Week 7 Update - Current Transformers

Hello

Remember last week, how I used a current transformer in order to measure the voltage coming from the Light Bulb. Turns out it was actually a Current Transducer and I did not need the Resistor. With the resistor I get 52 millivolts and without it I get around 170 millivolts. Anyway, I calculated the Amperage using Ohm's Law which was 50 Watts (Wattage Rating for the Bulb)/120 Volts = 0.416 Amps. 

Remember how this current transducer is 5 Volts to 10 Amps. This means that 5 Volts gives me 10 Amp, 2.5 Volts gives me 5 Amps, 1 Volts gives me 2 Amps, etc. There's a pattern here. Volts multiplied by 2 gives me the Amps. So, I multiplied 170 millivolts by 0.001 to get 0.17 Volts which I then multiplied by 2 to get 0.34 Amps. My professor then removed the current transducer and used a Clamp-On Ammeter and got 0.34 Amps.

Now, I understand that a Current Transformer works like a Step-Down Transformer in that the current on the primary and secondary are proportional to one another. The primary has a larger current and the secondary has a smaller current. I plan to re do what I did last week with the Light Blub and integrate this with my BASpi. 

Anyway, I got an ELKOR SCT2-101 Current Transformer, which I included a picture of above. I replaced the current transducer from last week with this and set to work and put a 1K Ohm Resistor between the Hot and Neutral (Black and White) wires because without it the Circuit would gain extremely high voltages and kill me. This CT has a ratio of 100:5 which means that 100 Amps gives my 5 Amps, 50 Amps gives me 2.5, and 10 gives me 0.5. I calculated the amperage by dividing 60 Watts/120 Volts and got 0.5 Amps.

To get the expected voltage from my Multi-Meter,I divided 0.5/20  which is 0.1/4 which equals 0.025 millivolts. 0.025 multiplied by 1000 gives me 25 Volts. But, I ran into a roadblock, I didn't see 25 Volts displayed on my Multi-Meter so I changed the orientation of the CT a handful of times, as well as, replacing the 1K Resistor with 100 and 10K Resistors. Nothing. I got a Clamp on Meter which I included a picture of and measured the Voltage between the CT wires and got 0.2 Volts. Weird. But, this CT wasn't really useful in what I needed.

I then replaced that CT with a Micro Switch CSALA1CD Linear Current Sensor which you can see below:

This one had 3 pins and needed 8-16 Volts DC to operate, so I hooked up 2 of the pins to DC Variable Power Supply and the last pin to my Multi-Meter and ground.Turns out the Voltage reading is half of what you see on the power supply so 8 Volts = 4 Volts, 10 Volts = 5 Volts, etc.But, the data sheet says the Sensed Current is 57,but gave no unit. My professor came in to help me and he was also confused, more on which pins are what because the data sheet gives a side view and doesn't indicate which side. So was prong 1 Vcc or Ground? We didn't know. After some trouble-shooting we found that there was no current reading on my Multi-Meter, so we connected a Variac to control the brightness of the light, but the voltage reading stayed the same. Strange. 

Here are the datasheets for both CTs along with pictures of my setup:
http://www.elkor.net/pdfs/SCT2.pdf 
https://sensing.honeywell.com/honeywell-sensing-current-csla-series-catalog-pages.pdf

- Valentin