcontroller
or i should scale down the voltages before reading them
i am keeping in the mind that there is built in diode protection for negative voltages and the more then 5 volt positive voltages
thats why i have not included external diode to c
Microcontrollers :: 24.06.2009 14:20 :: malik_123 :: Replies: 3 :: Views: 1201
Hi dear all friends,
i had designed an adc that had Only Vin and Vref as inputs. both of Vin and Vref were between 0V and 1V:
Vin=0.5+0.5*sin(ωt) & Vref=1
Now i have to use of fully differential inputs (Vin+, Vin- and Vref+, Vref-).
now i mixed up for determining values of Vref+ and Vref-.
in fully differential scheme we (...)
Analog Circuit Design :: 14.07.2009 16:19 :: Monady :: Replies: 6 :: Views: 1270
1.4 V is full scale input of my adc.
Your dBFS value = 20*log(voltage/dbFS-voltage) ,
i.e. below 1.4V always negative:
voltage dBFS value
1.3V -0.64 dbFS
1.2V -1.34 dbFS
0.7V -6.02 dbFS
140mV -20 dBFS
100mV -22.9 dBFS
Analog IC Design and Layout :: 11.11.2009 10:21 :: erikl :: Replies: 1 :: Views: 1640
Hello, I need a pcb design for a microcontroller (89c51) which is interfaced to a keypad, LCD and adc804 whose input is connected to an adder ckt to taken in the negative voltages.. Some one plz do help me cause i am really new to all this ..:)
PCB Routing Schematic Layout software and Simulation :: 13.12.2009 20:24 :: kamekaze :: Replies: 1 :: Views: 2017
I am doing a microcontroller (89c51) based project and the peripherals used are adc804, LCD and a keypad. The input to the adc is both negative and positive voltage so does anyone know how can u make adc read a negative voltage. Some of my friends told me that i can add an (...)
Microcontrollers :: 20.12.2009 20:58 :: kamekaze :: Replies: 1 :: Views: 757
Hi guys ,
i need to amplify a shunt that give 1 mV per 1 Amp . I will measure from 0 to 50 Amp so 0 to 50mV. i want to amplify it to be 0 to 2.0 V for my adc input . Up to now i tried an instrument amplifier made of 3 OP270 . My problem right now is the low value 0 to 5 mV , i can't get precise stable measurement !! any idea ???
Analog Circuit Design :: 21.12.2009 07:09 :: mindstorm88 :: Replies: 13 :: Views: 2981
I'm trying to build an EEG using an ADS1298. This chip was built more for ECG than EEG and is a little too noisy to directly take an EEG signal with, so I'm trying to add some initial gain to get a better noise figure. My question is what is the best way to do this? This is a 24-bit A/D converter and I absolutely want the least noise possible.
Analog Circuit Design :: 30.06.2010 20:08 :: jlenoach :: Replies: 1 :: Views: 1529
New to the forum and it seems I have some question regarding using an op-amp to present a real word input to a differential adc.
I'll present some information of the time of input I want to be sampling. The input comes from a detector which has negative going pulses with rise times from 20-40 (...)
Analog Circuit Design :: 12.12.2010 23:28 :: hanua :: Replies: 3 :: Views: 636
Pls use differential input adc.
Analog IC Design and Layout :: 05.02.2011 03:53 :: leo_o2 :: Replies: 5 :: Views: 840
I have a Problem related to Fully Differential Pipelined adc Implementation. I have Problem in MDAC Section Only.
I have chosen SC MDAC topology to implement 1.5 bit MDAC.(Plz see attachment named "differential MDAC from Paper" attached)
I have big doubt while implementing MDAC differentially....
FOR SIMPLICITY I AM ONLY APPLY
Analog IC Design and Layout :: 23.03.2011 02:48 :: raditsme :: Replies: 0 :: Views: 1295
i am working on a sigma delta adc second order three bit and i do the schematic design on cadence and i get 100 db and it is ok when i make the layout and make post layout it become 93db i found in the drawing of fft a pulse at another frequency 200hz(my input frequency is 100hz and band width is 200)
and this is the picture
Analog Circuit Design :: 02.07.2011 11:03 :: hoka_89 :: Replies: 1 :: Views: 453
I need to measure 60V from battery (total 8 channels) and display the result in the LCD.
when i add protection diodes at the adc input i am continuously reading ZEROS.
I am able to read correct values with out the protection diodes (circuit reference R9, SD1 and SD2).
I have attached the schematic.
Somebody please suggest me what
Analog Circuit Design :: 13.09.2011 02:21 :: yviswanathbe :: Replies: 8 :: Views: 843
i am working on circuit to measure a negative voltage with a adc which will read only positive voltage(PIC MCU).i have a problem the positive of negative supply and negative of positive supply, both are grounded so clamping circuit will not work (in my observation).can anybody suggest any remedy for this problem .i want to (...)
Analog Circuit Design :: 14.09.2011 08:00 :: zeroskj1988 :: Replies: 1 :: Views: 364
If the allowable voltage is +5V for the adc then you may use a voltage divider to bring down the 0 - 10 V to a suitable level like 0 - 5 or 0 - 4.5V as per requirements. If 8 bit resolution is insufficient then you may go for a 10 bit or 12 bit adc.
Microcontrollers :: 09.12.2011 11:56 :: ark5230 :: Replies: 14 :: Views: 866