I want to order a non-invasive current sensor for my little project and need to understand what CT do I need. I have many questions but they all interrelated to each-other. I try to explain what I mean.
I will use a current transformer with 5V Arduino to monitor energy consumption. Speaking of 5V and the alternating current I want to mention that ADC will use only the 2.5V range of analog pins, as measured voltage is an AC. Maximum expected current value is 30A. I came across with a quite affordable SCT-013 series transformers from manufacturer YHDC on Ebay. Interestingly they have different amperages from 5A to 100A. All transformers has a Burden resistor exept first 100A that only have a Zener diode to limit the output voltage. I don't know whether I have to buy 100A CT without a resistor and customise it or just buy a 30A one...
You can just explain those two questions:
Why do those current transformers does have a amerage value? Of course many things evolwed here. But most importantly, they just have different number of turns and different Burden resistors. Build construction could be the same and seems to me the same. Can I not use 100A CT that has no in build resistor and calculate my own resistor value to make it eg. 10A for 5V ADC? What is the reason putting a resistor in instead of letting the people choose their best?
If I calculate the value of Burder resistor for SCT-013-030 that has 30A input current in respect to 5V Arduino, it makes 106 Ohms.
I(peak primary) = 1.414 * 30 A = 42.42 A
I(peak secondary) = 42.42 A / 1800 turns = 0.02356666666 A
R(Burden) = 2.5 V / 0.02356666666 A = 106.082037 Ohm
But why it has a 62 Ohm Burden resistor? Why it has to have a 0-1V output?