Precise current measurement upto .05uA

I am working on a circuit where i have to measure currents from -500uA to 5mA. For this i am using 100ohm resistor for converting current to voltage and then this voltage is sent to OP07 and output of this is given to HP7840 isollator whose gain is 8. circuit is working correctly for higher currents but i want to measure .05uA. But since output of this circuit is fluctuating when i am taking readings in 5 decimal points, due to this my readings are not coming accurate. I have no idea why their is fluctuations upto 0-100uV which is not desired. OP07 thermal noise is 0.2uV/`C and HP-7840 have only 0.1% nonlinearity.

Replay

The input noise of a OP7 is about 11nV/√Hz. The bandwidth (unless your circuit reduces it) is about 1MHz, so the expected input noise is about 10uV. With a gain of 8 the output noise is about 80-90uV.

You need to reduce the bandwidth. Work out how often you actually need a measurement, and add low-pass filtering with a roll-off at about double the measurement rate.

Depending on your exact requirements, you might find a transimpedance amplifier a better fit than a series resistor & voltage amplifier.

Category: op amp Time: 2016-07-28 Views: 0
Tags: op amp

Related post

  • A question on precise resistor measurement for current loops 2015-07-13

    For a current outputting device I'm using a data acquisition board which can only measure voltages. To translate the currents to voltages I use similar to the following shunt resistor: http://docs-europe.electrocomponents.com/webdocs/13ec/0900766b813

  • Current multiplier/divider for current measurement? 2012-05-10

    You can change a current mirror into a multiplier/divider by adding transistors on either side. Then the number of transistors defines the current ratio. The transistors have to be integrated on the same chip to have a good precision (good matching),

  • Inexpensive multimeter for integrated current measurement 2013-03-05

    I'm building a simple circuit with an Arduino Nano board, which will read signals from a Hall sensor and periodically send pulses to a small 5V solenoid. I'll drive it from 6xAA batteries in series, producing 7.2V. The on-time of the solenoid will be

  • Voltage and current measurement of battery Single ended or differential? 2015-06-30

    I am trying to measure battery's current and voltage for a battery charging/monitoring project. I have read all about current sensing (including high side & low side sensing). And i have decided to use Shunt resistors for current measurement as they

  • Shunt resistance VS Rogowski Coil in current measurement , which one is better? 2011-10-31

    Shunt resistance VS Rogowski Coil in current measurement , which one is better ? Just for reference I want to create small circuit that measure the power , so which one I go for ? UPDATE 1 : I'm measuring AC current Isolation is required Scale of cur

  • Current measurement with a multimeter: how am I doing it wrong? 2012-07-24

    I want to measure the current draw of a strip of LEDs. This depends on the intensity of the pattern the strips are running so I need to do it in "real time" to get an accurate idea, rather than just do maths from the spec sheet. I made this cabl

  • Current measurement in component level of an embedded system 2012-10-19

    I have an embedded system with a MCU, GPS module, GSM module and TI module. The project is largely depend on the total battery consumption. In order to characterize battery consumption, I have to measure current with respect to each module from the e

  • Current measuring with PIC 2013-01-18

    I know it is possible to measure analog voltages with the ADC peripheral of advanced PIC microcontrollers. There is no peripheral to measure current though. Is it possible to convert a current to a voltage so that I can measure that voltage with the

  • Low TC resistors for current measurement 2013-07-12

    I have a back-burner project to take an old bench power supply and retro-fit it with two 4 digit LED displays for current and voltage. The power supply is 3A/30V, so four digits means 3000 count and 12-bit conversions (4096 = 2^12). I've been trying

  • Correct negative current measurement but incorrect positive measurement 2013-07-21

    I'm trying to replicate a simple circuit that I designed in SpiceIV. Here's what it looks like I should be getting ~23 mA of current flowing through this circuit by ohm's law. However, when I measure it using my multimeter if I connect the COM lead t

  • Current measurement maximum time 2013-12-02

    On my multimeter I have two current measurement connection. One for the mA and one for the A. On the ampere one there's a time limitation but not on the mA one. Also they mention in the manual a kind of "cooldown time" after the measurement for

  • Simple PWM regulator, current measurement without high-side current sensing 2014-06-13

    I have a very simple Lead-Acid battery charger with slow (1kHz) PWM regulator. I would like to add current and voltage measurement (with PIC18F ADC - 200kSPS). I have no problem with voltage measurement, but I'm not sure about my shunt and current me

  • Help: need a compact shunt resistor for current measurement 2015-05-31

    I'm very new to electronics and learning as I am working on a project. I am trying to find a small compact replacement for the very large shunt that comes with a Current Meter I bought on ebay. Can anyone advise me on how to calculate an appropriate

  • Could you explain how this current measurement circuit works? 2015-06-15

    I have a schematic for current measurement, but I don't really know how can I calculate the output of it. The op-amps are on +-12V. The output of the circuit is 0.2*I(Rs) [V] (--> this is what I don't know how to calculate), thus in the range of 5V,

  • Using multiple current sense resistors in parallel to handle a high current measurement with cheaper resistors 2015-06-21

    I am measuring the current going to a motor using current sense resistors; however, in order to get a resistor that can handle the proper power, the price goes up way too much. My question is, can I use multiple lower power rated resistors in paralle

  • shunt current measurement with less voltage 2015-08-06

    Are there shunts available in market which can measure current of more than 200A but with voltage less than 50mV? --------------Solutions------------- Yes there are ! 200A at 50mV (max) means a 0.25mOhm(max) shunt. A quick google for "0.1mOhm shunt&q

  • Multichannel voltage/current measurement device 2015-08-08

    I'm building a 4 channel voltage and current measurement device. 2 channels for voltage (ac 0-300V rms and dc 0-300V) 2 channels for current (ac 0-5A rms and dc 0-5A) There is a central microcontroller (ATMEGA48) which selects which of the 2 channels

  • Simple current measurement solution and testing its validity 2015-09-19

    I have tried to measure current using SparkFun Hall-Effect Current Sensor Breakout - ACS712 and also tried using shunt resistor. It seems that each measured value is different from what I measured by multimeter. And I don't know which one is showing

  • Can 3-phase FOC control be done without current measurement? 2016-01-13

    Can a FOC control scheme be done using a rotary encoder to measure the position, speed and acceleration directly, or is measuring current necessary? FOC is a motor control scheme as described in links below: http://www.atmel.com/Images/doc32126.pdf h

iOS development

Android development

Python development

JAVA development

Development language

PHP development

Ruby development

search

Front-end development

Database

development tools

Open Platform

Javascript development

.NET development

cloud computing

server

Copyright (C) avrocks.com, All Rights Reserved.

processed in 0.486 (s). 13 q(s)