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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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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70 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
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4answers
133 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
71 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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42 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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135 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
212 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
55 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 ...
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2answers
44 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
115 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 ...
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2answers
378 views

Problem of noise with load cell and INA125P + Arduino Uno

I am here with a problem that I cannot solve. Here is the facts : I have a load cell : http://www.robotshop.com/en/micro-load-cell-50-kg.html that I want to use in both direction, so from -30kg to ...
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1answer
85 views

Instrumentation amplifier for load cells

In the most part of tutorials I see they use INA125 as the instrumentation amplifier for load cells. Is it ok to use another cheaper amplifier as the AD8237? Or is there a specification or ...
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1answer
485 views

3 wire load sensor connection to INA125P

I am trying to use a 3 wire load sensor, connect it to INA125 for voltage amplification and then use the amplified output to be fed to ADC of Arduino. I had used below configuration with INA125. ...
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2answers
252 views

Sensing weight with strain gauge, InAmp, ADC & Pi

I have an SEN-10245 sensor for weighing objects (essentially a strain gauge). The goal is to capture data with a Raspberry Pi, so the signal from the weight sensor needs to be amplified and then ran ...
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1answer
690 views

Hacking a four load sensor based personal weighing scale

I am trying to hack a personal weighing scale.I had taken help of this tutorial but the language used in this is not very easy to understand due to the non-standard naming used for load sensor wires, ...
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2answers
109 views

Determining correct requirements of Instrumentation Amp in measuring large current shunt

I'm trying to plan out a project of measuring large currents from my car battery through a shunt, and specifically I need help with the INA. I bought this Deltec 250 amp shunt from eBay, that looks ...
2
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1answer
216 views

Is it a good idea to make one instrumentation amplifier with three operational amplifiers for thermistor sensing circuits?

Is it a good idea to have those three amplifiers with LM741 Operational amplifier? Has anyone done this so far? I thought of this as this was a cheapest idea. The instrumentation amplifier costs about ...
3
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1answer
112 views

Amplification circuit for a limited range of output signals

I have a sensor that puts out a signal between 0 and 25mV. Of that range, I am only interested in the 16mV to 22mV portion. The output should primarily be a DC signal, and the AC response, if any, ...
1
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1answer
302 views

ECG Circuit Simulation problems

I'm working on a TINA-TI circuit. I'm no expert in the electronics field or the medical engineering so I am having a hard time figuring out how to construct my ECG circuit. This signal will be ...
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2answers
113 views

Highly linear amplifier for tiny voltages

I have a tiny voltage which ranges between 0V to 0.05V (bandwidth of this signal is <100kHz) that I need to amplify to 0V to 3.3V. If I would like my final voltage to be distorted only upto 0.5%, ...
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1answer
64 views

AD623 ANZ vs. BNZ?

I have simulated my first circuit ever and now I wanted to order an Analog AD623 to actually build it. I gathered that I need the 8-DIP package to stick the IC on the breadboard, but there are ...
1
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3answers
140 views

Connecting strain gauge output terminals to an instrumentaiton amplifier

Before posing the question the figures are about as follows: In Figure 1 a strain gauge's outputs v1 and v2 is connected to an instrumentation amplifier’s inputs. For simplicity buffering part is ...
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1answer
82 views

Is an instrumentation amplifier design same with a standard op amp?

Is instrumentation amplifier nothing but a standard op-amp with a different configuration? I wonder if the inner complicated circuit of an instrumentation amplifier same with standard op-amp's. At one ...
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3answers
297 views

Mysterious Op Amp noise

I have a very good op amp (AD8551) that I use to dynamically amplify a very small signal (2x, 10x, 100x, 1000x gain). The problem is that there is a noticeable noise level at 100x and 1000x gain, and ...
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1answer
265 views

Noise reduction in physiological measurements (EEG/ECG) [duplicate]

I am building a hobby EEG and I am interested in quantifying how effective are the various noise reduction techniques. The basic circuit would be two electrodes going to an instrumentation amplifier. ...
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920 views

What does common mode voltage stand for in an instrumentation amplifier?

I was reading a text about instrumentation amplifiers. I couldn't find any easy explanation what really common mode voltage means and its importance.
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4answers
150 views

Three opamp instrumentation amplifier vs single opamp implementation

I read in a book three opamp instrumentation amplifiers are better and they are more common, but why is it better than the single opamp instrumentation amplifier? It must be more expensive as they ...
2
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1answer
87 views

Will an electrolytic capacitor work reliably with 0 VDC and 100 mVAC?

I ran across an instrumentation amplifier datasheet from "THAT Corporation", and noticed the polarized capacitor in series with the gain resistor: It is a typical 3 op-amp in-amp, so the ...
2
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3answers
221 views

The output of the amplifier changes depending on my distance

I made this circuit to amplify the output of a load cell. simulate this circuit – Schematic created using CircuitLab The instrumental amplifier has a Gain = 750. I use a dedicated ...
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0answers
198 views

Unexpected saturation with the rail to rail instrumental amplifier AD623

I'm trying to use the rail-to-rail instrumental amplifier AD623. Here the datasheet. simulate this circuit – Schematic created using CircuitLab First experiment: AD623 set as a voltage ...
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2answers
166 views

Which is the correct voltage reference for a single supply instrumentation amplifier?

I'm working on using the TI INA333 in a single 3v supply configuration. I need to create a "mid supply" (half V+) for the REF pin. I have thought of 3 ways to do this: Voltage divider with ...
2
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1answer
711 views

Multiple ADC readings in Arduino Uno with INA125 problems

First my system used four cheap resistive load cells (maks 5 kg, input 5 VDC) to measure COG of a quadrotor. The measurement pan dimensions are 60 cm x 60 cm and made from glass ...
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1answer
193 views

Is this circuit an instrumentational amplifier? Is there an error in the circuit?

I have found this OP AMPs (ADS1240 from TI) configuration in a datasheet (pg. 21) as an ADC input driver: simulate this circuit – Schematic created using CircuitLab Is is supposed to ...
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1answer
174 views

Is my Instrumentation Amplifier's Voltage Offset causing problems?

I am using a MCP6N11-100 to amplify the signal out of a 2mV/V Load Cell with a Excitation voltage of 10 V so the max. output (differential) would be 20 mV. The load cell is rated for 4000 KG. I am ...
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1answer
1k views

AD620 In-Amp, single 5v supply, reference pin affecting gain

Given the datasheet here, I can't explain my observations with my AD620AN test circuit. The circuit: Supply: +5v / 0v (Well regulated) 1k potentiometer across the supply, with the wiper going to ...
2
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1answer
400 views

Thermocouple signal conditioning - how to deal with low output swing margin of amplifier?

I have this thermocouple conditioning circuit. Let's say my gain is 100. Minimum low level for AD8237 is 20mV. As K type thermocouple outputs 40uV per 1C, I will have 4mV per 1 degree C. This ...
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2answers
333 views

subtract two AC voltages with instrumentation amps

I'm implementing the so-called "3 omega technique", where a thin metal line is excited with a sine current. The metal has a high TCR which causes a 3rd harmonic oscillation, and I need to measure the ...
3
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1answer
262 views

Understanding common mode vs output voltage graph for instrumentation amps

What are limitations on the design imposed by this graph? Say, if I want my output to span 0V - 3.3V, does this mean that I should position my input signal at 2.5V? edit: InAmp in question is ...
2
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3answers
1k views

Economical thermocouple amplifier circuit

I'm looking for the most economical circuit that reasonably accurate circuit for amplifying the voltage produced by a thermocouple (so it can be read by an ADC). For the sake of argument, component ...
2
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2answers
2k views

Load Cell Amplifier AD620

I know AD620 is an old part but it is available at my place. I intend to develop a Load Cell amplifier. Load cell is 2mV/V. I am planing to use AD620 for it. Following are my calculations: ...
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1answer
168 views

Read-out circuitry for resistive biosensor

I have a biosensor. It's resistivity changes while sensing the analyte I want. Resistivity of biosensor is around 10 Ohms. I normally use Keithley 2400 sourcemeter for experiments. I apply a constant ...
3
votes
1answer
325 views

MCP6N11 reference voltage problem

I am using the MCP6N11-010 in a current sensing circuit (Battery charger). i would like the output of the INA to show the difference in inputs starting from 0v going up to VDD but cant seem to get the ...
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1answer
129 views

Instrumentation Amp Voltage issue

Thanks for your help on the previous question. I set up my wheatstone bridge to pins 2 and 3 of the amp. When I use a voltmeter, I see differences over the bridge as a function of resistor change. ...
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1answer
624 views

What is the reference pin on an instrumentation amplifier used for?

Happy new year all! I'm wondering how to correctly use the reference pin on an INA128 Instrumentation Amplifier. Is there a way to use this pin to eliminate negative voltages (i.e. do a voltage ...
3
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2answers
2k views

How to Read Wheatstone Bridge negative voltage with Arduino?

I have a half bridge setup with strain gages and a INA126 to amplify the voltage. I can read the voltage fine when the lever is bent one way, but when beding the lever in the opposite direction I ...
9
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1answer
987 views

Why is my instrumentation amplifier's gain non-linear?

I am using an AD8226 instrumentation amplifier as the pre-amp in a circuit which uses a micro fuel cell oxygen sensor to measure oxygen content in a gas stream. The pre-amp is configured in single ...
3
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2answers
487 views

Charge Model vs Voltage Model for Piezo Electric Sensor

The following document describes signal conditioning circuits for Piezeoelectric sensors. I was interested in knowing which model should I use when designing signal conditioning circuit for ...
3
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1answer
1k views

Amplification of load cell signal with AD623 IC

I am trying to amplify the signal from a load cell using an AD623 instrumentation amplifier. Please refer to http://www.instructables.com/answers/Amplifying-load-cell-signal-with-AD623-problem/ for ...
2
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2answers
243 views

Instrumentation amplifier

I am using an instrumentation amp (http://www.linear.com/product/LT1168), and I am a bit confused why it is giving me a output voltage that I am not expecting. I am pretty sure, I am doing something ...
2
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4answers
1k views

Simple op-amp differential amplifier

EDIT: Thanks everyone, I got it to work: Now if only I could accept multiple answers... . . . Is the output of this op-amp circuit linear in input voltage? The last equation \$A = ...