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Selecting Current Operated Switches and Relays for Your Application
NK Technologies offers a wide range of current operated switches and relays. Selecting which model will work best requires some knowledge of the specific application.
The first thing to consider is the output action. As a practice, NK Technologies defines the output contact in the “out-of-the-box” or shelf state (without current passing through the sensing window).Does the application require a closed output when the sensed current exceeds the setpoint? That would mean a normally open output is needed. Normally open (NO) outputs will close when the current exceeds setpoint, and normally closed (NC) outputs will open when current exceeds setpoint.
Next, what will the output contact do for you? If it will be used as an input to a programmable logic controller (PLC), the “universal” output (NOU or NCU) would be the best choice. They can control AC or DC powered logic, with a wide range of maximum voltages. If the output will be used to control the coil of a relay or contactor, the control logic will likely be AC, under 240 volts. We recommend using a sensor with higher capacity than the “universal” type, so select a model with NOAC or NCAC. As long as the controlled load operates at less than one amp continuously, this output can handle the load.
Does the application require a delay before the output changes state with current increasing? The ASX and ASXP series have a delay of up to 15 seconds built into the sensor.
Can the monitored circuit conductor be threaded through the sensor opening? Select the solid-core models. If the monitored circuit must remain connected, select the split core models. Also check the outside dimension of the conductor before placing any orders, to be sure that the conductor will fit through the sensing window. |
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AS1 Series: Provides the low capacity universal output type, with a wider hysteresis at the low end of the single range, narrowing as the set point is adjusted to the high end of the range.
ASX Series: Has an adjustable start-up/delay timer which allows a 0–15 second delay to eliminate nuisance trips from high inrush or short overload conditions, and a very constant hysteresis. The sensor can be ordered with either the universal contact or with the one amp AC output.
ASXP Series: Deviates from the other current switch models in several ways. Models can be selected which are powered from 24 volts (AC or DC) or from 120 volts (AC or DC). This series has very constant hysteresis, the set point adjustment uses a single turn potentiometer with the trip point indicated on the label, time delay on current rise and the electromechanical relay output can switch up to 5 amps AC or DC.
AS0 Series: Requires an external power supply, but the trip point can be adjusted to change state (solid state contact) with current as low as 3 mA.
APMR Series: A unique product. By using external current transformers and comparing the current being used with the system voltage, it provides two independent relays which can be adjusted to change state at an increasing or decreasing wattage magnitude. This product also produces a 4–20 mA signal directly proportional to the watts being consumed. This device is ideal when the monitored load is critical, or in applications where poor power factor reduces the linearity of the current rise.
In addition to these models, NK Technologies has a number of specialized current switches and relays with extra features which may make them perfectly suited for your application. Please visit our products page for more product information. Please contact the factory if you need help selecting a sensor. Our support and engineering team willl help select a sensor that will work best for you.
Get PDF Version Here
AS1 Series Data Sheet
ASX Series Data Sheet
ASXP Series Data Sheet
AS0 Series Data Sheet
APMR Series Data Sheet |
