This article explains commonly used instrumentation abbreviations, definitions, symbols, nomenclature, and acronyms used in industrial control and measurement systems.
The table below highlights various symbols commonly used in industrial automation systems and instrumentation.
| Symbol | Description | Use / Meaning |
|---|---|---|
| A | Analog Signal | Represents a continuous signal such as 4–20 mA |
| AC | Analysis Controller | Controls analyzer-related parameters |
| AAH | Analysis Alarm (High) | Alarm activates when analysis value exceeds high limit |
| AAHL | Analysis Alarm (High/Low) | Alarm for both high and low abnormal analysis values |
| AAL | Analysis Alarm (Low) | Alarm when analysis value drops below low limit |
| AS | Air Supply | Indicates pneumatic air supply |
| ASDH | Analysis Shutdown (High) | Shutdown triggered at high analysis value |
| ASDL | Analysis Shutdown (Low) | Shutdown triggered at low analysis value |
| ASH | Analysis Switch (High) | Switch activates at high analysis value |
| ASHL | Analysis Switch (High/Low) | Switch for both high and low conditions |
| ASL | Analysis Switch (Low) | Switch activates at low analysis value |
| AT | Analysis Transmitter | Measures and transmits analyzer signals |
| BC | Burner Controller | Controls burner operation |
| BAH | Burner Alarm (High) | Alarm for high burner parameter |
| BAHL | Burner Alarm (High/Low) | Burner alarm for high and low limits |
| BAL | Burner Alarm (Low) | Alarm for low burner parameter |
| BDV | Blowdown Valve | Used for depressurizing or draining lines |
| BPR | Back Pressure Regulator | Maintains upstream pressure |
| BS | Burner Switch | Manual or automatic burner switching |
| BSH | Burner Switch (High) | Switch activates at high condition |
| BSHL | Burner Switch (High/Low) | Burner switching for high/low limits |
| BSL | Burner Switch (Low) | Switch activates at low condition |
| BS&W | Basic Sediment and Water | Indicates impurities in oil |
| CCP | Central Control Panel | Main control and monitoring panel |
| CDS | Compressor Shutdown | Shuts down compressor during fault |
| CFA | Common Fault Alarm | Indicates general system fault |
| COR | Corrosimeter | Measures corrosion rate |
| CSC | Car Seal Close | Valve locked in closed position |
| CSO | Car Seal Open | Valve locked in open position |
| CV | Control Valve | Regulates process variable |
| E/I | EMF to Current Converter | Converts voltage to current signal |
| ES | Electrical Switch | Electrical switching device |
| ESD | Emergency Shutdown Station | Manual emergency shutdown |
| ESDV | Emergency Shutdown Valve | Valve closes during emergency |
| FAL | Flow Alarm (Low) | Alarm for low flow condition |
| FAH | Flow Alarm (High) | Alarm for high flow condition |
| FC | Flow Controller / Fail Close | Controls flow or valve closes on failure |
| FCV | Flow Control Valve | Controls flow rate |
| FE | Flow Element | Primary flow-sensing device |
| FI | Flow Indicator | Displays flow value |
| FIC | Flow Indicator Controller | Indicates and controls flow |
| FIT | Flow Indicator Transmitter | Indicates and transmits flow |
| FO | Fail Open | Valve opens on failure |
| FS | Flow Switch | Detects flow presence |
| FT | Flow Transmitter | Measures and transmits flow |
| GS | Instrument Gas Supply | Gas supply for instruments |
| H | Hydraulic | Indicates hydraulic system |
| HOA | Hand/Off/Auto Switch | Mode selection switch |
| HS | Hand Switch | Manual switching |
| I | Current Signal | Electrical current signal |
| I/P | Current to Pneumatic | Converts current to air pressure |
| LA | Level Alarm | Alarm for abnormal level |
| LC | Level Controller | Controls liquid level |
| LCV | Level Control Valve | Regulates level |
| LG | Level Gauge | Visual level indication |
| LI | Level Indicator | Indicates level |
| LIT | Level Indicator Transmitter | Measures and transmits level |
| LS | Level Switch | Switch based on level |
| MCC | Motor Control Center | Controls electric motors |
| NC | Normally Closed | Contact closed in normal state |
| NO | Normally Open | Contact open in normal state |
| PAH | Pressure Alarm (High) | Alarm for high pressure |
| PC | Pressure Controller | Controls pressure |
| PCV | Pressure Control Valve | Regulates pressure |
| PG | Pressure Gauge | Indicates pressure locally |
| PI | Pressure Indicator | Displays pressure |
| PIT | Pressure Indicator Transmitter | Measures and transmits pressure |
| PSV | Pressure Safety Valve | Protects against overpressure |
| PT | Pressure Transmitter | Measures and transmits pressure |
| RTD | Resistance Temperature Detector | Measures temperature |
| RTU | Remote Terminal Unit | Remote data acquisition |
| TC | Temperature Controller | Controls temperature |
| TI | Temperature Indicator | Displays temperature |
| TIT | Temperature Indicator Transmitter | Measures and transmits temperature |
| TT | Temperature Transmitter | Transmits temperature signal |
| TW | Thermowell | Protects temperature sensor |
| VAH | Vibration Alarm (High) | Alarm for excessive vibration |
| VSH | Vibration Switch (High) | Switch activates on high vibration |
| WS | Water Supply | Water utility line |
| ZC | Position Switch (Closed) | Indicates valve closed |
| ZO | Position Switch (Open) | Indicates valve open |
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