A rail-mounted temperature transmitter can reduce cabinet space, support multiple sensor inputs, and simplify maintenance compared with head-mounted designs.
But not all rail-mounted transmitters are built the same.
This article explains how dual-channel rail-mounted temperature transmitters work, what accuracy specifications actually mean, and when a device such as the NCS-TT106H-R makes sense in a real instrumentation project.
Why mount a temperature transmitter on a DIN rail
A head-mount transmitter sits inside the sensor’s connection head, out in the field. A DIN rail transmitter sits in the control cabinet instead. That relocation changes a few practical things.
The electronics live in a temperature- and vibration-controlled enclosure rather than next to a hot process connection. Wiring terminates at a single point you can reach without going to the field. And when one device handles more than one sensor, you reduce the number of modules competing for rail space.
The trade-off is that the sensor-to-transmitter run is longer, which is why lead-wire compensation and signal isolation matter more in a rail-mount design. Both points come up in the specifications below.
Dual-channel input: what two channels actually buys you
The NCS-TT106H-R accepts two sensor inputs. Channel 1 can take up to a 4-wire RTD; channel 2 can take up to a 3-wire RTD. Both channels can also take a thermocouple signal at the same time.
That flexibility has limits worth reading before you design the wiring. The manual specifies which input combinations are valid across the two channels. A 4-wire RTD, for example, occupies enough terminals that it constrains what the second channel can do. Before committing a dual-sensor scheme, check the combination matrix in the manual rather than assuming any two input types can coexist.
Two inputs on one device support a few common patterns: measuring two nearby points with one module, or using the second sensor for cold-junction compensation. On this transmitter the thermocouple cold-junction compensation accuracy is ±0.5 °C using the internal measurement, and ±0.15 °C when a Pt100 on sensor 2 does the measurement. If you need the tighter figure, that second channel is doing real work, not sitting idle.
One point on terminology: dual-channel input raises measurement coverage and wiring density. It is not, by itself, a redundancy or availability feature. The output is a single 2-wire 4–20 mA / HART signal. If your safety or availability case needs redundancy, that is a separate architectural decision, not something a second input channel provides.
Supported sensors and ranges
The transmitter handles the common industrial RTD and thermocouple types.
| Sensor type | Compatible |
|---|---|
| RTD | Pt100, Pt1000, Cu50, Cu100 |
| Resistance | 0–500 Ω, 0–4000 Ω |
| Termopar | B, E, J, N, K, R, S, T |
| Voltage | −100 mV a +100 mV |
RTD wiring supports 2-wire, 3-wire, and 4-wire connection. The 4-wire mode is the one to use when accuracy matters, for the reason in the next section.
Accuracy figures, and the condition attached to them
Accuracy claims on a transmitter are only meaningful with their test conditions. Here are the manufacturer’s figures at 25 °C.
RTD accuracy:
| Signal | Recommended range | Precisión (25 °C) | Temperature drift (/°C) |
|---|---|---|---|
| Resistance | 0–500 Ω | ±0,04 Ω | ±0.001 Ω |
| Resistance | 0–4000 Ω | ±0.35 Ω | ±0.015 Ω |
| Pt100 | −200 a 850 °C | ±0.10 °C | ±0.003 °C |
| Pt1000 | −200 a 850 °C | ±0.10 °C | ±0.005 °C |
| Cu50 | −50 a 150 °C | ±0.10 °C | ±0.005 °C |
| Cu100 | −50 a 150 °C | ±0.10 °C | ±0.003 °C |
Thermocouple accuracy:
| Signal | Recommended range | Precisión (25 °C) | Temperature drift (/°C) |
|---|---|---|---|
| Millivolt | −100 to +100 mV | ±0.025 mV | ±0.001 mV |
| B | 500 a 1810 °C | ±0.77 °C | ±0.050 °C |
| E | −200 a 1000 °C | ±0.20 °C | ±0.025 °C |
| J | −190 a 1200 °C | ±0.35 °C | ±0.01 °C |
| K | −200 a 1372 °C | ±0.40 °C | ±0.025 °C |
| N | −190 to 1300 °C | ±0.50 °C | ±0.015 °C |
| R | 0 to 1768 °C | ±0.75 °C | ±0.023 °C |
| S | 0 to 1768 °C | ±0.70 °C | ±0.023 °C |
| T | -200 a 400 °C | ±0.35 °C | ±0.015 °C |
Two things an engineer should read off these tables. First, the RTD accuracy figures are specified for the 4-wire connection. The manual states that 2-wire and 3-wire connections meet the same figures only after the lead-wire resistance error is excluded. In a real 2-wire or 3-wire installation, lead resistance adds error that these numbers do not include. If you wire 2-wire to save conductors, budget for that.
Second, the temperature drift column matters because the headline accuracy holds at 25 °C. A cabinet that runs at 50 °C carries an additional drift of roughly 25 times the per-degree figure. For a Pt100 at ±0.003 °C/°C, that is small. Run the same arithmetic for your worst-case cabinet temperature before you trust the 25 °C number in a hot enclosure.
Common-mode and differential-mode rejection are both specified at ≥70 dB at 50/60 Hz, which is what lets the device hold these figures in an electrically noisy cabinet.
Power, isolation, and environmental limits
| Parámetro | Valor |
|---|---|
| Salida | 2-wire, 4–20 mA / HART, linear to input |
| Fuente de alimentación | 11–35 VDC |
| Canales | Two |
| Cableado RTD | 2-, 3-, 4-wire |
| Temperatura de funcionamiento | −40 a 85 °C |
| Humedad | 0–95% RH |
| Tiempo de inicio | ≤5 s |
| Hora de actualización | 0.8–1.3 s (depends on sensor type and wiring) |
| Enclosure rating | IP20 (terminals IP00) |
| Isolation voltage | 1000 VAC |
| Power supply influence | ±0,0051 TP3T/V |
| EMC | GB/T 18268.1-2010 |
A few of these drive design decisions. The 11–35 VDC input is wide enough to run on most 24 VDC cabinet supplies with margin. The 1000 VAC isolation separates the sensor side from the loop, which protects the control system from field-side faults and breaks ground loops. The IP20 enclosure (IP00 at the terminals) confirms this is a cabinet device, not a field-mount one; it needs an enclosure for any environment dirtier than a clean control room.
The update time of 0.8–1.3 s depends on sensor type and wiring. For slow thermal processes that is fine. If you are closing a fast control loop on temperature, confirm that update rate suits your loop.
Failure-mode signaling (NAMUR-style behavior)
The transmitter drives its output outside the normal 4–20 mA band to signal faults, which is how a control system distinguishes a real reading from a broken one.
| Condition | Output current |
|---|---|
| Normal linear output | 3.8 ≤ I ≤ 20.8 mA |
| High failure (limit) | 21.75 ≤ I ≤ 23 mA |
| Low failure (lower limit) | 3.5 ≤ I ≤ 3.75 mA |
These thresholds let you configure the DCS to alarm on sensor break or out-of-range conditions instead of reading a frozen value as valid. The behavior is consistent with NAMUR NE 43-style downscale/upscale fault signaling. Confirm the exact drive direction (upscale vs. downscale on break) in your configuration to match your alarm philosophy.
Selection logic: when this device fits
Reading the specifications back as a selection checklist:
Choose a dual-channel rail-mount transmitter like this when you have two measurement points close together and want one module instead of two, or when you need Pt100-based cold-junction compensation at ±0.15 °C rather than the ±0.5 °C internal figure. Confirm your sensor combination against the manual’s input matrix first.
Wire 4-wire RTD when accuracy is the priority, because the published accuracy figures assume it and 2-/3-wire installations carry uncompensated lead resistance.
Check the operating temperature of the actual cabinet against the drift figures, not just the 25 °C headline accuracy.
Confirm the device’s protection rating suits the enclosure: IP20 means it relies on the cabinet for ingress protection.
This is a HART device, so it also supports digital configuration and diagnostics over the 4–20 mA loop, which matters if your asset-management system reads instrument status.
Specifications and configuration details
Full input combination matrix, wiring diagrams, and HART configuration are in the NCS-TT106H-R data book. For the data book or to discuss whether the dual-channel rail-mount form fits your I/O plan, the datasheet and contact details are on the product page: https://www.microcybers.com/en/rail-mounted-2-ch-hart-temperature-transmitter/
