# Connecting an ADC to USB port

#### dukakisomondi

Joined Jan 5, 2023
1
I have a current transformer(Rogosci coil) that has a range of 0-5V DC. My PC has a USB 3.0 port.
The coil will need to be connected to an ADC, which has a parallel output, which needs to be connected to the USB port.
I will write the software to process the data.
Any idea on how to proceed?

#### DickCappels

Joined Aug 21, 2008
9,632
How are you with microcontrollers?

#### crutschow

Joined Mar 14, 2008
31,580
Likely the easiest would be to buy an A/D to USB board, perhaps one like this.
Its max input conversion voltage is 3.3Vdc, but you could use a resistive divider to reduce the 5V from the coil to 3.3V.

Last edited:

Joined Jan 15, 2015
7,149
I have a current transformer(Rogosci coil) that has a range of 0-5V DC. My PC has a USB 3.0 port.
A CT (Current Transformer) is an AC device. This would go much better if you can provide a link to exactly what you have. There are CTs which will output a DC voltage proportional to the AC current measured. These are more than just a CT. The latter are often called a Current Transducer and they look like this. How to interface exactly what you have to what you want to do starts with exactly what you have? Next your choice of ADC will determine both the accuracy and resolution of your measurements. Finally with AC current transducers there are Average RMS Current Transducers and Transmitters as well as True RMS Current Transducers depending on the AC current you want to measure.

Just for example if I have a 10 bit ADC with a 0 to 5 volt input the best resolution will be 5 / 1024 = 0.00488 volt or about 4.88 mV. Using a 0 to 50 Amp AC current transducer becomes 0 to 50 AAC = 0 to 5.0 VDC or 5.0 / 50.0 = 0.1 volt per amp. You write your code accordingly. Today 12 bit ADCs are low cost and abundant.

Anyway you choose an ADC based on what you want. Since you have a 0 to 5 VDC signal you may want to consider an ADC with a 0 to 5 VDC input range. That or if you get a 3.3 volt input range dividing your AC transducer out down and scaling in your code.

Ron

#### DickCappels

Joined Aug 21, 2008
9,632
Rogowski pickup coils usually need frequency compensation, so it is reasonable that this is a bit more than coil.

Joined Jan 15, 2015
7,149
Rogowski pickup coils usually need frequency compensation, so it is reasonable that this is a bit more than coil.
That would be my thinking.

Ron

#### kaindub

Joined Oct 28, 2019
114
A Rogowski coil is a current transformer. A Rogowski coil outputs a voltage proportional to the current, whereas a traditional current transformer outputs a current proportional to the input current
Rogowski coils are very accurate and have a very large frequency response, which is why they are used mostly in measuring circuits. (not power circuits)
As with all current transformers used for AC, the Rogowski coil output needs to be rectified and then measured (usually by an RMS calculation). You cant just use diode rectification as you lose the diode threshold voltage, so an op amp based rectifier before your ADC is required.

#### nsaspook

Joined Aug 27, 2009
10,929
Another possibility if you're writing custom software and building hardware for USB interfacing.