The Model 6.4 features an Integral Sensor and function is to calculate Vitamin D3 IU per Minute International Units (IU) of natural vitamin D3 (converted from 7-DHC) per minute of ultraviolet B exposure.
Specifications Radiometer
Model 6.4
Irradiance Range 280-298 nm
Response Total UVR - 280-400nm, Diffey EAS
Resolution 1 IU/Minute
Conversion Rate 3.0 Readings/Sec
Display 3.5 Digit LCD
Operating Temps 0° C to 40° C
Operating Humidity 5% to 80% RH
Accuracy ±10% REF.NIST
Dimensions (LxWxD) 10.5 x 6 x 2.2 cm
Weight 110 Grams
Power Source 9-Volt DC Battery
Sensor Aluminum Galium Nitride (AIGaN)
Diffuser Metal Oxide IF/Teflon Diffuser


There is a constantly increasing amount of evidence from research worldwide that suggest maintaining adequate Vitamin D levels is responsible for the prevention of many modern diseases.

Technically not a "vitamin," vitamin D is in a class by itself. Its metabolic product, calcitriol, is actually a secosteroid hormone that is the key that unlocks binding sites on the human genome. The human genome contains more than 2,700 binding sites for calcitriol, those binding sites are near genes involved in virtually every known major disease of humans.

Current research has implicated vitamin D deficiency as a major factor in the pathology of at least 17 varieties of cancer as well as heart disease, stroke, hypertension, autoimmune diseases, diabetes, depression, chronic pain, osteoarthritis, osteoporosis, muscle weakness, muscle wasting, birth defects, periodontal disease, and more.

Vitamin D's influence on key biological functions vital to one's health and well-being mandates that vitamin D no longer be ignored by the health care industry nor by individuals striving to achieve and maintain a greater state of health.


To enquire on the the Model 6.4 please click on the link below or use the contact page.

When requesting a quote please provide quantity and suburb/state for postage/delivery details.


Aluminum Galium Nitride (AIGaN) Photodiode with UG-11 filter and teflon diffuser cap.

Outdoors, take the meter reading pointing straight up for global normal (direct plus diffuse) irradiance. Indoors, take the meter reading at "body position" distance from the UVR lamp array. You will note outdoors that clear-sky solar zenith angle (SZA) has the largest effect on meter reading being highest during summer noon times. Sky clarity (deep blue) and altitude will also influence readings higher. Indoors, the percent UVB and wattage of UVR lamps have the largest effect on readings. They are typically 3-5 times higher than solar noon values.

The fundamental basis of this meter's calibration seeks to equate 1 minimal erythemal dose (MED) with 1000 IU of Vitamin D3 for skin type 2 at 10% body exposure (face and lower arms) with no base tan or SPF at age 20 average young adult. Interactive excel spreadsheet "utility" software will be provided with each meter to adjust the above parameters and dose duration based on your personal metrics. See screen shot of this utility below:


The formula constants embedded in the utility conversions of meter readings with IU and Eeff dose rates are:

> 1000 IU = 1 Med.
> 1 IU/min = 1/1000 Med/min (or .06 Med/hr, which = 1/16.666 Med/hr).
> 1 Med/hr = 2.333333 UVI and 1 Med/hr = 16.66666 IU/min.

Thus the conversion constant for IU/min to UVI is 16.66666666 / 2.3333333 = 7.14285714285.
Formulas for other parameters (skin type, tan level, age, etc are footnoted and available on request).

How to use the meter:
For the casual user seeking about 1000 IU from face/arms exposure, there is no need to use the spreadsheet parameters. Simply point the meter at UV source and divide the reading into 1000 for minutes of exposure. Done. Cautionary note: if you are white type 2 skin (usually burns, sometimes tans) start out at 50-75% of calculated minutes until your tolerance to UVR increases after about 4 exposures. If you are higher skin type and/or have a base tan, you will synthesize less than 1000 IU.

For the user seeking more accurate dose levels, please use the Utility and determine appropriate dose level for your particular metrics. Here is a "by the numbers" procedure:

1. Set meter reading in parameter 1.
2. Set hypothetical dose to same minutes as shown in parameter 1 sidebar.
3. Set parameter 2 skin type (note IU decrease as skin type increases)
4. Set % body (note IU increase as % body exposure increases above 10%)
5. Set SPF if any (note IU large decrease as SPF increases above 0)
6. Set % tan (note IU decrease as tan level increases)
7. Set age (note IU decrease above and below baseline 20yr old)
8. Return to parameter 2 and adjust dose duration up or down to see approximate IU for exposure session

Take care to keep dose below 1 MED for type 2 with 0% tan. Note that dose duration cannot be set above 4 MEDs for fully tanned sunburn avoidance purposes. Also note that after 2 MEDs the amount of IU will stop increasing as the body is much less able to synthesize cumulative Vit D3 above ~1.5 MEDs.

Battery operation voltage is 9V down to 6.5V. Below 6.5V the LCD numbers will begin to dim, indicating the need for battery replacement. Under "typical" service load, the battery should last about 2 years.

Fitzpatrick skin types: please see for descriptions.

Note: Skin type 1 people or anyone taking medications that increase UV sensitivity should avoid deliberate UV exposure except on the advice of their physician. People with sun sensitive disorders like Xeroderma Pigmentosum (XP) must of course avoid any UV exposure, and utilize diet plus supplements to maintain vitamin D levels as recommended by their doctor.

Generally, for most people, UV exposure in moderation can be beneficial; but UV overexposure can be harmful. Studies have shown that long term UV exposure may also increase the risk of photoaging and some kinds of skin cancer. As with almost everything else in daily life, a proper balance between UV benefit and risk is important. Consult your personal physician for an opinion regarding your particular skin type and family history before utilizing UVB as a primary source for vitamin D.

For more information on Vitamin D and sunshine visit the Vitamin D Council