Thermal Camera Selection for Electrical Switchgear Inspection

A procurement-focused guide to selecting a thermal camera for switchgear maintenance: target size, working distance, field of view, NETD, focus, temperature measurement, and report workflow.

Last updated: 2026-09-24

Quick answer

For switchgear inspection, do not begin with a camera brand or a headline temperature range. Begin with the smallest fault feature that must be seen, the normal working distance, cabinet access constraints, and whether the inspection decision is visual screening or temperature measurement. Resolution, lens field of view, NETD, focus, and reporting workflow only make sense after those conditions are defined.

1. Define the inspection decision

A thermal image can support different decisions. A maintenance route may only need repeatable comparison images that reveal an abnormal connection relative to comparable phases. A troubleshooting task may need a smaller target to be resolved at a known stand-off distance. A condition report may need temperature values with documented assumptions. Put the intended decision in the request because it changes the required evidence from the supplier.

Ask the operating team for:

The smallest component or connection that must be distinguished.
Typical and maximum camera-to-target distance.
Whether a door, safety screen, or infrared window remains between camera and target.
Load condition and whether comparable phases or similar assets are available.
Whether the output is a route report, a work order attachment, or a one-off diagnostic image.

2. Size resolution from target and distance

Detector resolution alone is not a selection rule. The relevant question is how many detector pixels cover the target at the actual distance and lens setting. A wide lens covers more of the cabinet but assigns fewer pixels to a small lug or terminal. A narrower lens can improve target coverage from a safe distance but may make it harder to frame the whole asset.

Request the supplier to show, for the proposed lens, the field of view at the normal inspection distance and the predicted target coverage for the smallest feature. Keep the calculation in the RFQ response rather than accepting a generic statement such as high resolution.

3. Treat NETD as a detection aid, not an accuracy guarantee

NETD describes the camera's ability to distinguish small apparent thermal differences in an image. It can matter when the inspection objective is to identify weak contrast before a fault becomes obvious. It does not remove uncertainty from reflective metal, variable emissivity, changing load, poor focus, or a viewing angle that captures reflected radiation. Use NETD together with the actual lens, target coverage, and expected operating conditions.

4. Do not ignore focus and working geometry

Manual focus, autofocus behavior, minimum focus distance, and lens options are procurement requirements. A technically capable detector can still deliver weak evidence if the operator cannot reliably focus on a compact live cabinet from the available position. Ask for a demonstration or sample image under similar distance and target geometry.

5. Temperature readings need declared assumptions

For temperature measurement, record emissivity, reflected apparent temperature, object distance, atmospheric conditions where relevant, and any window compensation. FLIR documentation notes that emissivity and reflected temperature are especially important settings; it also lists distance, atmospheric temperature, humidity, and external IR-window compensation among the measurement parameters. Shiny or low-emissivity targets deserve particular caution because reflected radiation can dominate the displayed result.

Do not turn a single temperature threshold into a purchase specification unless the plant has an approved method for load condition, comparison baseline, and corrective action. Often the more defensible maintenance output is a documented anomaly against comparable components under similar load.

6. Specify the report workflow before buying

A route inspection needs more than a camera. Confirm how images are named, how visible-light and thermal images are paired, how measurement parameters are retained, whether templates can include asset ID and action notes, and how reports move into the maintenance system. A camera that creates isolated image files may add manual administrative work to every inspection round.

RFQ checklist

Ask every supplier to answer the same points:

Detector resolution and lens field of view.
Target coverage at the stated working distances.
Minimum focus distance and focus method.
NETD test condition and stated value.
Measurement range, stated accuracy, and calibration evidence.
Support for emissivity, reflected temperature, distance, humidity, and IR-window compensation.
Image, route, reporting, storage, and export workflow.
Training, service interval, and warranty terms.

When to use the free Blueprint

Use the free Blueprint when the team knows the asset and concern but cannot yet translate it into lens, resolution, measurement, and reporting requirements. Request an engineer review when there is an existing quote, a protected viewing path, or an internal maintenance method that needs a technical second look.

Sources for technical review

FLIR measurement parameters: https://docs.flir.com/T810411/en-US/latest/s10.html
FLIR thermographic measurement techniques: https://support.flir.com/docdownload/assets/web/4jau/en-us/T505000.xml.html
FLIR note on thermal sensitivity: https://www.flir.com/en-au/discover/security/perimeter-protection/the-importance-of-thermal-sensitivity-for-detection-accuracy/