6.5: Level and Span Controls
- Page ID
- 57862
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The level control sets the midpoint temperature displayed on the screen. Adjusting the level shifts the entire temperature scale up or down.
Span
The span control determines the width of the temperature range displayed. A smaller span increases contrast, while a larger span reduces contrast.
Practical Use of Level and Span
For Level I inspections:
- Reduce span to enhance contrast
- Adjust level to center the temperature range on the area of interest
- Avoid over-adjustment that exaggerates noise
Level and span adjustments affect image appearance only, not actual temperature data.
High-Range vs. Low-Range Thermal Cameras
Thermal cameras are commonly configured with either low-temperature ranges or high-temperature ranges, and the selected range directly affects thermal sensitivity, image contrast, and appropriate inspection applications.
Low-Range Thermal Cameras
Description
- Optimized for temperatures near ambient conditions
- Designed to detect small temperature differences with high sensitivity
Positives
- Higher thermal sensitivity (better ability to resolve small ΔT)
- Improved image contrast for low-temperature inspections
- Better suited for subtle thermal patterns
Negatives
- Limited maximum temperature capability
- Hot targets may saturate or lose detail
- Not suitable for very high-temperature applications
Common Use Cases
- Building envelope inspections
- Roof moisture surveys
- Mechanical equipment inspections
- Solar photovoltaic (PV) inspections
- Energy audits
High-Range Thermal Cameras
Description
- Designed to measure elevated and extreme temperatures
- Commonly used in industrial and electrical environments
Positives
- Capable of measuring very high temperatures
- Reduced risk of saturation on hot components
- Suitable for energized electrical and process equipment
Negatives
- Lower sensitivity at near-ambient temperatures
- Reduced contrast for subtle temperature differences
- Less effective for low-temperature building applications
Common Use Cases
- Electrical inspections of energized equipment
- Furnaces and kilns
- Refractory and process monitoring
- High-temperature industrial assets
Level I Selection Reminder
Selecting the appropriate temperature range is essential.
Using a range that is too high or too low for the application can reduce image quality and may lead to misleading thermograms, even when the camera is operating correctly.
|
Feature |
Low-Range Thermal Camera |
High-Range Thermal Camera |
|
Primary Design Purpose |
Detect small temperature differences near ambient |
Measure elevated and extreme temperatures |
|
Typical Temperature Range |
Near ambient to moderate temperatures |
Moderate to very high temperatures |
|
Thermal Sensitivity |
Higher sensitivity (better for small ΔT) |
Lower sensitivity at ambient temperatures |
|
Image Contrast (Low ΔT) |
Excellent |
Reduced |
|
Risk of Saturation |
Higher when viewing hot targets |
Low |
|
Best For |
Subtle thermal patterns |
Hot components and energized equipment |
|
Common Applications |
Building envelopes, roofs, mechanical systems, solar PV |
Electrical inspections, furnaces, refractory systems |
|
Limitations |
Cannot accurately measure very hot objects |
Poor resolution of small temperature differences |
|
Typical Inspection Environment |
Ambient or slightly elevated temperatures |
High-energy or industrial environments |