hi everyone! i'm working on a project that would measure the total current up to 250 Amperes maximum. I plan to use a current transformer and read the corresponding current measurement through the use of a ADC0832 Analog to digital converter. Then i'll use an Atmel 89C51 to process the data an display the measurment in a LCD. Could anyone be willing to help me find a more appropriate circuit that i use to measure the readings from the current transformer to my analog to digital converter circuit...
Thanks in advance!!!
I suppose you have considered the alternative method: 250A shunt and ordinary digital mV meter? A lot cheaper than a current transformer, A/D converter and whatnot but, perhaps, you have a good reason to go the current transformer way? Just curious.
this project will be used to measure the total load current that lsupplied by a generator. So a current transformer is much more suitable for rugged environment and for this kind of applications.
This made me ponder... if you use a current transformer, and connect a shunt of fairly low, known resistance, across the CT terminals, then you could use a digital mV meter across the shunt. Hey presto, calibrate your shunt, such that 1 mV = 1A (primary), you got a 250A ammeter
Say you use a 800/5 CT (quite common):
At 250A primary, secondary current is 250/(800/5) = 1.5625A
If 1mV = 1A (primary), then shunt resistance = 0.250V/1.5625A = 0.16 ohm
Of course this is a theoretical value, might need to be adjusted in practice.
Well, I wanted to build a DC ammeter so I can use it in conjunction with my audio amp. See a MultiMeter doesn't give you something you can work with. If you wanted to integrate it into a system or something, you can't because you can't very well tell your STAMP or something to just read the multimeter. So is it possible to create using a transfomer and A/D and what way is going to make it the most accurate?
Agreed, but in this case, you are just using the multimeter as an ADC. As suggested, you can use a 250A shunt and use your basic stamp to measure the voltage across the shunt. Most shunts are designed so that their full scale corresponds to 50mV.