Integrating Sphere

© Brooke Clarke 2019

4" Sphere
        4" Sphere & 1" Ports
        Port Filters
Labsphere ISP-4000
LabSphere SC-5000
PVC Integrating Sphere


When Edison was working on the electric light he was concerned about the total light output and comparing that to a kerosene lantern or some other light then in use.  To do this he used an integrating sphere (Wiki).  The idea is that light will bounce around inside the sphere (painted a very reflective white on the inside) and in the process integrate all the light.  A sensor is also in the sphere, but there is no direct path from the light source to the sensor. Lumens (Wiki) is the common measure for light.  The light actually falling on a subject is measured in Lux (Wiki) where a Lux is 1 Lumen per square meter.  Lux varies from 0.0001 (overcast night sky) to 100,000 Direct Sunlight.  Also see Star Magnitude.  A prior unit for measuring the light falling on a surface was the Candlepower (Wiki).

Flashlights are commonly rated based on their total Lumen output.  But that does not tell you much since that light may be spread over a hemisphere like from a camping lantern or focused into a sharp beam.

I started this web page because I want to measure the light output from a bunch of flashlights that all use a AA battery, so hopefully this 4" sphere will work.

Sphere Description

A sphere may be made in two parts that are bolted together using a flange.  That allows coating the inside surface with something very white.

They also have a number of "ports" so that light can enter the sphere, for various types of photo sensors and maybe one or more standard light sources for calibration.

4" Sphere

Each hemisphere has 3 ports.  One at the top center and two additional ports down 45 degrees and these are seperated by 90 degrees.  One of the top ports is empty (input?) the opposite top port is plugged.
The other 4 ports have some type of electro optical gadget installed with a 4 socket connector.

Hand written labels on Sphere ports:
Yellow Temporal
Yellow Avg. Power
Green Temporal
Green Avg. Power

Port pinch hex set screws are 4-40 thread and 0.050" hex wrench.


Maybe Silicon Detector Assemblies: SDA-50-U
Detectors web page - Datasheet - mentions 1.2" standard port, so newer than this integrating sphere.

Black Connector Plate

Body diameter is 0.990".
Allen screws on connector plate: 3/32"
The ports on the integrating sphere have a lip to prevent the sensor from falling inside (see Fig 1 and Fig 2) where the hole in the lip is 0.750" dia.
Lemo connector.  mating shell may be FGG.0B.304.CLAD52.
00 multipole B
Insert configuration: 304
Series: 0B-0K-0T
See Fig 4 below.

the LEMO connector in the sensor is a EG (0, O, C, G, Q) ??B
the sensor PCB is p/n 87-1062-14 Rev A.

EG&G FND-100

Thor Labs photodiode overview (but not the FND-100).
Hamamatsu Silicon Photodiodes.pdf 
The TO-5 package (Wiki) body 5/16" dia (the flange has been ground down eliminating the tab.  This package supports between 2 and 10 leads.
The TO-5 to 3/4" gap filler part is black metal.
3 leads: Anode, Cathode & Case.
5.1 sq mm area.
100 V reverse bias typical.
1% linearity over 7 decades
400 to 1150 nm spectral response, peaks around 900 nm.

Sensor Wiring


2 & 3
Black &
B Shield


The voltage output on pins 1 and 4 is near zero when it's dark and goes up to hundreds of mV with bright light (EA4 Flashlight 860 Lumens).
The BNC and MS connectors seem to have the same signal, so maybe for different photometer models?
The SC-5000 has BNC inputs.

There is a capacitor (CK05BX 103K  0.01uF) and a resistor (1003F  100k) in addition to the EG&G FND-100 with date code 8814A (1988 week 14)

Pin 1: to 100k resistor then to Terminal X of FND-100.  The 0.01uF cap is between terminal X and ground (pins 2 & 3) = white wire
Pins 2 & 3 to body of FND-100. =coax shield & black wire
Pin 4: to terminal Y on FND-100 = coax center conductor

Orange Connector Plate


Has 1003F with CK05BX 103K CAP AND 511K resistor with CK05BX 223K capacitor.
The TO-5 to 3/4" gap filler part is white plastic.
This sensor has a very dense neutral density filter fitted that does not want to come off.

Pink Connector Plate


The TO-5 to 3/4" gap filler part is white plastic.
2 resistors & 2 caps - maybe different wiring?
In the bag with this sensor was an Orange (UV?) filter 0.500" dia x 0.120" thk
5.1 sq mm area
400 to 1150 nm resposnse
0 to 180 Volts
3 leads: Anode, Cathode & Case
4 pF (100V) compared to 8.5 pF (90V)  for the FND-100 so faster.

Sensor Output

Sensor numbering as shown in Fig 11 below.  Measured with FLuke 87 V DMM on mVDC range.

Black (-) & White (+)
Coax shield (-), Center (+)

* Jumps to -39 (80 L) then drifts back to -0.2
No. 4 seems to be dead.  That may account for thinking there was a cable problem.
No. 1 has a dense filter installed hence the lower readings for room and bright light.

Port Filters

These fit between the sensor and the 3/4" hole at the bottom of the port.  They have a 3/4" male nose and a 3/4" female tail that accepts the nose of the sensor.
That means you can stack them.  The tip of the nose is white.  There is no groove for a snap ring.  The snap ring is a friction fit inside the 1/2" filter cavity.


Both cables have electrical problems.  Sensor 4-pin connector marked: LEMO FHG 0B.  See Fig 10.
The cable with wire ends has the male pins inside the LEMO connector set way too far back, i.e. they are not plugging into the sensor.  Not the case, just different male pin lengths.
The cable with BNC and MS connectors has opens or shorts.  Need to test . . .   The bare wire end cable works fine.  More LEMO connectors on order (FGG 0B).

Sphere Photos

Fig 1
4" Integrating Sphere
Fig 2 The 4-40 set screws take a 0.050" hex wrench.
4" Integrating Sphere

Fig 3 Sensor + 2 cables.
One cable has4-pin LEMO FHG-0B to 3-pin MS3116F8-3P connector & BNC-m
Other cable only has 4-pin Lemo and wire ends.
Black & White wires & Coax shield + Center conductor.
4" Integrating Sphere
Fig 4 Sensor Connector
4" Integrating Sphere
Fig 5 Plug has cone shaped white end.
4" Integrating Sphere
Fig 6 Opened Sensor
4" Integrating Sphere
Fig 7 FND-100
4" Integrating Sphere
Fig 8 Filter Module
4" Integrating Sphere
Fig 9 Problem with LEMO pin protrusion
left: down 4.85mm
Right: down 2.93mm
4" Integrating Sphere
Fig 10 Probably not a problem
The pin insert shown protrudes 7.6mm.
The protrusion on the other cable is 9.6mm, i.e. longer pins.
4" Integrating Sphere
Fig 11 4 Sensors & Filter Housings w/sensors numbered.
4" Integrating Sphere

Labsphere ISP-4000


I'm guessing this was made to work with 1" ports since the sensor is 1" in diameter.  I expect the nose to be 3/4", waiting for it to get here.
ISP:   Integrating Sphere Photometer

Labsphere SC-5000 Integrating Sphere System Control


SC: Sphere Controller

This appears to be a general purpose light meter and maybe a power supply or switch for calibration light sources.  There are 3 input channels for:

Front Panel

Power Push On/Off & LED
LCD Guessing 2x40 characters
Buttons: Functions: Cal & Options, Data Adjust: Zero & Norm, Range: Up, Down, Auto
Talk, Listen & Remote LEDs

Fear Panel

Has three BNC jacks.  They have floating shields. i.e. each shield is independent of the other shields and chassis ground.
Channel 1
Silicon or Germanium diodes operated in photovoltaic mode (i.e. diode generates voltage/current) best measured as current into a virtual short. Diode- to center pin.
5 relays
Channel 2
Thermopile, Lead-Sulfate, PMT;
One Relay
Channel 3
Lead-Sulfide Bias Voltage (84 VDC bias, + on center conductor.)
No relay.

Digital Output Control
Now only single bit output to a 3/32" (2.4mm) plug

Remote Control
RS-232 Remote control DB-9
IEEE-488 Remote Control.


There are 3 BNC-f inputs on the back panel but there does not seem to be any way to select which is used on the front panel. Guessing that only one of the three can be used at any one time so no need to select.

It is not clear what types of sensor and how it is wired to the SC-5000.  Also what bias mode is used for the Silicon diode.
If you know about operation or have a manual please let me know.

Coax cable center: red coax in center
Black cable: black coax input shield
display shows current that varies with input (Cal1: Amps mode).
+0.124E-5 Amps room light
+0.605E-3 Terralux 100 flashlight

Fig 1 Front
Labsphere SC-5000
                      Integrating Sphere System Control
Fig 2 Back
Labsphere SC-5000
                      Integrating Sphere System Control
Fig 3 Inside Top
Power Supply upper center
Analog input- digital output lower right
Note three different channels of input.
Digital & front panel on left.
Labsphere SC-5000
                      Integrating Sphere System Control


Did not find any patents for the integrating sphere itself, only patents that use one to accomplish some task.


Hilger & Watts Spectrometer D 186.3/290
Light Meters
Optical Spectrum Analyzers 

PVC Integrating Sphere

YouTube: How to measure Flashlight Lumens and Candela using ANSI/NEMA FL1 standards -
YouTube: DIY Lumen Measuring Device. Integrating Shpere, and Lumen Tube - Styrofoam picnic box, (10:09) Lumen Tube (PVC) - reminder about temperature. -Internet Lumens vs Actual Lumens -


Budget Light Forum (BLF) - Texas_Ace integrating PVC sphere with no math involved -
Candle Power Forums - Estimate Lux & Lumens with Light Meter? LumenToob -


Johnny Mac Reviews -
Advanced Knife Bro - Flashlights - Moonlight and Firefly Modes on Flashlights. What those about? -


Edmund Optics - General Purpose Integrating Spheres - 2", 4" (has 1" ports) & 6" - Accessories -
Gamma-Sci - Integrating Spheres
Instrument Systems - Integrating Spheres - 3", 6", 12" and larger
LabSphere - Integrating Sphere Theory & Design.pdf - Integrating Spheres - The Light Measuring spheres range for 1.4 to 2 meters ID.  The Reflectance/Transmittance spheres are all 6" ID with a larger than normal port for the sample.  General Purpose includes a number of 4" ID spheres. These come with either 3 or 4 ports located in different places.
Light-Measurement - Tutorials On Light Measurement.pdf - III.1.a Integrating Sphere
Newport - Integrating Sphere Fundamentals and Applications - Port plugs come in sizes: 1/2", 1", 1-1/2", 2,5"
SPIE - Field Guide to Illumination - Integrating Sphere -


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