Hi Folks,
I am trying to interface a current sensor module with Arduino. The sensor module should sense current value less than 0.9mA from the external circuitry. Which is the best current sensor to buy of this purpose?
Thank you in advance!

 

Can you give us some insight on what "best" might look like. One man's trash is another man's treasure, and vice versa.

 

Measuring the current using shunt resistor isn’t acceptable? For such a low current it is prob. best option.

 

Since a Hall sensor measures the Hall Voltage of a magnetic field, are you of the opinion that you can infer the magnitude of the current that produces the magnetic field?

 

For that low current level, you will have to use a shunt resistor plus an opamp.
That is, if you expect any accuracy at reasonable prices.

 

For that low current level, you will have to use a shunt resistor plus an opamp.
That is, if you expect any accuracy at reasonable prices.

If I am using opamp and shunt resistor circuitry, how can i power up opamp from Arduino, opamp needs +vcc and - vcc ryt?

 

Can you give us some insight on what "best" might look like. One man's trash is another man's treasure, and vice versa.

I just need a current sensing circuitry, for measuring low value currents...

 

Can you give us some insight on what "best" might look like. One man's trash is another man's treasure, and vice versa.

Best i mean more accuracy

 

Best i mean more accuracy

How much accuracy do you need? Do you know how to specify what you need?

 

How much accuracy do you need? Do you know how to specify what you need?

0.5% accuracy

 

Maybe use an opto-coupler?

 

0.5% accuracy

So if you are measuring 900 μA and you want to be within ±0.5% that would correspond to ±4.5 μA. Now tell me how a reading from a hall Effect sensor will allow you to determine the current with that level of accuracy.

 

If I am using opamp and shunt resistor circuitry, how can i power up opamp from Arduino, opamp needs +vcc and - vcc ryt?

We don't have enough information to give you a good answer.
What is the circuit of which you are trying to measure its current?
What is the maximum value of series current measurement resistor it can tolerate?
What is the electrical relationship of the circuit power supply with respect to the Arduino supply?

 

If I am using opamp and shunt resistor circuitry, how can i power up opamp from Arduino, opamp needs +vcc and - vcc ryt?

Most modern opamps will work from a single supply. There are some minor modifications you need to make when going from a dual supply to a single supply configuration.

 

I asked the questions in message #13 because it may be possible to make the current measurement without using an op-amp.

 

what is the stigma with using opamps? and why not use one designed for current sensing?

something like INA139/169 or similar may be a good choice and it is a low cost, compact device.


i never understood types asking for advice but not stating the problem with enough of details or answering the questions.
is this 'up to 0.9mA' circuit isolated or not? what is it? what voltage drop is tolerable? what is the voltage at point where current measurement is to be taken? is the measurement supposed to support bidirectional current?

 

We don't have enough information to give you a good answer.
What is the circuit of which you are trying to measure its current?
What is the maximum value of series current measurement resistor it can tolerate?
What is the electrical relationship of the circuit power supply with respect to the Arduino supply?

We don't have enough information to give you a good answer.
What is the circuit of which you are trying to measure its current?
What is the maximum value of series current measurement resistor it can tolerate?
What is the electrical relationship of the circuit power supply with respect to the Arduino supply?

Currently, I am using a test set up like this for measuring current and voltage. For peak to peak voltage 3.7V, I am getting current less than 1.3mA. I want to replace these multimeters, and automate measurements using Arduino board. While searching online, I came across Hall effect sensors and current sensing circuits, that's why I posted my query here for advice.
View attachment 313326

 

Use a shunt resistor and take two voltage measurements.

 

First I suggest you give this a read. Application Brief Precision, low-side current measurement. The problem you face is with such a low level current measurement is noise. The link suggest several rail to rail suitable operational amplifiers which are single supply and designed to measure low level voltage from current shunts.

Ron

 

Currently, I am using a test set up like this for measuring current and voltage. For peak to peak voltage 3.7V, I am getting current less than 1.3mA. I want to replace these multimeters, and automate measurements using Arduino board. While searching online, I came across Hall effect sensors and current sensing circuits, that's why I posted my query here for advice.
View attachment 313326

You offered no evidence that a Hall Effect sensor would be able to do the job. They don't measure current they measure magnetic fields and the field around a wire carrying 1 mA is miniscule. I estimate that 1 mA at 0.125 inches from a wire produces a magnetic field of 62.99 nanoTesla. I'm not sure there is a Hall Effect sensor that can measure that small field. 2mT seems to be about as small as they go. That is between 4 and 5 orders of magnitude smaller than a 2mT sensor can measure.