Temperature measurement is a key foundation of many industrial processes. It affects product quality, safety, energy efficiency, and process control. However, even high-precision sensors can deliver inaccurate values if mounted incorrectly or placed in unfavorable positions. Proper placement of temperature sensors is therefore often underestimated – yet it is crucial for reliable measurement results.
In this article, we will show:
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Why proper sensor placement is so important,
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What typical installation mistakes occur,
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How to avoid them,
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And what role environment, installation situation, and medium play.
Why Proper Placement Is So Crucial
A temperature sensor does not measure the temperature of the entire system but only at its immediate contact point. For this value to be representative, the sensor must be located where it is truly relevant for process control or quality assurance.
Examples:
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In a pipeline, the medium temperature should be monitored – a sensor placed in the flow core is better than one near the pipe wall.
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In an oven, the product temperature matters – not the air temperature in the corner.
Consequences of incorrect placement:
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Inaccurate or delayed readings
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Oscillating or unstable control loops
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Quality issues due to over- or undertemperature
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Energy losses due to excessive safety margins
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Safety risks in thermally sensitive processes
Common Mistakes in Temperature Sensor Placement
In practice, typical mistakes often occur that can be easily avoided – if they are known. The following table provides a quick overview:
Table: Common mistakes in temperature sensor placement and useful tips
| Error | Description | Consequence | Tip to Avoid |
|---|---|---|---|
| Sensor too close to wall or pipe wall | Temperature near the wall is slower to change and often cooler/warmer than in the flow core | Incorrect readings during rapid changes | Place sensor in the flow core or well-mixed area |
| No direct contact with the medium | Sensor is in a thermowell but not properly immersed, or medium flows past it | Delayed or distorted measurement | Ensure full immersion and proper medium flow around the well |
| Sensor in dead zone or air pocket | Measures stagnant air or isolated spots (e.g., between insulation and pipe) | Very sluggish response or inaccurate average | Place in well-circulated or actively heated zones |
| Heat conduction via connection point | Heat is conducted away through wiring | Reading is falsely reduced | Use thermal insulation behind the measuring point |
| No thermal decoupling | Sensor too close to housing, clamps or walls | Ambient temperature affects sensor | Provide thermal separation or physical spacing |
| Incorrect immersion depth in thermowells | Sensor does not reach far enough into the thermowell | Slow response, unstable readings | Use at least 2/3 of well length, insert as deep as possible |
| Mounted against flow direction | Sensor "faces the wind" or is not directly surrounded by flow | Temperature not properly transferred | Install in flow direction or calm flow area |
| Incorrect polarity during connection | Especially critical with thermocouples | Value jumps or remains constantly wrong | Always connect using correct color code or standard |
Tips for Typical Applications
Pipelines (Liquids or Gases)
Recommendation:
- Use sensors with thermowells
- Immersion depth should be 5–10× the diameter
- Mount at a 90° angle to flow direction if possible
- Avoid installation directly behind pumps, bends, or valves (turbulence)
Watch out for:
- Ensure proper medium circulation around the thermowell
- Don't forget insulation over the thermowell
Tanks and Vessels
Recommendation:
- Place sensor at medium level (not too low or high)
- Use multiple measuring points for large tanks
- Prefer moving medium (e.g., through circulation)
Watch out for:
- Do not mount directly against walls (temperature distortion)
- Use thermal decoupling for sensitive products
Air Ducts and HVAC Systems
Recommendation:
- Place sensor in center of duct
- Observe flow direction
- Use protective cage in high-velocity air
Watch out for:
- Avoid dead zones or wall proximity
- Plan for a mixing distance before the measurement point
Oven, Dryer, Process Chamber
Recommendation:
- Place sensor as close as possible to the product
- If not possible: combine product and chamber temperature measurement
Watch out for:
- No direct radiation or airflow on the sensor
- Use thermal shielding at high heat
Selecting the Right Sensor Type
Not every sensor is suitable for every installation scenario. Here’s a brief overview of common types and their typical applications:
| Sensor Type | Typical Application | Special Features |
|---|---|---|
| PT100/PT1000 | Industrial standard measurements for liquids, gases, solids | High accuracy, often used with thermowells |
| Thermocouple (e.g., Type K, J, T) | Fast processes, high temperatures, welding | High dynamics, polarity must be correct |
| Mineral-insulated thermocouple | Confined spaces, tight bends | Flexible and bendable |
| Surface sensor | Housings, pipes, components | Only for approximate values, poor on insulated surfaces |
| Cable sensor | Room air, control cabinets | Easy to install, low thermal inertia |
Installation – Pay Attention to Details
- Clean contact surfaces: A sensor only measures accurately if it has proper contact or flow.
- Use thermal paste (if applicable): Improves thermal coupling.
- Secure mounting: Loose sensors cause fluctuating readings – vibration-proof installation is essential.
- Protect against moisture and chemicals: Especially in process environments, check the IP protection rating.
- Regular visual inspections: Sensors can shift, bend, or become obstructed – especially in mobile systems.
Don't Forget Calibration
Even with perfect placement, only calibrated sensors provide reliable values. ICS Schneider Messtechnik offers DAkkS and factory calibrations – tailored to your requirements. Depending on the industry or standards (e.g., ISO 9001, IFS, GMP), different intervals are necessary. Feel free to contact us!