Top 100+ Instruments Interview Questions and Answers for Engineers
Published on July 3, 2025 | Category: answer
Instrumentation engineering plays a crucial role in industries like oil & gas, pharmaceuticals, power plants, manufacturing, and automation. Whether you’re a fresher preparing for your first job or an experienced professional aiming for a better opportunity, having a solid grasp of instrumentation basics and practical knowledge is essential.
This comprehensive guide provides a curated list of 100+ top instruments interview questions and detailed answers covering the most important topics in instrumentation. It includes questions on sensors, transmitters, controllers, process variables, PLC, SCADA, HART protocol, calibration techniques, pressure switches, thermocouples, RTDs and more.
All questions are structured to help you understand both the theoretical concepts and real-world industrial applications of instrumentation. This list is designed to help you succeed in technical interviews for roles such as:
- Instrumentation Engineer
- Instrumentation Technician
- Control System Engineer
- Maintenance and Field Engineer
- Automation Engineer
Use this page as your go-to preparation resource for interviews in leading companies and government sectors.
Topics Covered in this Interview Guide:
- Process Measurement and Control
- Field Instruments: Transmitters, Sensors, Switches
- PLC and SCADA Basics
- Calibration and Standards
- Loop Checking and Troubleshooting
- Control Valves and Pneumatic Instruments
- Industrial Communication Protocols (HART, Modbus, Profibus)
Let’s dive into the most important and frequently asked instrumentation interview questions and answers that will help you stand out in your next interview.
1. What is Instrumentation?
Instrumentation is the science of measuring and controlling physical quantities such as pressure, flow, temperature, level, and distance. It involves sensors, transmitters, and control systems used to automate industrial processes.
2. What is the Importance of Instruments?
Instruments are essential for:
- Maintaining product quality and consistency
- Ensuring process safety
- Achieving energy efficiency
- Automating manual operations
They are the backbone of modern industrial automation.
3. What is the Role of Instruments in Safety, Process Control, and Feedback?
Instruments provide real-time measurements to:
- Safety: Trigger alarms and shutdowns in abnormal conditions
- Process Control: Adjust valves, motors, etc., to maintain desired parameters
- Feedback: Send actual values to the controller for closed-loop control
4. Name Some Instruments You Work With
Commonly used instruments include:
- Pressure transmitters
- Temperature sensors (RTD, Thermocouple)
- Level transmitters
- Flow meters (Magnetic, Vortex)
- Control valves
- Proximity sensors
5. What is Temperature Measurement?
Temperature measurement refers to detecting the degree of heat in a process or object using sensors like thermocouples, RTDs, or infrared sensors.
6. What are the Types of Temperature Measuring Instruments?
- Thermocouple (TC)
- Resistance Temperature Detector (RTD)
- Thermistors
- Infrared temperature sensors (non-contact)
- Bimetallic temperature sensors
7. What is a Thermocouple?
A thermocouple is a temperature sensor formed by joining two dissimilar metals. When heated, it generates a small voltage proportional to temperature.
8. What are the Types of Thermocouples?
- Type J (Iron – Constantan)
- Type K (Chromel – Alumel)
- Type T (Copper – Constantan)
- Type E, N, R, S, B (for high temperature applications)
9. What is the Output of a Thermocouple?
The output of a thermocouple is in millivolts (mV), typically ranging from 0 to 50 mV depending on the type and temperature.
10. How Does a Thermocouple Connect to a PLC?
Thermocouples are connected to PLCs using:
- A thermocouple input module
- Cold junction compensation (CJC) terminals
- Shielded thermocouple extension wires
11. How Does a Thermocouple Work?
It works on the Seebeck effect, which states that a voltage is generated when two different metals are joined and their junctions are at different temperatures.
12. What is the Working Principle of Thermocouple (Seebeck Effect)?
When two dissimilar metals are joined at one end (hot junction) and the other ends (cold junction) are kept at a reference temperature, a voltage (Seebeck voltage) is generated based on the temperature difference. This voltage is proportional to the temperature.
13. What is the Hot and Cold Junction in Thermocouples?
- Hot Junction: The point where two dissimilar metals are welded – placed in the process to measure temperature.
- Cold Junction: The reference junction, usually connected to the PLC or transmitter, maintained at known temperature or compensated electronically.
14. What is the Temperature Range of Different Thermocouple Types?
- Type J: -40 to 750°C
- Type K: -200 to 1260°C
- Type T: -200 to 370°C
- Type R, S, B: Up to 1600°C
15. Which is Preferred for Temperature: RTD or Thermocouple?
Use RTD for high accuracy in lower temperature ranges (up to 600°C). Use Thermocouple for wider temperature range and high-temperature environments.
16. Can We Connect a Thermocouple Directly to PLC?
No, thermocouples need a dedicated thermocouple input module that provides cold junction compensation and signal amplification.
17. What Type of Module is Required for Thermocouple Connection to PLC?
A dedicated Thermocouple Input Module is required. It must match the thermocouple type (e.g., K-type, J-type) and provide CJC.
18. What Are the Various Temperature Ranges of Temperature Instruments?
- RTD: -200 to 600°C
- Thermocouple: -200 to 1600°C
- Thermistor: -50 to 150°C (more sensitive, narrow range)
- Infrared sensor: -50 to 3000°C (non-contact)
19. What is the Difference Between RTD and Thermocouple?
| Feature | RTD | Thermocouple |
|---|
| Output | Resistance (Ohms) | Voltage (mV) |
| Accuracy | High | Medium |
| Range | -200 to 600°C | -200 to 1600°C |
| Cost | More expensive | Cheaper |
20. What is RTD?
RTD stands for Resistance Temperature Detector. It measures temperature by correlating the resistance of the RTD element with temperature. The most common RTD is the Pt100.
21. Types of RTD
- Pt100 (Platinum, 100 ohms at 0°C)
- Pt1000 (Platinum, 1000 ohms at 0°C)
- Nickel and Copper-based RTDs
22. How Many Types of Wires Are in RTD?
- 2-Wire RTD – Simple, but less accurate (prone to lead resistance error)
- 3-Wire RTD – Most common, compensates for lead resistance
- 4-Wire RTD – Most accurate, used in laboratories and precision systems
23. Why is RTD Preferred Over Thermocouple?
RTDs provide better accuracy, stability, and repeatability, especially in the range of -50°C to 500°C. They are ideal for quality-sensitive applications.
24. RTD Basic Formula for Temperature Conversion
RTD resistance changes with temperature and follows this formula:
R(T) = R0 × (1 + α × ΔT)
Where:
R(T) = Resistance at temperature T
R0 = Resistance at 0°C (usually 100 ohms)
α = Temperature coefficient of resistance (~0.00385/°C)
25. For Pt100 RTD, What is the Normal Temperature Range?
The typical operating range of a Pt100 RTD is -200°C to +600°C.
26. Explain RTD Working Principle
RTD works on the principle that the electrical resistance of metals increases with temperature. As temperature rises, the resistance of the RTD element (like platinum) increases, which can be measured to determine temperature.
27. Which Wiring is Mostly Used in RTD Configuration?
The 3-wire RTD configuration is most commonly used in industry as it provides good accuracy while compensating for lead wire resistance.
28. How to Connect PLC to RTD?
To connect an RTD to a PLC:
- Use an RTD input module (3-wire or 4-wire compatible)
- Connect the RTD wires as per module terminals
- Scale the input in the PLC program to engineering units (°C)
29. Basic Principle of RTD
RTD operates on the principle that a metal's resistance increases with temperature. This linear resistance change helps accurately determine temperature.
30. How Does PLC Work with RTD?
The PLC reads resistance from the RTD via the analog RTD input module. It converts the resistance to temperature using internal scaling logic or formula.
31. What is the Output of RTD?
RTD does not generate voltage. Its output is resistance (in ohms) which changes with temperature.
32. Maintenance of RTD
- Ensure tight and clean connections
- Protect sensor from vibration and corrosion
- Verify calibration periodically
- Check cable insulation and shield grounding
33. What is the Maintenance of a Thermocouple?
To maintain a thermocouple:
- Check for corrosion or damage on the junction
- Ensure correct insulation and shielding of wires
- Verify cold junction compensation is functioning
- Calibrate periodically using a reference source
- Keep junction clean and free from oxidation
34. How to Install an RTD?
Steps to install an RTD:
- Insert RTD into a thermowell (if used)
- Ensure proper insertion length for accurate reading
- Connect 2, 3, or 4 wires based on the system
- Use proper gland and ensure grounding
35. How to Install a Thermocouple?
Installation steps:
- Mount thermocouple securely near the measurement point
- Use extension wires of the same type
- Ensure proper polarity (positive to positive, negative to negative)
- Use thermowell in high-pressure or corrosive environments
36. How to Check If RTD is Working or Not?
- Measure resistance with a multimeter (Pt100 should show ~100Ω at 0°C)
- Check for open or short circuit
- Verify reading using a reference thermometer
37. How to Check If Thermocouple is Working?
- Heat the tip and observe mV output
- Use a multimeter in mV range
- Compare with temperature-mV chart
- Check polarity and continuity
38. What is a Pyrometer?
A pyrometer is a non-contact temperature measuring instrument used to measure high temperatures from a distance using infrared radiation.
39. How Does a Pyrometer Work?
A pyrometer measures temperature by detecting the infrared energy emitted by a hot object and converting it into a readable temperature value.
40. Basic Principle of Pyrometer
It works on the principle of blackbody radiation. All objects emit infrared radiation based on their temperature. The pyrometer detects this radiation and calculates temperature.
41. What is the Output of a Pyrometer?
Pyrometers typically provide:
- Analog output (4–20 mA or 0–10 V)
- Digital output (RS485, Modbus, Profibus)
42. How to Maintain a Pyrometer?
- Keep the lens clean and free from dust
- Ensure correct alignment and mounting
- Avoid moisture and vibration exposure
- Calibrate periodically using a reference source
43. How to Check if a Pyrometer is Working Properly?
- Compare its reading with a contact thermometer
- Test using a blackbody calibration source
- Check signal output using a multimeter or PLC
44. Can We Connect a Pyrometer to a PLC?
Yes, pyrometers with 4–20 mA or RS485/Modbus output can be directly connected to a PLC using analog or communication modules.
45. What is PID?
PID stands for Proportional-Integral-Derivative. It is a control algorithm used in automation to maintain a process variable (like temperature or pressure) at a desired setpoint.
46. What Are the Different Types of PID Controllers?
- Standalone PID controller
- PLC-integrated PID function block
- DCS-based PID loop
47. Why is PID Used in Automation?
PID provides continuous, real-time control of process variables and adjusts outputs to maintain stability and accuracy in automated systems.
48. How Does PID Work?
PID uses three terms:
- P (Proportional): Responds to current error
- I (Integral): Responds to accumulated past errors
- D (Derivative): Responds to rate of change of error
It calculates the output to minimize error over time.
49. Why is PID Preferred in Industry?
Because it offers:
- Fast and stable control
- Less overshoot and steady-state error
- Automatic compensation for disturbances
50. When Do We Use PID?
Use PID when precise control is required in:
- Temperature loops
- Pressure control
- Level regulation
- Flow control
51. What Type of Data is Required for PLC PID?
PID in PLC requires:
- Process Variable (PV): Measured value
- Setpoint (SP): Desired value
- Control Output (CO): Output to actuator (e.g., valve)
52. Where Do We Use PID?
PID is used in:
- Boilers
- Ovens
- Mixing tanks
- Compressor control
- Water level tanks
53. What is a PID Controller?
A PID controller is a device or software that automatically adjusts control outputs using PID logic to maintain the process variable near the setpoint.
54. Can We Make a PID Program in PLC?
Yes, most PLCs provide built-in PID instruction blocks which you can program to control loops like temperature, flow, or pressure.
55. What is the Difference Between PLC PID Instruction and External PID Controller?
| Aspect | PLC PID | External PID Controller |
|---|
| Integration | Direct in PLC logic | Separate hardware |
| Flexibility | More flexible programming | Limited options |
| Wiring | Minimal | Requires external wiring |
56. Which One is Preferred: External PID or PLC PID?
PLC PID is preferred for integrated automation systems, especially when multiple loops need control. External PID is useful for standalone or local control.
57. Can PID Help to Run Process Smoothly?
Yes, PID controllers ensure smoother operation by reducing fluctuation, minimizing error, and maintaining the setpoint, especially in dynamic processes.
58. What is a Switch?
A switch is an electrical device used to open or close a circuit. It can be mechanical, proximity-based, or digital.
59. What is an Emergency Switch?
An emergency switch (E-stop) is used to immediately stop machinery or a process during hazardous situations. It is a safety device.
60. What is a Momentary Push Button?
A momentary push button is a switch that only stays active while being pressed. Once released, it returns to its normal state.
61. What is a Limit Switch?
A limit switch is a mechanical switch used to detect the physical position or limit of a machine component (like actuator or conveyor end).
62. What is the Output of a Limit Switch?
Limit switches give a digital output — either ON or OFF (1 or 0) — based on mechanical position.
63. How to Maintain a Limit Switch?
- Keep the actuator lever or plunger clean
- Check for mechanical wear or sticking
- Verify the wiring and contact points
- Test function during shutdown checks
64. What is LVDT?
LVDT stands for Linear Variable Differential Transformer. It is an electromechanical sensor used to measure linear displacement or position. LVDT converts mechanical movement into an electrical signal and is commonly used in automation, aerospace, and testing equipment. It is highly accurate, reliable, and operates without physical contact, which increases its lifespan and stability.
65. What is the Working Principle of LVDT?
The LVDT has one primary coil and two secondary coils wound on a hollow cylindrical form. A movable magnetic core (made of soft iron) is placed inside the coil assembly and is connected to the object whose position is to be measured.
When an AC voltage is applied to the primary coil, it induces voltages in both secondary coils due to mutual induction. The difference in voltage between the two secondary coils is the output. When the core is in the center (null position), both secondary voltages are equal, and the output is zero. As the core moves, the voltage difference increases, indicating direction and distance of movement.
66. What are the Types of LVDT?
- AC LVDT: Uses AC excitation; suitable for industrial and high-precision applications.
- DC LVDT: Contains built-in electronics to work with DC; easier to interface but less rugged.
- Digital LVDT: Provides digital output using ADC circuits; used in modern control systems.
67. What is the Output of LVDT?
The output of an LVDT is an AC voltage that varies with the position of the core. After demodulation, it provides a DC voltage proportional to displacement. The output has:
- Amplitude: Proportional to how far the core moves.
- Phase: Indicates direction (left or right of the null position).
68. How to Connect LVDT to a PLC?
Since LVDTs produce analog voltage output, they are typically connected to a PLC via an analog input module. The steps are:
- Connect LVDT signal to an LVDT signal conditioner (to convert to 4–20 mA or 0–10 V).
- Connect signal conditioner output to the PLC's analog input channel.
- Scale the signal in the PLC program to convert voltage/current to engineering units (e.g., mm).
69. How to Maintain an LVDT?
To ensure long life and accurate measurement, the following maintenance practices should be followed:
- Keep the LVDT and its core clean and dust-free.
- Ensure no mechanical obstruction to core movement.
- Check cable connections and shielding for electrical noise issues.
- Calibrate the system periodically using known displacement references.
70. Where is LVDT Used?
LVDTs are used wherever precise linear displacement measurement is required. Common applications include:
- Industrial automation systems
- Material testing machines
- Robotics and servo positioning systems
- Aircraft control systems
- Turbine blade and valve position monitoring
71. What are the Applications of LVDT?
- Displacement and position sensing in mechanical systems
- Bridge and structural monitoring for civil engineering
- Hydraulic and pneumatic valve position control
- Automated inspection and quality control in factories
- Automotive crash testing and suspension systems
72. How to Troubleshoot an LVDT?
If the LVDT is not functioning properly, check the following points:
- No Output: Ensure the signal conditioner is powered and connected properly.
- Fluctuating Signal: May be due to poor shielding, electrical noise, or loose connections.
- Non-linear Output: Can result from a misaligned or stuck magnetic core.
- Incorrect Scaling: Verify scaling parameters in the PLC and signal converter settings.
73. What is RLT (Radar Level Transmitter)?
RLT stands for Radar Level Transmitter. It is a non-contact level measurement device that uses radar (microwave) signals to detect the level of liquids, solids, or slurries in a tank or vessel. RLTs are widely used in industries like oil & gas, water treatment, food & beverage, and chemicals due to their accuracy and reliability.
74. What is the Basic Principle of RLT?
RLT works on the principle of time-of-flight. It emits high-frequency radar waves toward the material surface. The waves reflect back to the transmitter, and the time taken for the signal to return is used to calculate the distance from the radar to the surface. This distance is then converted into level.
75. What Are the Types of Radar Level Transmitters?
- Non-contact (FMCW or Pulse Radar): Radar waves are sent through the air; used for most applications.
- Guided Wave Radar (GWR): Radar pulses travel through a probe/rod; ideal for high-pressure or dielectric materials.
76. What is the Output of an RLT?
Radar level transmitters typically provide an analog output of 4–20 mA proportional to the measured level. Some transmitters also support HART, Modbus, or Profibus for digital communication.
77. How to Install an RLT?
Steps for proper installation:
- Mount RLT vertically at the top of the tank using threaded or flange connections.
- Avoid installing near the tank wall, agitators, inlet nozzles, or ladders.
- Ensure the antenna is clean and not blocked by dust or foam.
- Use mounting guidelines from the manufacturer for best signal return.
78. What is the Basic Setup of an RLT?
After mechanical installation, perform the basic setup:
- Power up the RLT (usually 24 VDC supply).
- Configure parameters like tank height, empty and full calibration levels, dielectric constant, and output scaling.
- Use handheld HART communicator, Modbus device, or PC software to set parameters.
- Check live level reading and verify with actual measurement.
79. How to Wire an RLT?
Typical wiring involves:
- Connect 24V DC power supply to the transmitter terminals.
- Connect the analog output wires (4–20 mA loop) to the PLC analog input module.
- If using HART, connect a communicator across the loop for configuration.
- Follow proper grounding and shielding practices to prevent noise.
80. What Are the Wiring Standards for RLT?
Common wiring practices include:
- Use shielded twisted pair cable for analog signal lines.
- Follow IEC 61010-1 and ISA RP50.11 for installation safety.
- Route signal and power cables separately to avoid interference.
- Always use proper earth grounding for reliable measurements.
81. How to Maintain an RLT?
To ensure accuracy and longevity:
- Keep the antenna clean and free from buildup (especially in sticky or dusty materials).
- Verify mounting stability and vibration isolation.
- Check for condensation or moisture in electronics housing.
- Re-calibrate or validate readings periodically, especially after process changes.
82. What Are Common Troubleshooting Tips for RLT?
- No signal or level fluctuation: Check if the antenna is blocked, or material has low dielectric constant.
- Incorrect reading: Re-check empty and full calibration or dead zone settings.
- PLC not receiving signal: Check loop wiring and analog module configuration.
- Electrical noise: Use shielded cable and proper grounding.
83. Where Is RLT Used?
Radar level transmitters are used in:
- Oil and chemical storage tanks
- Food and beverage processing tanks
- Water and wastewater treatment plants
- Powder, granule, and slurry level detection in silos
- Pharmaceutical and hygienic applications (with hygienic design probes)
84. How to Troubleshoot a Radar Level Transmitter (RLT)?
If your radar level transmitter is not working properly, follow these steps to troubleshoot common issues:
- No Output Signal:
- Check power supply (usually 24V DC).
- Ensure correct loop wiring (check for open loop).
- Verify analog output range in settings (4–20 mA).
- Incorrect or Fluctuating Level Reading:
- Ensure antenna is clean and free from buildup or foam.
- Check if the material has a very low dielectric constant.
- Make sure the radar is mounted away from nozzle walls or agitators.
- Constant Full or Empty Level:
- Check calibration parameters (empty and full tank values).
- Verify dead zone configuration and tank height setting.
- Inspect for signal reflection issues due to tank geometry.
- Interference or Noise in Signal:
- Use shielded and grounded cables to prevent EMI.
- Keep signal wires away from high-voltage cables.
- Ensure proper grounding of transmitter housing.
- PLC Not Receiving 4–20 mA Signal:
- Check analog input configuration in PLC.
- Use a multimeter in series to verify loop current.
- Ensure polarity and terminal connections are correct.
Pro Tip: Most modern RLTs have a diagnostic function via HART communicator or configuration software. Use it to view live signal strength, echo curve, and device health.
85. What is an Ultrasonic Level Transmitter (ULT)?
An Ultrasonic Level Transmitter is a non-contact sensor that uses high-frequency sound waves to measure the level of a liquid or solid inside a tank. It calculates level based on the time taken for the ultrasonic pulse to travel to the material surface and reflect back.
86. What is the Working Principle of ULT?
ULT operates on the Time-of-Flight (ToF) principle. It emits an ultrasonic pulse toward the surface. The time it takes for the echo to return is used to calculate the distance, which is then subtracted from the tank height to determine the level.
87. What is the Output of ULT?
Ultrasonic transmitters typically provide:
- Analog output: 4–20 mA or 0–10 V
- Digital communication: Modbus, HART (optional)
88. What Are the Applications of Ultrasonic Level Transmitters?
- Water and wastewater level monitoring
- Chemical tank level measurement
- Open channel flow monitoring
- Solids like grain, powder, or sand level
89. How to Install ULT?
- Mount vertically at the top center of the tank
- Ensure a clear path for signal without obstacles (no agitators, pipes, etc.)
- Avoid foam or heavy vapor environments
- Follow manufacturer’s mounting height and angle guidelines
90. How to Wire ULT to PLC?
- Connect 24V DC to power terminals
- Connect analog output (4–20 mA) to the PLC analog input module
- Use shielded cable to avoid EMI
- If using Modbus, connect RS485 wires to PLC communication port
91. What is the Basic Setup of ULT?
- Power on and set tank height and span
- Calibrate using empty and full level
- Apply damping or filtering to smooth the signal
- Check live level value and verify it with manual dip reading
92. What Are the Types of Ultrasonic Level Sensors?
- Compact ULT: Integrated electronics and sensor
- Remote sensor: Sensor and display unit are separate
- Multichannel ULT: Monitors multiple tanks with one unit
93. How to Maintain ULT?
- Clean transducer face regularly
- Ensure no dust or cobwebs block the signal path
- Protect from moisture and vibration
- Check wiring and echo curve if signal is unstable
94. Where is Ultrasonic Level Transmitter Used?
- Sewage and water treatment tanks
- Acid and chemical level measurement
- Grain silos and cement bins
95. How to Troubleshoot Ultrasonic Level Transmitter?
- No output: Check power and loop connections
- False readings: Inspect for foam, vapor, or interference in beam path
- Fluctuating signal: Use echo curve diagnostics and apply filtering
- Incorrect scaling: Reconfigure empty and full calibration points
96. What is a Pressure Transmitter?
A Pressure Transmitter is an instrument that measures pressure in gases or liquids and converts it into an analog electrical signal (typically 4–20 mA). It is widely used in process industries for monitoring and control.
97. What is the Working Principle of a Pressure Transmitter?
It works on the principle of a strain gauge or piezoresistive effect. When pressure is applied to a diaphragm, it deforms and changes resistance, which is converted into an electrical signal proportional to the pressure.
98. What Are the Types of Pressure Transmitters?
- Gauge Pressure (G): Measures relative to atmospheric pressure
- Absolute Pressure (A): Measures from a perfect vacuum
- Differential Pressure (DP): Measures difference between two points
99. What is the Output of a Pressure Transmitter?
Most pressure transmitters give:
- Analog: 4–20 mA or 0–10 V
- Digital: HART, Modbus, or Profibus
100. What Are the Applications of Pressure Transmitters?
- Boiler and steam pressure monitoring
- Water, oil, and chemical pipeline pressure
- Tank level (using hydrostatic pressure)
- Pump and compressor control
101. How to Install a Pressure Transmitter?
- Mount vertically, facing the process line
- Use impulse lines for high-temperature or remote measurement
- Use sealing and thread tape to prevent leakage
- Mount at correct elevation for accurate hydrostatic level
102. How to Wire a Pressure Transmitter to PLC?
- Connect 24V DC supply to the transmitter terminals
- Connect the 4–20 mA output to the PLC’s analog input
- Ensure the loop is complete and grounded
- Use shielded twisted-pair cable for noise immunity
103. What is the Standard Setup of a Pressure Transmitter?
- Zero and span calibration using pressure source
- Configure range (e.g., 0–10 bar = 4–20 mA)
- Scale the signal in PLC to engineering units
104. How to Maintain a Pressure Transmitter?
- Inspect diaphragm for clogging or corrosion
- Check impulse lines for blockages or air pockets
- Verify calibration annually or as per standard
- Protect from mechanical vibration and water ingress
105. Where Are Pressure Transmitters Used?
- Oil refineries and chemical plants
- Food and beverage process lines
- HVAC and boiler systems
- Water distribution and sewage plants
106. How to Troubleshoot a Pressure Transmitter?
- No output: Check loop power and wiring
- Wrong reading: Calibrate transmitter with pressure calibrator
- Signal noise: Use shielded cable and check grounding
- Zero shift: Check for diaphragm damage or clogs