Both probes come out of IEC 61032, both get pushed against the same enclosure, and both end up on the same report. They still answer different questions. Probe B asks whether a finger can touch a hazard. Probe C asks whether a thin tool, like a screwdriver shaft, can reach one. Mixing the two up produces reports that read well and mean nothing.
The physical difference
Probe B is the jointed test finger with a 12 mm diameter tip and a stop face, built to mimic a finger from knuckle to fingertip. The jointed middle lets the tip bend and probe ventilation slots the way a real finger would. Probe C is a straight bar of 2.5 mm diameter with a stop, representing a narrow tool. Probe D, at 1.0 mm, covers thin conductive parts like a wire end.
Different questions, different results
A slot that stops Probe B can still admit Probe C, and both outcomes can be acceptable, depending on which standard the product follows. A standard written around finger safety, household appliances for example, judges against Probe B. Standards protecting against tool access call for Probe C or D. Passing with C does not imply passing with B, and the reverse is not true either; the probes are not interchangeable, and neither is the paperwork.
| Probe | Geometry | Question it answers |
|---|---|---|
| B | 12 mm jointed finger with stop face | Can a finger reach a hazard? |
| C | 2.5 mm straight bar with stop | Can a thin tool reach in? |
| D | 1.0 mm pin with stop | Can a wire end or thin conductor touch? |
Reporting both on one product
Some products legitimately need both results, finger safety on the enclosure and tool access through drainage slots. Record which probe touched which opening, at which force, and photograph the borderline cases. A report line reading "accessible openings verified with Probe B and Probe C" without specifics invites the question "which opening with which probe", usually from the customer after shipment.
Sales Team