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 ...

learn more… | top users | synonyms

3
votes
1answer
222 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 ...
0
votes
0answers
19 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 ...
0
votes
2answers
46 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
votes
3answers
97 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
votes
1answer
80 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 ...
1
vote
1answer
46 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 ...
1
vote
1answer
80 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
votes
2answers
79 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
votes
1answer
69 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 ...
0
votes
1answer
126 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
163 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 ...
0
votes
1answer
82 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.
0
votes
2answers
77 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 ...
-3
votes
2answers
145 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.
4
votes
3answers
242 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 ...
0
votes
0answers
59 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
votes
2answers
68 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" ...
1
vote
1answer
218 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 ...
1
vote
2answers
735 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 ...
0
votes
1answer
125 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 ...
1
vote
1answer
1k 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. ...
1
vote
2answers
404 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 ...
1
vote
1answer
1k 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, ...
1
vote
2answers
139 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
votes
1answer
262 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
votes
1answer
119 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
vote
1answer
379 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 ...
1
vote
2answers
128 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%, ...
0
votes
1answer
73 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
vote
3answers
164 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 ...
4
votes
1answer
90 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 ...
7
votes
3answers
323 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 ...
1
vote
1answer
369 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. ...
0
votes
2answers
2k 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.
1
vote
4answers
162 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
votes
1answer
94 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
votes
3answers
248 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 ...
1
vote
0answers
233 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 ...
2
votes
2answers
195 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
votes
1answer
782 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 ...
5
votes
1answer
200 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 ...
1
vote
1answer
198 views

Is my instrumentation amplifier's voltage offset causing problems?

I am using an MCP6N11-100 to amplify the signal out of a 2 mV/V load cell with a excitation voltage of 10 V, so the maximum output (differential) would be 20 mV. The load cell is rated ...
0
votes
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
votes
1answer
465 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 ...
4
votes
2answers
362 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
votes
1answer
300 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
votes
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
votes
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: ...
1
vote
1answer
175 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
336 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 ...