Current Transformers

These types of current sensors produce small voltages when exposed to a magnetic field created by a wire conducting electricity. The voltages are directly related to the current flow one wishes to measure. Split type current transformers a very simple to install as you clip them onto the wire you wish to measure. They only measure the electrical current [amperage] and not the voltage. So, you either assume the voltage stays the same or you measure the voltage separately and figure it into the final calculation of your energy usage in watts. Unmeasured and therefore unaccounted voltage fluctuations can considerably impact the accuracy of current transformer measurements. They do not perform well at measuring very low loads. Generally, they are the go-to choice for most applications because of their ease of installation and the fact that they do not require the opening of the electrical wiring, which requires an electrician. Output is typically a voltage below 3 volts or serial communication.

These types of current sensors place a high impedance resistor parallel to the load to be measured. The voltage drops across the resistor are directly related to the current flow. This allows the measurement of high current values by placing a resistor of low, known resistance in parallel with a voltmeter. Shunts are rated by their maximum current and voltage drop and have thermal limitations that affect their operation. They are considered accurate and cost-effective compared to alternative devices like Hall effect sensors and current transformers. They will require a licensed installer as opening the wiring is required. Output is typically 2 voltages, one representing the current.

This sensor is made by CCS (Continental Control Systems) - https://ctlsys.com/product/wattnode-pulse/ - and is a UL listed device to measure power consumption of 3-phase power devices. It is either wired in or can be hooked up using 3 CT’s. Output is typically a pulse or serial communication.