The NCS-TT306H is a high-accuracy, low-drift, high-reliability HART 7 temperature transmitter built for process control. It accepts a wide range of RTD, thermocouple, resistance, and millivolt sensors, outputs 4–20 mA with HART superimposed, and adds three things that matter on critical loops: an optional SIL safety mode, dual-channel hot-backup redundancy, and sensor-drift and corrosion diagnostics.
The series comes in two form factors — the head-mount NCS-TT306H and the DIN-rail NCS-TT306H-R — and in single- or dual-channel versions.
Why It Stands Out
Functional safety (SIL mode). The transmitter can be switched into a dedicated SIL mode via an access code. On entry it runs a checksum verification and a self-diagnostic, and only enters SIL mode if both pass. In SIL mode the configuration is locked, diagnostic alarm levels switch to a fixed preset set, and the device can be forced to a safe state. A SIL configuration timestamp is recorded by the user for audit purposes. This is the model to specify when the temperature loop is part of a safety instrumented function.
Dual-channel hot backup. On a dual-channel unit, sensor 1 and sensor 2 back each other up. If the PV is mapped to sensor 1 and sensor 1 fails open or short, the transmitter automatically switches the PV and the loop current to sensor 2 — and switches back when sensor 1 recovers. For a critical measurement point, this removes the single sensor as a single point of failure without adding a second transmitter.
Sensor diagnostics. Beyond open/short detection, the dual-channel version offers sensor-drift detection (compares the two channels against a configurable set point, in window-in or window-out mode) and corrosion detection (monitors lead resistance against a configurable limit). These turn a silent sensor degradation into an actionable alarm.
Sensor Support
A single NCS-TT306H accepts an unusually wide sensor set:
- RTDs: Pt100, Pt100_GOST, Pt50_GOST, Pt200, Pt500, Pt1000, Cu50, Cu50_GOST, Cu100, Cu100_GOST, Ni50, Ni100, Ni120, Ni1000, and Callendar–Van Dusen (PT100)
- Resistance: 0–500 Ω, 0–2000 Ω, 0–4000 Ω, 0–40000 Ω
- Thermocouples: B, E, J, K, N, R, S, T, L_GOST, A (W5Re/W20Re), C (W5Re/W26Re), D (W3Re/W25Re), NiCrAuFe, CuAuFe
- Millivolt: −100 mV to +100 mV
RTDs and resistance signals on sensor 1 support 2-, 3-, and 4-wire connection; sensor 2 (dual-channel) supports 2- and 3-wire. Thermocouple cold-junction compensation can be set to internal, external (an external Pt100), a fixed value, or — on dual-channel units — measured by sensor 2.
Measurement Accuracy
All figures referenced at 25 °C.
RTD and resistance (selected):
| Sensor | Range | Accuracy (25 °C) | Drift (per °C) |
|---|---|---|---|
| Pt100 | −200 to 850 °C | ±0.10 °C | ±0.003 °C |
| Pt1000 | −200 to 850 °C | ±0.10 °C | ±0.005 °C |
| Cu100 | −50 to 150 °C | ±0.10 °C | ±0.003 °C |
| Ni100 | −60 to 180 °C | ±0.10 °C | ±0.002 °C |
| 0–500 Ω | — | ±0.04 Ω | ±0.001 Ω |
| 0–4000 Ω | — | ±0.35 Ω | ±0.015 Ω |
Thermocouple (selected):
| Type | Range | Accuracy (25 °C) | Drift (per °C) |
|---|---|---|---|
| E | −200 to 1000 °C | ±0.20 °C | ±0.025 °C |
| J | −190 to 1200 °C | ±0.35 °C | ±0.010 °C |
| K | −200 to 1372 °C | ±0.40 °C | ±0.025 °C |
| T | −200 to 400 °C | ±0.35 °C | ±0.015 °C |
| B | 500 to 1810 °C | ±0.77 °C | ±0.050 °C |
Cold-junction compensation accuracy is ±0.5 °C with an external Pt100, or ±1.0 °C with internal compensation. The millivolt input measures to ±0.025 mV. Common-mode and series-mode rejection are both ≥70 dB at 50 Hz and 60 Hz.
Configuration and Output
The transmitter is configured with Microcyber’s HartMPT software, FieldComm Group’s FDI, or other general HART tools, over a HART modem with a 230–550 Ω loop resistance. Configurable items include device tags and address, PV range and damping (0–32 s), engineering unit (°C, °F, °R, K, mV, Ω), sensor type and wiring, multi-point linearization (up to 16 points), HART burst, diagnostics, and SIL.
Output behaviour follows standard practice. The PV at 20 mA sets the upper range, the PV at 4 mA the lower range. Alarm current is configurable — high alarm 21.00–23.00 mA (default 21.75 mA), low alarm 3.50–3.70 mA (default 3.60 mA) — with saturation limits of 20.0–20.8 mA high and 3.75–4.0 mA low. On over-range the output drives to 20.8 mA above range and 3.8 mA below. In multidrop, HART 7 supports up to 64 devices (polling addresses 0–63).
Head-mount units optionally include an LCD with three local keys (M / S / Z) for on-site configuration of sensor type, unit, wiring, and range without a host tool. The rail-mount NCS-TT306H-R has no display.
Key Specifications
| Parameter | Value |
|---|---|
| Bus interface | 4–20 mA (current reversal supported) + HART 7 (Burst supported) |
| Bus power | 10–45 VDC / 10–30 VDC (intrinsic safety / SIL); 13–45 VDC / 13–30 VDC with LCD |
| Protocol | HART 7 |
| Channels | Single or dual |
| Wiring | 2-, 3-, or 4-wire |
| Input impedance | ≥10 MΩ |
| Electrical isolation | 1.5 kVAC / 42 VAC |
| Voltage effect | ±0.005 %/V |
| Current accuracy | 0.05%; drift 0.005 %/°C |
| Operating temperature | −40 (−55) °C to 85 °C (no display); −20 to 70 °C (with display) |
| Humidity | 5% to 95% RH |
| Storage temperature | −40 to 85 °C |
| Start-up time | ≤10 s |
| Update time | 0.8 to 1.3 s |
| Vibration | 2–25 Hz: ±1.6 mm; 25–100 Hz: ±4 g |
| Protection | Terminal IP00, module housing IP20, rail housing IP20 |
| Weight | Module ≤75 g; display card ≤50 g; rail ≤100 g |
| Dimensions | NCS-TT306H: ⌀45 × 23 mm; NCS-TT306H-R: 110 × 99 × 22.5 mm |
| Housing material | Polycarbonate |
Ordering
The NCS-TT306 model code specifies, in order: protocol (H = HART); mounting (H = dual-channel head, H1 = single-channel head, R = dual-channel rail, R1 = single-channel rail); explosion protection (IC = intrinsically safe, NA = non-explosion-proof); LCD (C = with LCD, N = no LCD); housing material (C2 = SUS 316, C3 = SUS 304, C4 = cast aluminium); connector thread (E1 = ½ NPT, E2 = M20); and other certification (SL = SIL).
Applications
The NCS-TT306H is used for temperature measurement in petroleum, chemicals, power generation, and metallurgy — and, with its SIL mode and hot-backup redundancy, on temperature loops that carry a safety or availability requirement.