An instrumentation amplifier (InAmp) is an integrated circuit or operational amplifier topology that has high input impedance differential inputs and a low impedance single-sided output. Because of precision laser-trimming techniques for passive circuit elements, InAmps implemented as integrated ...

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56 views

Understanding an opamp circuit

I'm trying to learn more about analog circuits but i'm currently getting stuck at an opamp circuit which amplifies signals in the range of 0-512~ uV. According to the schematics below the maximum ...
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2answers
81 views

Twisted pair for long distance voltage measurement

I want to measure the voltage drop across a shunt, but the ADC performing the measurement will be far from the actual shunt - perhaps five meters. I'll need to measure voltage drops across the shunt ...
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20 views

Post amplification filtering

I'm trying to construct a guitar cabinet, and currently have an odd setup. Here's a visual: http://postimg.org/image/g6nl0zuq9/ The circuit is: Amplifier(+)->S1 S1->S2->S4->Amplifier(-) ...
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69 views

Battery monitor for a camper van electrical system

As one of my first DIY projects, I'm going to build a battery monitor for the DC battery/solar/inverter system in my camper van. The van has 440 Ah of lead acid batteries and DC currents up to 200A ...
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82 views

Confusion around common mode voltage

I understand the basics behind the concept of common mode voltage and CMRR and friends, in the context of differential amplification. What I don't understand is the determining if the whole concept ...
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44 views

Monitoring a large array of load cells

I have a large array of 8x8 load cells I'd like to monitor, and I'm looking for an efficient way to do that. Obviously, one option is 64 independent instrumentation amplifiers, but that's expensive ...
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42 views

Is Input Offset Voltage perfectly proportional to output

Is Input Offset Voltage perfectly proportional to output in an opamp? Such that if one where to enter 0V differential to the +V and -V inputs, the output would be A*Input_Offset_V. Also, when using ...
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46 views

LTSpice Instrumentation amplifier simulation output

I am using an LTSpice model for an instrumentation amplifier (AD8222) to learn how to simulate things in LTSpice. My output is not what I expected. My model is based on this description: ...
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25 views

Programmable gain instrumentation amplifier with R-2R ladder and analog multiplexer

I want to build a programmable gain instrumentation amplifier with power of two possible gains (1x, 2x, 4x, 8x...). Is there a way to use a R-2R resistor ladder and an analog multiplexer in order to ...
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36 views

EMG circuit reference electrode voltage

I am planning to implement a circuit for analysing and processing EMG signal. Prior starting any of the implementation I did some research about existing circuits. Most of the circuits make use of two ...
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2answers
101 views

Rectification of Micro DC voltage levels?

I am building a payload for a high-altitude Balloon launch in the club I started which will be measuring DC voltages (electric field) at different altitudes using a wire dipole or two metal plate ...
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1answer
34 views

Digital GND of PGA204

I'm using TI's PGA chip PGA204. It has a DGND and an AGND. And it states: Digital ground can be connected to any potential from the V– power supply to 4V less than V+. Digital ground is normally ...
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112 views

A DC micro-voltmeter

Basically I will be calibrating circuits to a high degree of precision. Keeping it minimalistic, I figure all I needed for that are resistor networks, voltmeters and a few high precision voltage ...
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88 views

current sense circuit - High side sensing/Low side sensing

I want to measure the current through the 2 ohm Load resistor.I have read about high side and low side sensing.But I am confused about which method should I use in my case as the FETs are part of ...
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2answers
76 views

Difference amplifier

I am simulating a difference amplifier circuit using LT1215 Opamp. I'm using LT1215 since I need supply voltage around 3V. The input voltage for both the terminals of the opamp is 200 μV and 100 μV. ...
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1answer
55 views

pH sensor, is the cebo-lc device suitable?

I would like to interface a pH probe. I know there are various threads on this topic. If found this two most interesting: Miceuz suggests two suitable instrumentation amplifiers (INA 116 and AD549). ...
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59 views

ECG cardiac monitoring [closed]

How is the signal observed from electrode and electrode impedance is affected if we clean one of the pair of Ag/AgCl cardiac electrode by scraping it with steel wool until it was shiny and bright
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36 views

Charged Pickups

I was building a 9v based Fuzz Face circuit at home. I didn't have the correct value capacitors but I decided to give it a go anyways using values that were MUCH below the schematics values. After ...
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2answers
123 views

Multimeter circuit review

I'm designing a very simple multimeter circuit of which the ADC is that of an Arduino Due. Could you have a look at the circuit and tell me what could go wrong, what could be improved etc.? ...
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1answer
48 views

Digital potentiometer as INA129 gain

I'm working on a waveform generator for which I'm using the DDS AD9833 chip to generate sine signals and triangular signals. I'm trying to amplify these waves since the AD9833 output is 600mVpp and I ...
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3answers
88 views

INA125 single supply small weight problems

TL;DR My wheatstone bridge won't respond to small weight changes when using single supply. I'm trying to wire up this circuit below using these 5kg load cells. I am able to get the circuit working ...
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2answers
81 views

ADC noise measurements gives bimodal (double hump) distribution in output values

I have designed a current measurement circuit which measures voltage across a shunt resistor. The voltage is basically measured with an instrumentation amplifier and the ouput its connected to the ...
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1answer
64 views

Instrumentation Amplifier output mysteriously increases upon connecting across a resistor, compared to connecting the same voltage directly across it

I am designing a simple resistance measurement circuit. Resistance range is from \$10m\Omega\$ to \$10k\Omega\$ and desired accuracy is 0.1%. The circuit provides constant current to the resistance ...
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4answers
184 views

Current sensing over a wide range

My project aims to measure the current of a photovoltaic module after applying a certain voltage across it. That means applying a voltage from 0V to 38 V with 0.1V step and measure the corresponding ...
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2answers
73 views

Issues with OpAmp gain and instrumentation amplifier (Packaged and designed)

simulate this circuit – Schematic created using CircuitLab Currently I have the following configuration using the LM358 single rail supply OpAmp. Each individual resistor value has been ...
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49 views

Why common mode voltage can damage device?

As title mentioned, why too large common mode voltage can damage a device? Especially an instrument amplifier?
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126 views

Auto Zero Circuit on AD625 datasheet

The datasheet for the AD625 instrumentation amplifier shows an example circuit with 'Auto Zero' (Figure 36), below. In this circuit an op-amp AD711 is being used to give an offset voltage to zero the ...
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1answer
66 views

What is the best method to compensating offset at the output of a peak detector circuit?

Brief of Application: The signal conditioning circuit developed is used to detect or capture the peak values of dynamic systems such as the impulse tools. In this application, we use an impulse tool ...
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39 views

AD8237 Output Offset Issue

I'm building an EMG circuit and have chosen to use the AD8237 as my front end amplifier. It's setup as below: R20 is actually a digital POT so I can change the gain. The amp is setup with a gain ...
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1answer
123 views

Homemade PC EKG circuit

About a week ago I had an idea to build a computer EKG using the computer's mic input as a signal input. One of the most complete tutorials I found on the internet was this one (that is applicable on ...
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1answer
153 views

How to use an instrumentation amp?

I have a two-wire Pt100 element and a 5V ADC and want to measure the temperature. I have made a wheatstone bridge like below and connected it to an instrumentation amp. No matter the resistance of the ...
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2answers
98 views

Resistor values for getting a gain of 10.86 in instrumentation amplifier

I am just stuck with a problem. Here using an instrumentation circuit (see image below). I want to know the exact value of resistors for a gain of 10.86. I have calculated and found some values (25K ...
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1answer
78 views

Understanding input voltage noise of AD8232

AD8232 has a built-in instrumentation amplifier with a fixed gain of 100. I am interested in using this device for amplifying EEG signals. Page 3 of the linked datasheet describes input voltage noise ...
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1answer
100 views

Differences between preamplifier, instrumentation amplifier and LNA

I am confused about the definitions of these amplifiers. It seems LNA is used for RF frequency band but I also see people using INA's for receiver. Why LNA's need careful impedance matching but INAs ...
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157 views

Strain Gauge and Arduino

I have these 2 strain gauges as you can see in the image (code 632-180) and I want to connect it to the Arduino so I can read the deformation. They should be in Wheatstone Half Bridge. I read that ...
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1answer
71 views

Instrumentation Amps for AC signal measurement

I am trying to measure excess resistance fluctuations in resistors. The circuit itself is very simple. Its a wheatstone bridge excited by a AC drive. the idea is that this drive will modulate the ...
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1answer
433 views

LM324 Difference / Instrmentation Amp 1mV Signals

I need to amplify 1mV signal from a wheatstone bridge (no DS available). 5kg max weight; output is 1mV/Kg @ 5V. The resistances are 880+880 and 749+749. Currently I only have LM324 and LM358. And ...
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0answers
109 views

How to amplify a signal containing square pulses at milivolts to a couple volts

I was on it for a time. I'm planning to generate a signal containing square pulses from a smart phone's audio output. As I can get any shape of audio signal from smartphone's audio output, I want to ...
2
votes
1answer
98 views

AD8222 single supply EMG

I am working with the AD8222 dual package instrumentation amplifier from Analog Devices. I want to build a compact EMG system so I am trying to use this chip since there are not a lot of dual IAs on ...
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1answer
68 views

Sampling many low voltage analog signals

I'm trying to sample 128 low voltage (a few millivolts) analog signals at around 800 samples/second. My original idea was to hook up 128 instrumentation amplifiers to 128 ADCs, but that turned out to ...
1
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1answer
60 views

In-amp output clamps to reference voltage

I am using AD8231 instrumentation amplifier in unity gain configuration. I used the inbuilt op-amp to provide reference voltage as the datasheet suggests. A 4.4kHz sine wave generated with my ...
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1answer
85 views

Single input instrumentation amplifier

I have an instrumentation amplifier, INA 126. I am using it to amplify the physiological signals from the eye movement. The circuit I have constructed has 2 stages: 1st stage has INA 126 with a gain ...
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1answer
120 views

Unstable voltage output for strain gauge application

I am doing a half bridge strain gauge application and it is connect to INA125P and with gain about 185 with Rg 330 ohm.below is my theoretical circuit diagram, my circuit is base on this picture to ...
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1answer
129 views

How Simulate Right Leg Driver

I am having trouble simulating Right Leg Driver in an amplifying circuit of eeg signals. The schematic of the circuit: The instrumental amplifier circuit has a gain of about 2 and E1 have 10m ...
1
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1answer
94 views

Different weights on different temperatures - load cells and ad620

I have a set of load cells connected to a AD620. Everything is working good except when I change the temperature. The temperature can vary between -10 and 50. I have the AD620 connected to an MCP3208, ...
2
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1answer
168 views

power supply oscillates when loaded with instrumentation amp

I've been working on an instrumentation amplifier for a PWL ECG signal in LTSPICE. It should be able to filter out the common mode noise. I Also need to design a power supply. Both the power supply ...
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1answer
202 views

How to calculate the gain for a load cell to be used with instrumentation amp?

I was hoping someone can give me a step by step process for calculating the gain of my load cell.Here is the datasheet to it LoadCell datasheet. I also plan on using the INA125p instrumentation ...
0
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1answer
47 views

how to setup a ph sensor probe

I have a INA126 IN-Amp. I hope to use it with a ph probe. But I am not sure exactly how to do that. should I put the probe in series with a branch of a resistive wheat stone bridge, or just tie it to ...
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2answers
358 views

EMG design help using AD8221 INAMP

I'm designing active electrodes for surface EMG, active electrodes being electrodes directly connected to a pre-amp and filtering stage on the measurement site. Im working with the AD8221 IN-AMP to ...
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1answer
756 views

Connecting a (small) load cell to Arduino using INA125P

I want to connect the load cell of my (micro) scale to my Arduino. The scale itself is able to weigh max. 800 grams with an accuracy of 0.1 grams - what I want to weigh are loads up to max. 100 grams, ...