Vintage Western Instruments Foot lambert meter?

[danrogers]

Hi all. I have acquired a Western Instruments Inc. foot lamberts meter. I have no idea how it works, and google does not return much on it.

I guess its might be more used for photography?

could anyone shed some light on this device?

View attachment 66797

 

[cowboybob]

Most often used (with a light sensor attached) to determine the relative "brightness" of a movie projection screen and/or a CRT (TV, radar or other) screen.

Probably best used as a museum piece or to scavenge the, no doubt, high quality (50 to 100 uA) meter from it.

 

[crutschow]

It needs a light sensor matched to the meter. Do you have that?

 

[danrogers]

Hi guys.

No I sadly don't have any other parts for it So essentially its just a amp meter? But a very low current one? What would the light sensor look like?

Thanks

 

[crutschow]

The light sensor would likely be a small round or square device with a black bakelite case and one side having a glass opening with an area type photovoltaic light sensor such as selenium. You could use a small solar cell to test the meter but it wouldn't be calibrated, of course.

 

[danrogers]

I will have a look but its more than likely been thrown out, I was lucky to salvage the meter itself

I wonder what kind of operating current is required?

 

[alec_t]

I wonder what kind of operating current is required?

As stated in post #2, probably 50uA or 100uA for the meter movement. But the movement may have a shunt to adjust the sensitivity. Can you test it, e.g. with a PP3 and a 1Meg resistor?

 

[crutschow]

You can try checking it with an ohmmeter. Start at the highest range and work down. Note that the typical ohmmeter current is such as to give 200mV across the unknown at full scale.

 

[danrogers]

Thanks all. I don't really have the time or the incentive to fiddle too much so might just offer it for sale to be honest. Nice looking piece of equipment though