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4-20 mA Scaling Formula:
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The 4-20 mA scaling formula is used to convert a process measurement into a standard 4-20 mA current signal. This current loop signaling is widely used in industrial instrumentation and process control systems.
The calculator uses the 4-20 mA scaling formula:
Where:
Explanation: The formula linearly scales any measurement within a specified range to the standard 4-20 mA current signal, where 4 mA represents the minimum value and 20 mA represents the maximum value.
Details: The 4-20 mA current loop is the industry standard for process control because it's resistant to electrical noise, can transmit over long distances, and provides a "live zero" (4 mA) that distinguishes a valid zero reading from a broken wire (0 mA).
Tips: Enter the process measurement value, the minimum value of your measurement range, and the maximum value of your measurement range. All values must use consistent units.
Q1: Why is 4-20 mA used instead of 0-20 mA?
A: The 4 mA "live zero" allows distinguishing between a true zero reading and a broken wire or power failure (which would show 0 mA).
Q2: What happens if the measurement exceeds the range?
A: The output will be below 4 mA (if below minimum) or above 20 mA (if above maximum), which typically indicates an out-of-range condition.
Q3: Can this formula be used for reverse acting signals?
A: Yes, by swapping the Min and Max values, you can create a reverse acting signal where 4 mA corresponds to the maximum and 20 mA to the minimum.
Q4: What are common applications of 4-20 mA signals?
A: Temperature, pressure, flow, level, and analytical measurements in industrial process control systems.
Q5: How accurate is this conversion?
A: The formula provides a linear conversion. Actual accuracy depends on the precision of your measurement device and transmitter.