NOTE: This is NOT an original YHDC clamp. We have a batch of YHDQ clamps, which is basically a YHDC clone. We received them from our supplier when we ordered YHDC clamps. They are listed at below cost. They seem to work fine, but might be a bit less accurate then the original. They look nearly identical, but are 10g lighter and the cable is a bit thinner. Also the coil resistance is about 175 Ohm, compared to 100 Ohm for the original YHDC. BE AWARE that most online sellers selling this item now ship YHDC clones! Exactly like this one. Most list it as YHDC, but they will send you a YHDQ(this item) or similar clone. We also have the original YHDC listed. We contacted many supplier in Asia who all have it listed as YHDC, and nearly all of them send photos of a YHDQ or other clone, even though their listing says YHDC. This is a Non-Invasive AC Current Sensor Clamp, also know as a CT Clamp. The SCT-013 is available in a couple of different versions. This version(SCT-013-000) is the most common one used, and will output 0 to 50mA when the measured wire is conducting 0 to 100A. It does NOT have an internal resistor. Normally it will be connected to a resistor on the target board that will convert the current (0-50mA) to a voltage. Current transformers (CTs) are sensors that are used for measuring alternating current. They are particularly useful for measuring whole building electricity consumption (or generation for that matter). The split core is particularly suitable for DIY use it can be clipped straight on to either the live or neutral wire coming into the building without having to do any high voltage electrical work. Common applications include current measurement, monitoring and protection of AC motor, lighting equipment, air compressor, etc.  Features Model: SCT-013-000 Brand: YHDQ - NOT YHDC Frequency Range: 50HZ-1KHZ Rated input Current: 100A Maximum input Current: 120A Core material: ferrite Coil Resistance: 175 Ohms Opening size: 13mm * 13mm Lead length: 1.5 meters Connector: Standard Φ3.5 three pin plug output ,current, voltage, two kinds of output forms (voltage output, built-in sampling resistor) Weight: 40g [mx_insert-post-ebay slug="ebay-t-default" no-class="mxPakInc, mxEbayTmpl"] Package Includes 20 x SCT-013-000 Clamp [mx_insert-post-ebay slug="ebay-t-default"] SKU: 20*SEN0-009 Category: Current & Power Sensors