How are light energies measured?

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Category: Lighting
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Posted by Conservation Answers(Questions:33:Answers28)
Answered On 25 February, 2014 12:19 am

It is good practice to measure and monitor the amount of light falling on objects in your collection storage and display areas. Light and UV measuring equipment is available that will allow you to do this. We recognise, however, that the cost of this equipment may be prohibitive, and it may not even be a wise allocation of funds for a piece of equipment that may not be used very frequently. If your museum, gallery or library is not able to purchase this equipment, you may be able to borrow them from a larger institution in your area, or perhaps pool with several collections in your region.

The following sections provide information about measuring light levels, assuming the appropriate equipment is available. Even if you do not have the equipment, continue working through these sections as they will help you to better understand the recommended light levels for museums and heritage collections.

Measuring Visible Light

Visible light is measured in units called lux and can be measured with a device called a lux meter. The meter has a sensor that is placed close to the object, or area being measured that is directed towards the light source. It gives a direct reading, either by a needle on a scale or in a digital readout, of the amount of light falling on the sensor.

lux meter
A lux meter

When setting up your exhibitions or reviewing your current building, it is handy to have a lux meter. By measuring light levels in various locations within your collection area, you can get an idea of which areas are suitable for certain object types. You can also get an idea of what parts of your building require improved lighting and what areas need to have light levels reduced.

Measuring light levels with a lux meter
Measuring light levels with a lux meter

Measuring UV Radiation

The amount of UV radiation is measured in microwatts of energy per lumen of light, (microwatts/lumen or in short hand µW/lm). This is an indication of the proportion of total light that is in the UV range, or high energy range. It is measured with an UV meter. The meter has two sensors which, when placed near to the object or location being measured and pointed towards the light source, will give a reading of the amount of UV energy. This is expressed as a proportion of the total light falling on the sensors. The reading is either by a needle on a scale or a digital read out.

A UV meter
A UV meter

Measuring IR Radiation

IR radiation, being heat energy, causes objects to heat up. It can therefore be measured directly with a thermometer. Temperature readings should be taken in proximity to the items on display. In particular, they should also be taken near windows and inside closed showcases where internal lights can cause temperatures to rise steeply.

Measuring temperature near displayed item
Measuring temperature near displayed item
1
Posted by Conservation Answers(Questions:33:Answers28)
Answered On 11 December, 2013 4:33 am

It is good practice to measure and monitor the amount of light falling on objects in your collection storage and display areas. Light and UV measuring equipment is available that will allow you to do this. We recognise, however, that the cost of this equipment may be prohibitive, and it may not even be a wise allocation of funds for a piece of equipment that may not be used very frequently. If your museum, gallery or library is not able to purchase this equipment, you may be able to borrow them from a larger institution in your area, or perhaps pool with several collections in your region.

The following sections provide information about measuring light levels, assuming the appropriate equipment is available. Even if you do not have the equipment, continue working through these sections as they will help you to better understand the recommended light levels for museums and heritage collections.

Measuring Visible Light

Visible light is measured in units called lux and can be measured with a device called a lux meter. The meter has a sensor that is placed close to the object, or area being measured that is directed towards the light source. It gives a direct reading, either by a needle on a scale or in a digital readout, of the amount of light falling on the sensor.

lux meter

A lux meter

When setting up your exhibitions or reviewing your current building, it is handy to have a lux meter. By measuring light levels in various locations within your collection area, you can get an idea of which areas are suitable for certain object types. You can also get an idea of what parts of your building require improved lighting and what areas need to have light levels reduced.

Measuring light levels with a lux meter

Measuring light levels with a lux meter

Measuring UV Radiation

The amount of UV radiation is measured in microwatts of energy per lumen of light, (microwatts/lumen or in short hand µW/lm). This is an indication of the proportion of total light that is in the UV range, or high energy range. It is measured with an UV meter. The meter has two sensors which, when placed near to the object or location being measured and pointed towards the light source, will give a reading of the amount of UV energy. This is expressed as a proportion of the total light falling on the sensors. The reading is either by a needle on a scale or a digital read out.

A UV meter

A UV meter

Measuring IR Radiation

IR radiation, being heat energy, causes objects to heat up. It can therefore be measured directly with a thermometer. Temperature readings should be taken in proximity to the items on display. In particular, they should also be taken near windows and inside closed showcases where internal lights can cause temperatures to rise steeply.

Measuring temperature near displayed item

Measuring temperature near displayed item

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