Search results
Results from the WOW.Com Content Network
Loop-powered "I to P" (current to pressure) converters can convert the 4–20 mA signal to a 3–15 psi pneumatic output for control valves, allowing easy integration of 4–20 mA signals into existing pneumatic plant. Field instrumentation measurements include pressure, temperature, level, flow, pH or other process variables.
The second type of positioner is an analog I/P positioner. Most modern processing units use a 4 to 20 mA DC signal to modulate the control valves. This introduces electronics into the positioner design and requires that the positioner convert the electronic current signal into a pneumatic pressure signal (current-to-pneumatic or I/P).
A digital current loop uses the absence of current for high (space or break), and the presence of current in the loop for low (mark). [1] This is done to ensure that on normal conditions there is always current flowing and in the event of a line being cut the flow stops indefinitely, immediately raising the alarm of the event usually as the heavy noise of the teleprinter not being synchronized ...
Other signals are sent digitally on top of the 4–20 mA signal. For example, pressure can be sent as 4–20 mA, representing a range of pressures, and temperature can be sent digitally over the same wires. In point-to-point mode, the digital part of the HART protocol can be seen as a kind of digital current loop interface.
Showing the evolution of analog control loop signaling from the pneumatic to the electronic eras Current loops used for sensing and control signals. A modern electronic "smart" valve positioner is shown, which will incorporate its own PID controller.
In process automation traditionally most of the field transmitters are connected over a current loop with 4-20 mA to the controlling device. This allows not only to transmit the measured value with the level of the current, but also provide the required electrical power to the field device with just one two-wire cable of a length of more than a ...
They'll love this play kit that comes with a stethoscope, thermometer, syringe, blood pressure cuff, and so much more. KiwiCo is a company that encourages kids to explore STEM-related subjects, so ...
The processors receive information from input modules, process the information and decide control actions to be signalled by the output modules. The field inputs and outputs can be analog signals e.g. 4–20 mA DC current loop or two-state signals that switch either "on" or "off", such as relay contacts or a semiconductor switch.