1. Model Selection Check

Before installing any pressure transmitter, verify that the model matches your process requirements. The NCS-PT105 series is available in four pressure types and three communication protocols. Selecting the wrong model is the single most common root cause of commissioning delays.

1.1 Pressure Type Selection

Model	Pressure Type	Typical Application
NCS-PT105ⅡSG	Gauge pressure	Tank level, pipe pressure, general process
NCS-PT105ⅡSA	Absolute pressure	Vacuum process, barometric measurement
NCS-PT105ⅡSD	Differential pressure	Flow measurement (orifice plate), filter DP, level in closed vessels
NCS-PT105ⅡSH	High static DP	High-line-pressure flow measurement, reactor level

1.2 Communication Protocol Selection

Model Suffix	Protocol	Key Consideration
NCS-PT105ⅡH	HART 7 (4–20 mA)	Compatible with existing analog loops; simplest upgrade path
NCS-PT105ⅡF	FOUNDATION Fieldbus H1	ITK 6 certified; for digital control systems with FF infrastructure
NCS-PT105ⅡP	PROFIBUS PA	Profile 3.02; for Siemens/DCS systems with PA segments

Check the nameplate on the transmitter housing before installation. The model code, pressure range, and explosion-proof rating are printed there. If any parameter does not match your P&ID / instrument datasheet, stop and escalate before proceeding.

2. Mechanical Installation

2.1 Location Selection

Measurement accuracy depends heavily on where you install the transmitter. Follow these rules:

• Install as close to the process tap as practical — shorter impulse lines mean faster response and less chance of trapped gas or liquid.
• Avoid locations with severe vibration (pump discharge, compressor outlet). If unavoidable, use a support bracket within 300 mm of the transmitter.
• Keep the transmitter accessible for calibration and maintenance. Maintain at least 500 mm clearance around the housing.
• For outdoor installations, use a weather shield or install under a canopy. The NCS-PT105 is rated IP67, but prolonged UV and rain exposure degrades the housing over time.

2.2 Orientation by Medium Type

The impulse line routing differs depending on the process medium:

Medium	Tap Location	Transmitter Position	Rationale
Liquid	Side of pipe	Below the tap	Gas in impulse line drains back into process
Steam	Side of pipe	Below the tap	Condensate fills impulse line, isolating transmitter from high temperature
Gas (dry)	Top or side of pipe	Above the tap	Condensate drains back into process; prevents liquid accumulation in impulse line

Important: For differential pressure transmitters on steam service, fill both impulse legs with condensate before opening the root valves. Unequal fill causes a zero shift that can exceed the transmitter’s accuracy specification.

2.3 Mounting

The NCS-PT105 ships with three bracket options:

1. Pipe-mount flat bracket — vertical pipe Φ50 mm, U-bolt included.
2. Pipe-mount angle bracket — horizontal pipe Φ50 mm, U-bolt included.
3. Plate-mount angle bracket — flat surface, M10 bolt.

Torque the transmitter-to-bracket bolts to 8–12 N·m. Over-tightening cracks the housing; under-tightening allows vibration loosening.

3. Electrical Installation

3.1 Power Supply & Loop Wiring (HART)

The HART version shares power and signal on one pair of cables. Key requirements:

Parameter	Non-IS Version	IS Version (Ex ia)
Supply voltage	11.9–42 VDC	11.9–30 VDC
Load resistance	250 Ω (required for HART comm.)	250 Ω (required for HART comm.)
Max loop resistance	(Vsupply − 11.9) / 0.022 A	(Vsupply − 11.9) / 0.022 A
Cable type	Shielded twisted pair, 22 AWG typical	Shielded twisted pair, must match IS barrier specs

Voltage Drop Example

A 24 VDC power supply with 250 Ω loop resistor and 200 m of 22 AWG cable (56 Ω/km round-trip):

• Cable resistance = 200 m × 2 × 56 Ω/km = 22.4 Ω
• Voltage at transmitter = 24 V − (0.022 A × (250 + 22.4) Ω) = 24 − 6.0 = 18.0 V → above 11.9 V minimum ✓

3.2 FF H1 & PROFIBUS PA Wiring

For FF and PA versions, use IEC 61158-2 compliant fieldbus cable (Type A preferred). Key differences from HART:

• FF H1 supply voltage: 9–32 VDC (non-IS) / 9–17.5 VDC (IS).
• PA supply voltage: 9–32 VDC (non-IS) / 9–17.5 VDC (IS).
• No 250 Ω resistor is needed — the DCS / segment coupler provides the termination.
• Spur length per device: up to 120 m (FF) or per PA profile design guideline.

3.3 Shielding & Grounding

• Ground the shield at one point only — typically at the DCS / control room end.
• Do not run fieldbus cables in the same conduit as power cables or high-frequency signal lines.
• The transmitter housing must be grounded to the plant ground grid. Use the external grounding screw on the housing.

3.4 Terminal Wiring

Remove the rear cover to access the terminal board (marked “FIELD TERMINAL”). For HART:

• Signal “+” → left terminal
• Signal “−” → center terminal (shared with test −)
• Test “+” → right terminal (HART only, for test instrument)

Warning: Do NOT connect the signal wires to the test terminals — this will damage the internal diodes. If diodes are already damaged, the emergency workaround is to short the two test terminals together.

4. Factory Acceptance Testing (FAT)

4.1 Hydrostatic Test (Pressure Hold)

• Apply 1.5× the rated working pressure (or per ASME B31.3 / project spec) and hold for 15–30 minutes.
• Monitor for any pressure decay indicating a leak at the process connection, impulse line fittings, or transmitter flange.
• The NCS-PT105 sensor itself is not user-serviceable; if the transmitter leaks from the sensor body, reject and replace.

4.2 PMI (Positive Material Identification)

• Verify the wetted parts material matches the instrument datasheet. Standard: 316L stainless steel.
• For corrosive service (H₂S, Cl⁻), confirm the optional Hastelloy C-276 diaphragm is installed.
• Use a handheld XRF analyzer. Document the alloy result on the FAT certificate.

4.3 DP Verification (Differential Pressure Transmitters Only)

• Apply known pressures to the high and low sides simultaneously using a dual-pressure calibrator.
• Verify zero output (4.000 mA) with equal pressure on both sides.
• Apply full span DP and verify 20.000 mA output. Tolerance: ±0.075% FS (standard) or ±0.05% FS (high-accuracy option).

5. HART Calibration Procedure

5.1 Equipment Required

• HART communicator (e.g., Emerson 475 / AMS Trex) or HART modem with DD software
• Pressure calibrator with accuracy ≤ 1/4 of transmitter accuracy (i.e., ≤ 0.019% FS for standard unit)
• 24 VDC loop power supply (or use the communicator’s built-in supply)
• 250 Ω resistor in the loop (if not built into the communicator)

5.2 Zero Trim

Perform a zero trim after mechanical installation to compensate for static head effects:

1. Equalize the process (vent both sides to atmosphere for DP, or zero gauge pressure for GP/AP).
2. Connect the HART communicator and navigate to Trim → Zero Trim.
3. Execute the trim. The transmitter adjusts its 4.000 mA point to the current applied pressure.
4. Verify: the output should read 4.000 mA ± 0.01 mA after trim.

Note: Zero trim range is limited to ±3.75% of URL. If the zero offset exceeds this, the process connection or impulse line is the likely cause — do not force the trim.

5.3 Span Calibration (Full Two-Point)

1. Apply zero pressure. Perform Zero Trim as above.
2. Apply full-span pressure (100% of calibrated range).
3. Navigate to Trim → Span Trim (or Sensor Trim → Upper Trim depending on DD version).
4. Enter the applied pressure value from the calibrator and confirm.
5. Verify: output should read 20.000 mA ± 0.01 mA.
6. Perform a 5-point linearity check (0%, 25%, 50%, 75%, 100% of span). Each point should be within ±0.075% FS.

5.4 Damping Configuration

The NCS-PT105 default damping is 0 seconds. Adjust only if process noise causes loop instability:

• Typical damping: 0.5–2.0 s for flow measurement (orifice plate noise).
• Keep damping at 0 s for pressure and level — these applications rarely need it.
• Range: 0–32 s configurable via HART. Do not set above 5 s unless the control loop response time explicitly allows it.

5.5 Calibration Interval Recommendation

The NCS-PT105 specification states ±0.2% of URL per 5 years annual stability. This means a transmitter rated for 1 MPa can drift up to ±2 kPa over a five-year period without any adjustment. Whether that drift matters depends on your process tolerances.

How to determine your interval:

1. Check your process tolerance first. If your loop tolerance is ±1.0% and the transmitter accuracy is 0.075% FS, you have enough headroom to run longer between calibrations.
2. Check the operating environment. High temperatures (+85°C operating ambient), vibration, or corrosive atmospheres accelerate drift. The NCS-PT105 operates up to +85°C non-explosion-proof, but derate to −30~60°C for Ex ia versions — exceeding these limits shortens the service life.
3. Check your site compliance requirements. Custody transfer and safety instrumented systems (SIS) have mandated intervals regardless of the stability spec.

How to verify without pulling the transmitter:

• Online verification: Compare the HART digital output (PV) against a calibrated reference gauge at two points (typically 0% and 100% of span). If both points are within your process tolerance, defer the full calibration.
• Partial calibration: If only zero drift is observed (common with installation elevation), a zero trim alone may restore accuracy without a full two-point calibration. This takes 15 minutes on site.

Warning: Document every calibration. Most compliance audits (ISO 9001, API, FDA) require:

• Date of calibration
• Technician name
• Equipment used (calibrator serial number, calibration due date)
• Before/after readings
• Pass/fail determination against your process tolerance, not just the transmitter spec

6. Common Failure Modes and Diagnosis

Symptom	Likely Cause	Diagnostic Action
Output stuck at 4 mA	No loop power or reversed polarity	Check voltage at transmitter terminals — must be >=11.9 VDC
Output stuck at 20.5 mA	Sensor overrange or diaphragm damage	Verify process pressure is within rated span; inspect diaphragm for deformation
Output noisy / fluctuating	Electrical noise, vibration, or grounding issue	Check single-point grounding; verify shield only at host end; measure AC noise (<25 mVpp)
HART communication fails	Missing 250 ohm loop resistor or IS barrier filtering HART	Measure resistance at communicator connection — must be 250 ohm +/-1%; check barrier pass-band
Slow response / damping	Damping time constant set too high	Check damping setting via HART communicator — default is 0s, configurable 0-32s
Span drift after 2+ years	Fill fluid degradation or diaphragm fatigue	Perform two-point calibration; if drift exceeds +/-0.2% URL, replace sensor module
Output at 3.6 mA alarm	Process alarm or sensor failure	Read HART status byte via communicator; check for sensor fault diagnostics
Zero drift after installation	Installation elevation or impulse line blockage	Perform zero trim if within +/-3.75% URL; otherwise check impulse line and venting

7. Technical Specifications Summary

7.1 NCS-PT105 4-20 mA + HART

Specification	Value
Output	4-20 mA + HART 7, Burst mode supported
Supply voltage (non-IS)	11.9-42 VDC
Supply voltage (IS)	11.9-30 VDC
Accuracy	0.075% FS (optional 0.05% FS)
Current accuracy	0.03%
Temperature drift (current)	50 ppm/degreeC
Annual stability	+/-0.2% URL / 5 years
Dielectric strength	500 VAC
Measurement range	Liquid, gas, steam
Medium temperature	-40~120 degreeC (silicone oil fill)
Start-up time	<=8 s
Refresh rate	50 ms
Damping time constant	0-32 s (configurable)
Explosion protection	Ex d IIC T6 Ga (DA) / Ex d IIC T4 Ga (DC) / Ex ia IIC T4 Ga (IC)
Display	LCD with magnetic bar operation
Operating temp (non-Ex, no display)	-40~85 degreeC
Operating temp (Ex ia T4 Ga, with display)	-30~60 degreeC
Humidity	5~95% RH
Storage temperature	-50~85 degreeC
Impact resistance	IK07 = 2 J
Protection rating	IP67
Weight	~3.6 kg

7.2 NCS-PT105 FOUNDATION Fieldbus H1

Specification	Value
Protocol	FOUNDATION Fieldbus H1, ITK 6
Supply voltage (non-IS)	9-32 VDC
Supply voltage (IS)	9-17.5 VDC
Accuracy	0.075% FS
Annual stability	+/-0.2% URL / 5 years
Start-up time	<=13 s
Explosion protection	Ex d IIC T6/T4 Ga / Ex ia IIC T4 Ga

7.3 NCS-PT105 PROFIBUS PA

Specification	Value
Protocol	PROFIBUS PA, Profile 3.02
Supply voltage (non-IS)	9-32 VDC
Supply voltage (IS)	9-17.5 VDC
Accuracy	0.075% FS
Annual stability	+/-0.2% URL / 5 years
Start-up time	<=12 s
Explosion protection	Ex d IIC T6/T4 Ga / Ex ia IIC T4 Ga