Mercury Vapour Lamps:
ExoTerra Solar Glo 125watt Lamp
 
broadband meter readings and thermal gradient  
iso-irradiance charts
spectrum - UV + Visible light
spectral analysis - photobiologically active UV

 

 

 

 
 

Lamp Description

ExoTerra Solar Glo 125watt Lamp
125watt, R38 self-ballasted mercury vapour lamp
Rolf C Hagen (UK) Ltd., Castleford, West Yorkshire WF10 5QH

                                                                                                          Lamp refs: BEMV12, BEMV13 (2012-2013)

Broadband Meter Readings

 
UV Index (Solarmeter 6.5) Total UVB (Solarmeter 6.2) and Illuminance (Lux meter readings)
New lamp (105hrs use)                                Distance from lamp surface (cm)
15
20
25
30
35
40
45
50
55
60
UV Index (BEMV12)
9.8
7.2
5.3
4.2
3.2
2.6
2.1
1.8
1.5
1.3
UV Index (BEMV13)
7.6
5.3
3.8
2.9
2.2
1.8
1.5
1.2
1.0
0.8
Total UVB (µW/cm²) (BEMV12)
189
134
99
74
58
47
39
32
26
23
Total UVB (µW/cm²) (BEMV13)
162
111
80
59
46
37
29
24
20
17
lux   (BEMV12)
48,200
31,900
22,800
16,900
13,200
9,630
7,840
6,250
5,160
4,330
lux   (BEMV13)        
49,900
31,300
22,200 15,800 11,700
9,330
7,590
6,200
5,240
4,310

 

Longevity
Decay (reduction in UVI with use) (BEMV12) (BEMV13)
105 h (10 days normal use) 44% 60%
no other data available
   
Electrical consumption            (BEMV12) (BEMV13)
130 watts 127 watts
Colorimetry (from spectral data)
  (BEMV12) (BEMV13)
CCT (human eye) 3,462K 3,709K
CRI (Ra) (human eye) 17.7 18.6

Visible beam  (lamp to surface distance = 30cm)
The concentric rings drawn on the card are 5cm apart. This lamp produces a moderately diffused beam with a stronger circle of light about 5cm across, focused slightly off-centre from the axis of the lamp.

Thermal Gradient  (lamp to surface distance = 30cm)
Surface temperature (°C) measured with infrared non-contact thermometer, on open bench.
Distance from lamp to bench = 30cm. Time to equilibrate = 2 hours

(BEMV12)

Distance from central point directly beneath lamp
0 cm 5 cm 10 cm 15 cm 20 cm 3 m (room temperature)
White wooden block 31.3 30.5 28.6 27.2 25.8 19.4
Unpainted wooden block
34.1 32.4 30.2 28.5 26.8 19.4
Black wooden block
37.1 35.0 32.1 30.4 28.7 19.4

At a reasonable basking distance in a well-ventilated vivarium, this lamp may not always be able to create a sufficiently high surface temperature across a wide enough area to create a basking zone for larger sun-loving species. Additional lamps (such as incandescent lamps on a dimming thermostat) may be used to control basking temperatures.

Iso-Irradiance Chart       
The small tortoise (carapace length 15cm) is drawn to the same scale as the charts and is placed so that its eye level is 30cm beneath the lamp. This is solely to enable comparison between charts, NOT to indicate suitable lamp distances, which will vary according to individual species requirements.
NB: To help prevent glare and other eye problems from the visible light, and thermal burns from infrared radiation, even if UV output appears safe at close range, we also recommend a minimum distance of at least 30cm, and/or maximum irradiance around 100,000 lux (equivalent to very intense sunlight) from ALL mercury vapour and metal halide lamps.

This lamp has a narrow beam. The output after burning-in is also low owing to extremely rapid decay over the first few days of use. After 105 hours - the equivalent of about 10 days of use in a vivarium - the lamp is creating a zone, at 30cm distance, that is only approximately 5cm in diameter with a UV gradient between UVI 2.0 at its edges and UVI 2.9 at its centre.

Spectrum - UV plus Visible Light

A mid-day solar spectrum with the sun close to the zenith (Solar altitude 85.4°, location San Bartolomé, Gran Canaria, June 21st 2011 Local time 14:00h) is overlaid for comparison (but note the different irradiance scales).



Spectrum - UV in more detail

This spectrum has:

  • typical features of a mercury vapour lamp: extremely discontinuous spectrum ("spikes") very unlike sunlight.
  • no detectable UVC or non-terrestrial UVB (wavelengths below 290nm).
  • solar-wavelength (295 - 320nm) UVB output, restricted to small "spikes" at 295, 302 and 313nm. These wavelengths are involved in vitamin D3 synthesis.
  • very low short-wavelength UVA output (320 - 350nm). These wavelengths are involved in the control of vitamin D3 synthesis.
  • high long-wavelength UVA output, but restricted to one "spike" at 365nm - reptile vision includes long-wavelength UVA.
  • Visible light spectrum (wavelengths 400 - 750nm) mainly restricted to only four colours from the mercury arc, resulting in poor colour rendering (to the human eye).

Spectral Analysis - photobiologically active UV (wavelengths from 270 - 350nm)

  • There is UVB in the wavelengths which enable vitamin D3 synthesis in skin.
  • This lamp emits no hazardous UVC or non-terrestrial UVB (below 290nm).
  • The proportion of UVA from 320 - 335nm, important for natural prevention of excessive vitamin D3 synthesis, is low. This is typical of mercury vapour lamps. It is still unknown as to whether this has any long-term health consequences.

 

      

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