Home News & Analysis Podcasts Series 20 – Episode 16 – can you trust the datasheet?

Series 20 – Episode 16 – can you trust the datasheet?

23 October 2026

This entry is part 35 of 35 in the series Electronic Specifier Insights

A datasheet can make two reed relays look nearly identical. But as Paige Hookway’s conversation with Robert King, Technical Sales and Product Development Manager at Pickering Electronics, explored, matching headline specifications do not necessarily mean matching performance. The important questions are how those figures were established, under what conditions, and how the component will behave in the intended application.

“Testing particularly is important with reed relays because they can be used in applications where very small changes in performance can have quite a big impact on the overall system,” King said. Contact resistance, operating and release characteristics, isolation, and high-voltage switching can all influence how a relay performs. A component may be small, but the system-level effects of its behaviour can be significant.

A specification needs context

King said a published number should be backed by performance data – not chosen simply because it looks impressive. Manufacturers need to consider repeatability, variation between parts and, crucially, the test conditions behind the result.

Two manufacturers may list the same parameter, but that does not mean they characterised it in the same way. A figure might represent an absolute maximum rather than a recommended operating point. As King put it: “The published number doesn’t always tell you the whole story.” Engineers comparing parts should therefore look beyond the largest voltage, current or power rating, and ask what the specification means in practice.

That context matters because engineers need different levels of information. Some want to know whether a part will work in their application; others need detailed data to model, simulate, and qualify a design. King said Pickering aims to make more technical information available upfront, so customers can better understand how relays perform under particular loads and conditions.

Testing in real-world conditions

Comparative testing has shown that relays tested on the bench under the same conditions can perform differently. One factor that may not appear on an individual-component datasheet is magnetic interaction. In dense systems, many relays may operate close together. King described boards containing hundreds of relays, where interaction between components can affect reliable operation.

Pickering’s testing includes measuring how relays behave when stacked on a board, to assess performance in a system rather than in isolation. The company also says it tests every relay before it leaves the factory. Checks can include coil operation and resistance, contact resistance, operating parameters and times, and dynamic contact resistance. For high-voltage products, testing can also examine performance under specified switching loads. King said the aim is for datasheet specifications to be a baseline customers can rely on.

Even with this testing, a customer’s own system can introduce additional factors. Board capacitance or circuit inrush, for example, may affect relay life. Pickering offers samples and application-specific test reports so engineers can evaluate components in their own setups. As King explained: “The customer should have the ability to test these samples in their real-world application to decide if they’re suitable.”

Ask how the number was reached

King noted that engineers are increasingly asking for information beyond conventional switching and coil specifications. Thermal EMF – the voltage generated by heat across a switch – can matter when measuring very low voltages or currents, yet it has not typically appeared on datasheets. Relay life and performance under specific loads can also require application-specific testing.

AI may make it faster to find and compare datasheet information, King said, but it can only work with information that is made available. Individual testing remains important because results can depend on application conditions.

His advice to engineers is simple: “How did you arrive at this specification? Could you provide some data behind it?” He also encouraged them to share the details of their application, including voltage, current, switching mode, temperature range, relay spacing, and expected operations.

To hear more from Robert King, you can listen to Electronic Specifier’s interview on Spotify or Apple podcasts.