I believe the original intent of this requirement was to protect the totally
technically clueless from harm. The test finger is used simply since it is
available to anyone doing safety evaluations. Introduction of a new tool is
really a major burden.
I have typed out the key phrases in 950 following. As always the information
in 950 is scattered and you have to look for it.
The major message is that trained personnel are permitted access to parts of
product that might be dangerous, and 'operators' are denied access. Sorry for
the length of the following......
Bob Den Bleyker
ref IEC-950 second edition, with 3d amendments
1. 1.2.14.5 Service Personnel: Persons having appropriate technical
training and experience to be aware of hazards to which they are
exposed in performing a task and of measures to minimize the danger to
themselves or any other persons.
2. 1.2.14.5 Operator: Any person other than service personnel.
3. 1.2.8.7 Hazardous Energy Level: A stored energy level of 20 J
or more, or an available continuous power level of 240 VA or more, at
a potential of 2 V or more.
4. 1.2.7.1 Operator Access Area: An area to which, under normal
operating conditions, one of the following applies:
access can be gained without use of a tool, or
the means of access is deliberately provided to the operator, or
the operator is instructed to enter regardless of whether or not
tools are needed to gain access.
5. 1.2.7.2 Service access area: an area. other than operator access
area, where it is necessary for service personnel to have access even
with the equipment switched ON.
6. 1.2.7.3 Restricted Access Location: A room or space where equipment
is located, and where either:
access can be gained by service personnel with the use of a special
tool or lock and key, or access is controlled.
7. 1.2.7.4 Tool: A screwdriver or any other object which can be used
to operate a screw, latch, or similar fixing means.
8. 2.1.5 There shall be no energy hazard in an operator access area.
Compliance is checked by means of the test finger, figure 19, page 239.
In a straight position, applied without appreciable force. It shall not
be possible to bridge with this test finger two bare parts, one of which
may be an earthed conductive part, between which a hazardous energy
exists.
The test finger is shaped much like a human finger, 12mm dia. with a
tapered and rounded end. Overall length is 180mm. There is a disk
of 75mm placed to limit penetration to 180mm into smaller openings.
