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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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 ...
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1answer
38 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
52 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 ...
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1answer
39 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
37 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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44 views

Why does my 3-OpAmp Instrumentation Amplifier give me unexpected values?

I'm working on trying to boost the signal from some strain gauges attached to a very stiff impact arm. The idea is to see when the arm has impacted, and if it's still applying pressure. I figured I ...
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1answer
33 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
44 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 ...
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43 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, ...
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1answer
107 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
38 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 ...
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1answer
35 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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92 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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56 views

Increasing output voltage from an INA125p to Arduino?

I have a 780 gram load cell with a rated output of 0.8 ± 0.1 mV/V at rated load. I also have an INA125p instrumentation amplifier, which I am using with \$R_G\$ = 60 \$ \Omega\$ (gain = 1000). ...
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1answer
255 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, ...
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2answers
42 views

Decreasing ADC Reference vs. Amplifying signal

I have a sensor interfaced to ADC but the Range I am getting is not enough, so now there are 2 options, Gain up the signal or Reduce ADC Gain. But as I heard it, reducing ADC gain will cause more ...
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57 views

Design of Capacitive electrodes using Kicad

I am looking into building a capacitive electrode. I find a lot of research papers available online , however none that tell me how to actually construct the capacitive electrode. Most deal with ...
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1answer
88 views

filters for in-amp, difference amplifier, and non-inverting op amp

I am new to this matter and would like to learn how could I determine the right filters to use for my circuit. I have read some tutorials about active and passive filters but can't get the right ...
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1answer
154 views

Filtering Noise on Strain Gauge Circuit

I am making a digital weighing scale circuit and currently having difficulties understanding filters that are commonly used to reduce noise in these type of circuits. My load cell is a full-bridge ...
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2answers
121 views

Why does this analog front end EVM have 4 pins per channel, instead of 2?

Here is a photo of the ADS1299 EVM from texas instruments. It is an 8-channel low noise analog front end chip. I understand that for each channel, the potential difference between plus and minus are ...
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1answer
137 views

Instrumentation amplifier: resistor to ground for input bias current?

I've inherited an RF amplifier design (50MHz-1GHz) that uses an instrumentation amplifier to accept a DC voltage control signal. Neither myself nor my PI can explain why R8 and R18 are present. My ...
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2answers
123 views

AD620 in-amp reference pin

I have a weighing scale project using a 200kg load cell with a rated output of 1mV/V. I used 5V as excitation voltage and an Ad620 in-amp for my amplifier. I only need atleast the 0-100kg so I only ...
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1answer
60 views

MCP6N11 voltage reference and output problem

I am currently trying to setup an instrumentation amplifier and I used MCP6N11. Basically I'm just trying to test the instruamp to output a certain voltage gain before I connect it to my actual ...
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79 views

How to wire four half-brige 3-wire strain gauge load cell to an amplifier?

First of all, i am given a task to make a digital weight machine. For this i have chosen 4 strain gauge (3-wire load cell) which you can find here. I have searched all of the links i found on the ...
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1answer
159 views

using AD620 with load cell

I am currently using an AD620 to amplify the signal coming from my load cell. I am supplying it with single supply of 5V and 0V. Below is my preliminary circuit. I am feeding half the supply to the ...
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1answer
218 views

AD620 with load cell help!

I have bought a 200kg load cell and an AD620 in-amp. I only want to use 100kg as the maximum weight capacity. I want to power the load cell and the in-amp from the 5v pin of the arduino. The seller ...
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1answer
208 views

Why is my op-amp chopping up my signal?

I have built an instrumentation amplifier out of two op-amps in a quad op amp (MCP6L04T). The input signal is coming from a low-impedanece source (~17k) and most of the information in that signal is ...
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4answers
90 views

Using Differential Amplifier to reduce required RC values

I need to implement a low pass filter to convert a 20kHz square wave into a 20kHz sine wave. It would be nice to be able to use lower values, because in CMOS large resistors and capacitors take up ...
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1answer
67 views

Instrumentation (or diff) Amp saturating when measuring low voltage

I need to measure (amplify) a very low voltage, by low I mean in the order of 20 uV. Right now, using a lab multimeter, I am clearly and repeatably measuring the voltages so I thought that amplifying ...
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1answer
133 views

Current sensor with instrumentation amplifier (LT1167)

Objective I'm trying to make a current sensor that can accurately measure current up to 5A. In order to do this I'm using an instrumentation amplifier (LT1167) to measure the voltage difference ...
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232 views

Problem connecting INA114 with LM331 for voltage to frequency conversion

i'm actually using a load cell and i would like to send the load cell information to an android tablet through jack audio. Then load cell caracteristics are presented here: ...
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68 views

Lock-In amplifier

I am currently performing experiments on FM Atomic Spectroscopy. The light from VSCEL is interacting with an akali vapor in a cell and the output is received at the photodetector. The output contains ...
3
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1answer
452 views

Why is my instrumentation amplifier's output voltage completely wrong?

I'm trying to amplify the voltage of my load cell (Wheatstone bridge I believe), but my calculated values are not the same as my experimental values. The load cell outputs a differential voltage of ...
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70 views

3 wire load cell and ina125p

I'm making a digital weighing scale out of 3-wire load cell. I found in weighing scale which I bought. the load cell has got 3 wires black(B)-red(R)-white(W). the resistance b/w BR,RW and BW was ...
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2answers
236 views

AD620 voltage noise and ADC SNR calculation

I want to calculate theoretically my effective resolution from C8051F350 in-built sigma delta ADC with different interface options like ISL28134, ADA4528, ADA4898, OPA211, mcp6v07. I want to know ...
3
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3answers
178 views

Using step-up converter in metering instrument?

I am designing a pressure calibrator (my first Real project), which is supposed to measure from 0-200.00 mmWC (20000 counts) using Silabs C8051F350 (inbuilt 24-bit Sigma delta ADC). Sensor used is a ...
0
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1answer
185 views

Building instrumentation amplifier with resistors and op-amps

According to this question, it is possible to build instrumentation amplifier out of resistors and operational amplifiers. I am more interested in the version where the gain is set by changing Rgain ...
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1answer
60 views

Questions about the front end design of amplifier circuit

Question 1: Recently, i'm working on a design which needs to design an INA front end. The most used circuit like this (please omit the component values): You see, the two 10M resistors which ...
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1answer
158 views

What does the feedback capacitor do in Right-Leg-Driver?

It so happens I have seen some people mention about connect a feedback capacitor across the opamp for RLD would improve something better. Can someone capable to explain about the use of the ...
2
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2answers
384 views

Understanding load cell and instrumentation amplifier

I want to build a weight scale with 0.1 gram resolution. But I have some problems in my initial stage. I am using a load cell with sensitivity of 1mV/V and excitation voltage of 3 V. With no ...
0
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1answer
186 views

Load cell without In-amp

I have a 0-1kg load cell with 4 wires: Excitation + and -, and Signal + and -. I haven't had any problems wiring them up correctly without amplification, and my voltmeter shows me a 1 mV difference ...
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1answer
222 views

Reading a gas sensor with range from 0 to 60mV with an ADC

I need to take a reading using an ATmega328P of a gas sensor. The ATmega328p has a built in 10bit ADC giving only 1024 'steps' The data sheets for my O2 sensor are: ...
3
votes
4answers
249 views

Type-K Thermocouple interface problems

I'm trying to interface to a type-K thermocouple with an ATXMEGA128A4U and have been experiencing some difficulty and I'm hoping someone can confirm the process I am using. Details.. 1. TC is ...
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1answer
111 views

Instrumentation Amp problems

I have a 1000 times gain circuit using an INA826: Up to 2mV input 2V out, it works fine, after that point in only gets up to 2.7V. R? is a 6.2kΩ, that brings the 49.9 r to 49.5.
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2answers
354 views

How to hook up a load cell to an Instrumentation amplifier correctly

I am trying to get load cells connected to an instrumentation amplifier. The load-cells I have are extremely similar to the ones here https://www.sparkfun.com/products/10245. They have 3 wires coming ...
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2answers
204 views

Is the supply for a differential op amp compulsory?

Is the supply for a differential op amp compulsory or can we operate those without a supply? I just want to amplify the difference of inputs, I'm not in need of any supply voltage.
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3answers
384 views

How to set up an experiement to measure SNR for an EEG amplifier?

I have built an EEG amplifier with gain of 2000 and bandwith at 1~40Hz. I use an Instrument Amplifier for pre-Amp and a non-inverting opamp as post-amp and finally bandlimit at 40Hz using a 4th-order ...
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0answers
83 views

Design an Instrumentation amplifier

I have design an Instrumentation amplifier for a very high sensitivity Load cell. What factors should i consider in selecting the right opamp, resistor values for the In amp. I know that it is ...
0
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2answers
134 views

Differential Pressure sensing circuit

I'm trying to understand a differential pressure sensing circuit that I have. Have attached rough design sketch as well. Sensor used is "10 INCH-D1-MV-MINI" by Allsensors. Output span is 20mV for 10" ...
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1answer
848 views

Voltage ramp in INA125 output

I am using a INA125P to amplify the signal from a beam load cell - and I have noticed a frequent ramp in my INA125P output signal, of about 100mV every 200uS. EDIT: My gain is roughly 800x. I have ...