4-20 mA Current Loops Overview The 4-20 mA current loop is the prevailing process control signal in many industries. It is an ideal method of transferring process information because current does not change as it travels from transmitter to receiver. It is also much simpler and cost effective.
What voltages are used with a 4-20 mA current loop?
There are many common voltages that are used with 4-20 mA current loops (9, 12, 24, etc.) depending on the particular setup.
How do I display the output of a 4-20 mA transmitter?
Go with the Helios PD2-6000 when you need a large display meter to display the 4-20 ma output from any transmitter you might have. The PD2-6000 can display that output in six full digits and will also provide the 24 VDC to power the transmitter.
What is the low end of an analog loop called?
An analog signal range that has a non-zero low-end, such as 3 to 15 PSIG or 4 to 20 mA, is known as a “live-zero”range because the low end is not dead, but has some pressure, voltage, or current present at all times. Before the 1970s, most analog loops were 3 to 15 PSIG pneumatic loops.
What is a 2-wire 4-20mA control loop?
In two-wire 4-20mA control loops, we use 2-wire transmitters to convert various process signals representing flow, speed, position, level, temperature, pressure, strain, pH, etc., to 4-20mA DC for the purpose of transmitting the signal over some distance with little or no loss of signal.
What is a 4-20mA transmitter?
This is the most common configuration of modern 4-20mA transmitters. The transmitter and control panel can use the same 24V and 0V dc supply lines. The 4-20mA signal flows through the 24V dc line and the signal line to the controller. Only three cable cores are required to the transmitter.
Where does the power to drive the 4-20mA loop come from?
It is assumed that the power to drive the 4-20mA loop is derived from the control panel. Electrical interference on the voltage supply lines will not be transferred to the 4-20mA signal line, reducing the risk of spurious signals being received at the controller.
