In the world of instrumentation and control, the pressure transmitter plays a critical role in ensuring accurate and reliable process measurements. Whether you’re designing, selecting, or maintaining instrumentation systems, understanding the pressure transmitter datasheet is essential. However, many engineers and technicians find these datasheets dense or difficult to interpret, often overlooking critical parameters that can impact performance, reliability, and safety.
This blog aims to demystify the pressure transmitter datasheet by breaking down each section, explaining its purpose, and offering practical insights into how the information can be used in real-world applications.
- Introduction to Pressure Transmitters
A pressure transmitter converts pressure into an electrical signal that can be read by control systems. It is used to measure:
- Gauge Pressure (PG)
- Absolute Pressure (PA)
- Differential Pressure (DP)
- Vacuum or Compound Pressure
Pressure transmitters are vital in refineries, petrochemical plants, water treatment facilities, and various process industries.
- Purpose of the Datasheet
A datasheet is a technical document that details the specifications, features, materials, and limitations of the pressure transmitter. It serves as a reference for:
- Instrument Selection
- System Integration
- Installation Planning
- Maintenance and Troubleshooting
- Key Sections of a Pressure Transmitter Datasheet
Let’s decode the datasheet section by section:
3.1 Tag Number / Instrument Identification
- Example: PT-101
- Purpose: Unique identifier for the transmitter based on P&ID, location, or loop number.
- Insight: Ensure it matches your project documentation (loop diagrams, P&IDs, IO lists).
3.2 Service Description / Process Description
- Example: Crude Oil Line – Suction Pressure Measurement
- Purpose: Describes the application environment and function.
- Insight: Helps determine material compatibility and accuracy requirements.
3.3 Measured Variable
- Example: Pressure (Gauge), Pressure (Absolute), Differential Pressure
- Purpose: Clarifies what the transmitter is intended to measure.
- Insight: Selection of sensor technology and calibration depends on this.
3.4 Process Conditions
| Parameter | Typical Values |
| Process Pressure | 0 to 100 barg |
| Operating Temperature | 40°C to 120°C |
| Design Pressure | 150 barg |
| Fluid Type | Hydrocarbon / Steam / Water |
- Insight: Process pressure and temperature impact sensor range, material selection, and enclosure rating.
3.5 Range and Span
- Example:
- LRV (Lower Range Value): 0 barg
- URV (Upper Range Value): 100 barg
- Span: URV – LRV = 100 barg
- Insight:
- Select a transmitter whose turndown ratio supports your range.
- Too wide a range may reduce accuracy; too narrow may cause over-range failure.
3.6 Output Signal
- Example: 4-20 mA with HART
- Other Options: FOUNDATION Fieldbus, PROFIBUS, 1-5V
- Insight: Choose based on your control system compatibility. HART is most common for diagnostics and configuration.
3.7 Power Supply
- Typical: 12–42 VDC (usually 24 VDC)
- Insight: Ensure your loop power supply matches transmitter requirement. Check for minimum voltage considering cable length and load resistance.
3.8 Accuracy
- Example: ±0.1% of span
- Insight:
- Higher accuracy needed in custody transfer or billing applications.
- For general process control, 0.25% or 0.5% is acceptable.
3.9 Sensor Type / Technology
- Examples: Capacitive, Piezoresistive, Strain Gauge
- Insight: Determines performance in harsh environments (temperature drift, overpressure tolerance, etc.)
3.10 Response Time
- Example: < 200 ms
- Insight:
- Fast response required for control loops.
- Damping may be added to avoid signal noise in fluctuating applications.
3.11 Overpressure Limit
- Example: 2× Full Scale (FS)
- Insight: Ensure that process upsets will not damage the sensor. Critical for surge-prone systems.
3.12 Process Connection
- Example: 1/2” NPT (M), Flanged (ANSI/ASME), DIN, Tri-Clamp
- Insight:
- Must match with process nozzle.
- Sanitary applications require hygienic fittings like Tri-Clamp.
- Consider diaphragm seal if fluid is viscous or corrosive.
3.13 Material of Wetted Parts
- Examples: SS316, Hastelloy C, Monel, Tantalum
- Insight:
- Must be compatible with process fluid to avoid corrosion.
- Use corrosion charts or consult process chemist if in doubt.
3.14 Diaphragm Seal / Remote Seal
- Required for:
- High temperature
- Corrosive service
- Hygienic applications
- Insight:
- Use filled capillaries or direct mount.
- Check fill fluid compatibility and ambient limits.
3.15 Enclosure Material & Rating
- Material: Aluminum, SS316
- Ingress Protection: IP66 / IP67 / NEMA 4X
- Hazardous Area Certification: Ex d, Ex i, Ex e
- Insight:
- Aluminum is lightweight; SS preferred in corrosive offshore or marine environments.
- Match certification with hazardous area classification zone.
3.16 Electrical Connection
- Examples: 1/2” NPT conduit, M20, Cable Gland, Terminal Block
- Insight: Select based on field cable termination style. Proper sealing prevents moisture ingress.
3.17 Mounting Type
- Options:
- Direct Mount
- Bracket Mount (2″ pipe)
- Panel Mount
- Insight: Use manifold or bracket to isolate, vent, and calibrate. Check for proper orientation (vertical or horizontal).
3.18 Accessories
- Manifold Valve (2/3/5 way)
- Surge Protector
- Drip Ring / Condensate Pot
- Vent Plug
- Thermal Insulation
- Insight:
- Accessory selection depends on process conditions and calibration needs.
3.19 Calibration Certificate
- Factory Calibrated to specified LRV/URV
- Insight: Ensure traceability to national/international standards. Keep certificates for validation/audit purposes.
3.20 Vendor and Model
- Example: Rosemount 3051, Yokogawa EJA110E, ABB 266, Siemens Sitrans P
- Insight: Compare based on availability, cost, diagnostics, and reliability.
- Real-World Application: Oil & Gas Case Study
Project: Offshore Platform
- Service: HP Separator Pressure Monitoring
- Process Fluid: Sour Gas (H₂S > 500 ppm)
- Requirement:
- Diaphragm seal with capillary
- Material: Hastelloy C wetted parts
- Range: 0–100 barg
- Output: 4–20 mA + HART
- Hazardous Area: Zone 1, Gas Group IIB, T4
- Selected Transmitter: Yokogawa EJA530E with remote seal and Ex d flameproof housing
Why It Matters: The wrong selection (e.g., SS316 in sour service) would have resulted in corrosion failure, risking safety and downtime.
- Tips for Interpreting and Using Datasheets Effectively
| Tip | Description |
| Always match with process data | Don’t assume default ranges or materials. Customize for every application. |
| Check certifications | ATEX, IECEx, PESO, SIL – ensure compliance. |
| Request GA drawings | Helps during installation planning. |
| Confirm fill fluid details | Especially important in diaphragm seal transmitters. |
| Use manufacturer selection tools | Vendors like Emerson, Yokogawa, and ABB provide online configurators. |
| Don’t ignore small details | An incorrect electrical entry or thread size can delay commissioning. |
- Conclusion
The pressure transmitter datasheet is more than a formality—it’s a technical blueprint that can determine the success or failure of your measurement system. By carefully decoding each parameter, you ensure accurate measurement, operational safety, and long-term reliability.
As an instrumentation professional, being able to interpret, review, and verify datasheets will set you apart and make your project execution smoother. Take your time with datasheets—your plant’s performance depends on it!
- Downloadable Checklist (Optional)
Here’s a brief checklist to review while decoding a pressure transmitter datasheet:
✅ Tag Number
✅ Measurement Type (Gauge/Absolute/DP)
✅ Process Conditions (Pressure, Temp, Fluid)
✅ Range and Accuracy
✅ Output Signal
✅ Overpressure Limits
✅ Material of Wetted Parts
✅ Hazardous Area Certification
✅ Diaphragm Seal Requirement
✅ Electrical and Process Connection
✅ Calibration and Accessories