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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Operational amplifier parameters: Input bias current, Input offset current, input offset voltage

I've been reading about input offset voltage, bias current, and current offset for a few days now and still can't get some things straight. I'll summarize what I understand and then pose the ...
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29 views

Instrumentation Amplifier REF pin maximum voltage

I'm a spanish engineer student doing my end-of-degree project. I need to remove the offset of a strain gauges bridge and i'm trying to make the calibration automatic, using a DAC (digital to analog ...
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4answers
58 views

Is there a special symbol for instrumentation amplifier, to distinguish it from an opamp?

Is there a special symbol for instrumentation amplifier, to distinguish it from an opamp? If I use the opamp symbol in a circuit diagram, it looks wrong, like it's missing components:
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30 views

How to work out (Hfe) AC Forward current transfer ratio for ZTX650 BJT Transistor?

Please can someone suggest to me how to work out the AC Forward current transfer ratio for this BJT Transistor (ZTX650 BJT Transistor) used in common emitter. I looked on the data sheet (herewith is ...
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104 views

Difference between HX711 and INA125?

What are exactly the difference between these two amplifiers and why is it that HX711 would be better to use than the INA125 with arduino?
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1answer
1k views

gain with no side effects

I want to see a signal (5-25 microvolts | 1-35HZ) on my computer.but I dont know electronics so I just have one question: I need to amplify THE signal to reach ...
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1answer
84 views

Why there are minimum three electrodes used in ECG, EMG measurements?

My question is related to the number of electrodes used in ECG/EMG kind of signals. I know that voltage measurement is a potential difference measurement. I understand the concept of signal and ...
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2answers
75 views

Instrumentation amplifier with frequency-dependent gain?

I have an AD8421 (instrumentation amplifier); it has two pins to connect a resistor Rg that sets the gain --- G = 1 + 9.9k / Rg. For example, a 100 ohms resistor produces a gain G = 1 + (9900 ohms / ...
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50 views

arduino control positive and negative voltage

I need an Arduino to control a low current (<10 mA) voltage output that can sweep from about -4 V to + 4V. I'd like to avoid using PWM because of AC noise, I can use MCP4725 Breakout Board - 12-Bit ...
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0answers
56 views

Measuring battery voltage fluctuations and spikes in an analog wall mounted clock when the second hand ticks

As the title suggests, my goal is to be able to pickup minute voltage fluctuations of an AA battery cell of the wall-mounted clock, each time the second hand ticks. My first intuition would be to ...
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1answer
252 views

AD620 in Proteus: timestep too small

I've made this circuit in Proteus, as a part of a practice report: In real life it works, as I built and tested it. But in Proteus, when I want to run the simulation, I get these errors: ...
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1answer
262 views

Understanding the guarding circuit in an instrumentation amplifier

I've got a project to make but I have trouble understanding what is actually going on. In circuit below, I have to calculate the resistor values, choose op-amps and explain how the whole thing works. ...
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3answers
763 views

Single wire USB

I wanted to convert a USB differential signal into one signal, and then send it over one wire, and then restore in back to differential signals at the other end. I wanted to do this for a USB 1.1 ...
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1answer
46 views

DC LVDT Excitation voltage to NI CompactDAQ

I am currently working on getting reading from an LVDT for a project the present model is the DC LVDT model Omega LD620-25 As per it's datasheet the model requires an excitation voltage of 10-30V and ...
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1answer
59 views

Advantage of using “IF Amplifier” over traditional OP amp?

I am trying to receive 1MHz ultrasonic signal with transducer. So, I will need to design some kind of filter to only pass 1MHz signal and filter out other noise signals. Searching online for OP amp ...
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1answer
72 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
106 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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2answers
176 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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3answers
101 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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1answer
77 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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2answers
53 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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1answer
173 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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2answers
83 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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3answers
136 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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1answer
183 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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2answers
92 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
63 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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1answer
69 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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2answers
163 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
63 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
239 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
105 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
83 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
213 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
122 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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1answer
55 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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169 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
87 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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1answer
59 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
162 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
209 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
104 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
96 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
135 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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1answer
182 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
85 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 ...
2
votes
1answer
729 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
145 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
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1answer
120 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 ...