i've popped along to great Oakley cricket club this morning and as a fan of the sport i can
confirm there's absolutely nothing like the thwack of leather on willow on a blistering
summer's day but this is England so even on the sunniest of days there's always the threat of rain
grey clouds and the failing of the light but it's not just cricketers who are affected by bad light
workplaces and other environments can also create problems when poorly lit and at times
it may be necessary to measure light levels in a space or on a work surface to make sure that it's
getting enough light for the jobs to be carried out there with this in mind Metrel have created
the A1172 which is a lux meter sensor attachment that simply connects to your Metrel multi-function
tester and takes light readings in units of lux it's really really easy to set up it just takes a
square battery in the back there and then it plugs into the top of the multi-function tester it sits
really comfortably in the palm of your hand and it also has this coiled flex on it which you can
stretch out and move around without having miles of lead to get tangled up or trip over then it's
simply a matter of heading into the single tests menu and press on the screen here where it says
other and here you'll find various miscellaneous tests but the one we're really interested in
is the one marked lux now to carry out a test you simply turn the lux meter on and then press
the test button on the screen here or the silver run button on the front and it will immediately
start testing and give you a readout in lux now in recent years we've kind of got used to testing
equipment that takes a reading and gives you a value most multi-function testers won't show a
continually changing value for resistance when testing for continuity or insulation unless you
change the settings to do so but you'll notice that it doesn't give you a fixed steady and final
value when you're doing this test what it's doing here is it's giving you a continually changing
and fluctuating value this is because light levels are surprisingly variable if we take a room with
a single point source of illumination then the light level will be brightest directly below it
then as we move away from the source the light level will drop further and further off you
can actually use this change in light level to calculate what's called the uniformity of lighting
in a space but more of that in a future video it's also sensitive to the angle that light hits it at
if light is falling directly onto a surface at 90 degrees then it will receive the maximum amount
available at that point but if the light hits the surface at an angle because the fitting or surface
is tilted then something called the cosine rule comes into effect and reduces the light level even
further another handy function of the lux meter is that you can set a lower limit to the light level
and the multi-function tester will alert you if the measured value drops below that point so for
example table 12.2 of the SLL lighting handbook states that the light level on a working surface
in an office should be an average of 300 lux so you could set your tester to 300 lux and measure
at various points on the surface if it drops below the value stated then the multi-function tester
will let you know bear in mind though that may not necessarily be a problem as it's the average
value that needs to be above 300 looks but it's a good starting point where it would also be really
useful is in measuring the light level along an escape route when emergency lighting is required
section 4.4 of the electrician's guide to emergency lighting states that for escape routes
up to two meters wide the horizontal illuminance is on the floor along the centreline of an escape
route shall not be less than one looks and the central band consisting of not less than half
of the width of the route shall be illuminated to a minimum of 50 percent of that value so you
could use the lux meter at floor level and check that the light level doesn't drop below one looks
when the emergency lighting is on and that it doesn't drop below 0.5 looks anywhere along that
central band the multi-function tester can be set to 0.5 looks and actually will go as low as 0.1
looks as the minimum value if required once you've found the lowest value along that centreline you
could also use the lux meter to make sure that the highest value along it isn't over 40 times the
lowest which is also a requirement for emergency lighting so there we go that's the A1172 luxmeter
it's a really simple to use and valuable addition to the range of accessories available from Metrel
and one that would be perfect for maintenance and initial verification of lighting levels or even
investigation into complaints about lighting levels in workplaces but as always we want to
hear from you do you ever calculate light levels on a job prior to installation
do you ever verify that the correct level of illumination has been achieved
after the lighting installation is complete do you think that understanding lighting is
something that electricians in general need to work on whatever your thoughts
and questions please leave them in the comments section below because if your lighting levels
aren't correct then quite frankly it's just not cricket thank you very much for watching