Temperature Transmitters: Head Mounted, DIN Rail, and Rack Mounted Options

Temperature transmitters play a vital role in delivering accurate and reliable readings from the field to the control room. While many industrial temperature measurements still rely on direct millivolt signals from thermocouples or RTDs, local signal conditioning via transmitters is increasingly common—especially as distances grow or noise immunity becomes critical.

Contents

1. Why Use a Temperature Transmitter?
2. Transmitter Types and Installation Options
3. Choosing the Right Approach

Why Use a Temperature Transmitter?

Transmitting millivolt-level sensor signals over long distances can introduce noise and require expensive cabling. A 4–20 mA current loop, on the other hand:

• Uses lower-cost twisted pair wiring
• Provides robust, noise-immune signal transmission
• Offers better signal strength and longer range

Installing a local transmitter often becomes the smarter and more economical choice once signal distance increases beyond a certain point.

Transmitter Types and Installation Options

1. Head-Mounted Transmitters
• Installed directly at the sensor head (“hockey puck” style)
• Convert low-level signals at source to 4–20 mA
• Offer the most accurate representation of the actual sensor reading
• Reduce costs by eliminating extension or screened cables
• Ideal for short to medium distances and electrically noisy environments
Limitations:

• Exposed to harsh environmental conditions
• Limited cold junction compensation accuracy
• Electronics can drift with temperature variations
2. DIN Rail or Rack-Mounted Transmitters
• Installed remotely in control cabinets or racks
• Accept multiple sensor inputs for centralized conditioning
• Easier access for configuration and maintenance
• Suitable for environments where direct sensor mounting is impractical
Trade-offs

• Require higher-grade extension/screened cables from sensor to panel
• Greater risk of signal degradation before transmission

Choosing the Right Approach

There’s no one-size-fits-all solution. The decision depends on:

• Sensor-to-control room distance
• Environmental conditions
• Required signal integrity
• Installation and maintenance preferences
• Budget constraints

With falling transmitter costs and more advanced digital options, it’s now viable to use transmitters even for relatively short runs.

Further Reading

RTD vs Thermocouple – Choosing the Right Sensor
Explore the features and characteristics of thermocouples and RTDs

RTD Output Tables
View Resistance versus Temperature tables for all Pt100 sensors.

What are the RTD colour codes?
Explore RTD colour codes and wiring configurations.