New Light Meter

[Roy]

Got my Extech Model 401021 (Fc) Light Meter Adapter yesterday. It is a color corrected sensor and an adapter that plugs into your DMM. When connected to the DMM, and the DMM is set to mV, the the DMM readout is in foot candles. The adapter is callibrated usinga "Standard tungsten light source of 2856 degree K." Correction factors for the following types of light are given:

Mercury Lamp x1.14
Fluorecent Lamp x1.08
Daylight x1.00
Sodium x1.22
Metal Halide x1.00

Here is the $64 queston....Anyone got any idea where a 1w LED fits in the above lint?

I measured my PM6 DB400 R2H at one foot to be 1040Fc! MrBulk measured a similar PM6 at 2030 Lux at one meter.

 

[Doug S]

[ QUOTE ]
Roy said:
Got my Extech Model 401021 (Fc) Light Meter Adapter yesterday. It is a color corrected sensor and an adapter that plugs into your DMM. When connected to the DMM, and the DMM is set to mV, the the DMM readout is in foot candles. The adapter is callibrated usinga "Standard tungsten light source of 2856 degree K." Correction factors for the following types of light are given:

Mercury Lamp x1.14
Fluorecent Lamp x1.08
Daylight x1.00
Sodium x1.22
Metal Halide x1.00

Here is the $64 queston....Anyone got any idea where a 1w LED fits in the above lint?

I measured my PM6 DB400 R2H at one foot to be 1040Fc! MrBulk measured a similar PM6 at 2030 Lux at one meter.

[/ QUOTE ]

Yes. For a *white* LED, the daylight or Metal Halide correction factor will fit. Conveniently this is 1.00.

 

[aso]

Roy

The 2030 Lux that Charlie measured was with a module that had a DB700 in it.
1040 FC(11190 Lux!!!!!) with a DB400 seems a teenie bit high.
After reading the specs on your adapter there is a conversion of .1mV/Fc on the 200-2000 Fc range not 1mV/Fc. That would make your reading 104 Fc(1119 Lux), which makes more sense.

 

[PaulW]

Lux and footcandle numbers are the same for a given light when taken at the proper distance. For example,

A light that measures 1040 fc at one foot will read 1040 lux at one meter.

But at one foot on the lux scale (improper distance), it will read 11190.

And at one meter on the fc scale (improper distance), it will read 96.7.

Paul

 

[Roy]

Aso...the adapter is designed to be used on the 200mV scale of a DMM. My DMM is an auto rangeing meter and has only one scale...volts. The 1040 Fc was measured with the adapter on the 200Fc scale. With the adapter on the 2000Fc scale the meter reads 104.0 Fc and with the adapter on the 5,000 Fc scale the meter reads 10.4. Multiply the 2000 scale by 10 and it equals the 200 scale and if you multiply the 5,0000 scale by 100 it equals the 200 scale.

 

[aso]

PaulW

I stand corrected

Roy

I still don't understand how you get a reading of 1040 Fc on a 200 Fc scale