In many industrial applications, thermocouples are used to measure temperatures in furnaces, pipelines, tanks, and other remote areas.
Traditionally, thermocouples are connected directly to controllers via expensive compensation cables. These are special alloy cables that are matched to the material of the thermocouple (e.g. NiCr/Ni for type K).
The longer the cable run, the higher the cost. For distances over 50–100 metres, cable costs can account for a significant proportion of the project budget.
What is NPT3?
The NPT3 is a signal conditioning transmitter that is built directly into the head of a DIN-standard thermocouple sensor. It:
- Receives the millivolt signal from the thermocouple
- Converts it into a standardized 4–20 mA current signal
- Transmits the signal to the controller using a regular shielded cable
What are the benefits?
- No need for compensation cables (types K, J, S, etc.), which typically cost €3–€6 per meter.
- Standard shielded copper signal cables (e.g., LiYCY 2×0.5 mm²) starting at €0.8 per meter can be used instead.
- NPT3 eliminates the negative effects of cable length and ambient temperature on measurement accuracy.
- Signal cable lengths of up to 500 meters or more can be used—without any loss of signal quality.
Example: Cost Comparison
Scenario 1
Scenario 2
Let us imagine that we need to connect a thermocouple at a distance of 100 meters to the controller:
|
Option |
Cable type |
Price per m |
Total cost |
|
Without NPT3 |
Compensation cable NiCr/Ni |
€5.00 |
€580 |
|
With NPT3 |
Shielded copper cable |
€1.00 |
€230 |
Savings: €350. The farther the thermocouple is from the controller, the greater the savings.
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| Total cost of equipment with NPT3 | |
|---|---|
| Total cost of equipment without NPT3 | |
| Total savings with NPT3 |
Additional Savings: On Controllers Too
Using the NPT3 not only reduces cable costs, but also controller expenses.
Controllers that connect directly to thermistors (e.g., Pt100) are typically more expensive due to specialized input circuitry and wire resistance compensation.
By contrast, controllers that accept 4–20 mA signals are widely available, standardized, and generally much more affordable.
With NPT3, you can opt for a simpler, cheaper controller without compromising performance.
Note: akYtec controllers are universal and support thermocouples, RTDs, voltage (0–10 V), and current (4–20 mA) signals.
NPT3: Not Just About Cost
You also get:
- Strong resistance to electrical interference (via 4–20 mA signal)
- Improved measurement accuracy
- Simplified wiring and maintenance
- Compatibility with any controller
