Controls & Instrumentation Guides
Practical explanations of the concepts behind the calculations. Learn how the signals, instruments, electrical circuits, and control systems actually work—and how to troubleshoot them in the field.
A Practical Learning Path
If you're learning controls or instrumentation, work through these subjects in roughly this order.
Getting Started
Start here if you're new to controls and instrumentation.
Understanding 4–20 mA
Learn what a 4–20 mA signal represents, why current is used, how LRV and URV work, and how to interpret a transmitter signal in the field.
4-20mA Signal Troubleshooting
A practical field guide for finding problems in 4–20 mA loops, from the transmitter and loop wiring through the analog input, PLC scaling, and HMI.
4-20mA vs 0-10V
Understand the differences between the 2 common analog control signals.
Square-Root Extraction & DP Flow
Understand differential-pressure flow measurement, why flow is proportional to the square root of DP, and where square-root extraction belongs in a control system.
PLC Analog Scaling
Follow a real analog signal from the transmitter, through the PLC input, from raw counts to engineering units and finally to the HMI.
4–20 mA & Instrumentation
Understand the signal that connects many field instruments to control systems.
4–20 mA Explained
Understand the complete 4–20 mA signal, including current levels, transmitter ranges, loop power, voltage burden, and measurement.
Troubleshooting a 4–20 mA Loop
A practical approach to diagnosing abnormal current, wiring problems, loop resistance, power issues, and incorrect controller readings.
Electrical Fundamentals
The electrical concepts that show up repeatedly in controls and instrumentation work.
Ohm's Law
Understand the relationship between voltage, current, resistance, and power—and how those relationships apply to control circuits.
Voltage Dividers
Learn how resistor networks produce predictable voltages and where voltage dividers appear in control and instrumentation circuits.
Temperature & Sensors
Learn how RTDs and thermistors convert temperature into measurable electrical characteristics.
RTD & Temperature Sensors
Explore PT100, PT1000, Ni1000, and 10k Type II sensors, including resistance-temperature relationships and the differences between sensor technologies.
2-Wire, 3-Wire & 4-Wire RTDs
Understand why lead resistance matters and how different RTD wiring configurations affect measurement accuracy.
PLC & Controls
Connect field instrumentation to the control system and understand what happens to the signal along the way.
PLC Analog Scaling
Understand raw analog input counts, signal ranges, engineering-unit scaling, and the relationship between transmitter and PLC configuration.
Analog Signal Scaling
Apply linear scaling to 4–20 mA, 0–10 V, raw PLC counts, and other proportional signals.
Technician Toolkit
We're building a collection of downloadable field tools, reference sheets, PLC scaling worksheets, calibration forms, and other resources designed to be useful at the panel, in the field, or at the engineering desk.
Explore the calculators →