YOKOGAWA 51011 User manual

User’s
Manual 51011, 51012, 51021
Digital Lux Meter
IM 51011-01EN
4th Edition: Oct. 2017 (YMI)
Store this manual in an easily accessible
place for quick reference.

IM 51011-01EN 1
Introduction
Thank you for purchasing the digital lux meter.
This user’s manual primarily explains the handling precautions and
basic operations of the digital lux meter.
To ensure correct use, please read this manual thoroughly before
beginning operation.
After reading this manual, keep it in a safe place.
List of Manuals
The following manuals, including this one, are provided as manuals
for the digital lux meter. Please read all manuals.
IM 51011-01E User's Manual (this manual)
IM 51011-93Z2 Document for Korea
Contact information of Yokogawa offices worldwide is provided on
the following sheet.
PIM 113-01Z2 Inquiries List of worldwide contacts
Notes
• The contents of this manual are subject to change without prior
notice as a result of continuing improvements to the instrument’s
performance and functionality. The figures given in this manual
may differ from the actual screen.
• Every effort has been made in the preparation of this manual to
ensure the accuracy of its contents. However, should you have
any questions or find any errors, please contact your nearest
YOKOGAWA dealer.
• Copying or reproducing all or any part of the contents of
this manual without the permission of YOKOGAWAis strictly
prohibited.

IM 51011-01EN
2
4th Edition: October 2017 (YMI)
All Rights Reserved, Copyright ©
2013, Yokogawa Meters & Instruments Corporation,
2017, Yokogawa Test & Measurement Corporation
Printed in Japan
Trademarks
• Adobe, Acrobat, and PostScript are either registered trademarks
or trademarks of Adobe Systems Incorporated.
• In this manual, the ® and TM symbols do not accompany
their respective registered trademark or trademark names.
• Other company and product names are registered trademarks
or trademarks of their respective companies.
Revisions
• February 2013 1st Edition
• October 2013 2nd Edition
• May 2013 3rd Edition
• October 2017 4th Edition

IM 51011-01EN 3
Checking the Contents of the Package
Unpack the box and check the contents before operating the
instrument. If the wrong items have been delivered, if items are
missing, or if there is a problem with the appearance of the items,
contact your nearest YOKOGAWAdealer.
Digital Lux Meter
Check that the product that you received is what you ordered by
referring to the model name on the name plate.
MODEL Specifications
51011 JIS Class A
Measurement ranges: 99.9/999/9,990/99,900/999,000
51012 JIS Class AA
Measurement ranges: 99.9/999/9,990/99,900/999,000
51021 JIS Class AA
Measurement ranges:
9.99/99.9/999/9,990/99,900/999,000
51011, 51012: Single-function model
Compliant standard: JIS C 1609-1: 2006
(JIS: Japanese Industrial Standards)
Standard Accessories
AA-size alkaline batteries 2
Recorder output plug (JC017A) 1
Soft-sided case (RB038A) 1
User’s Manual (Japanese and English) 2
Optional Accessories (Sold separately)
Item Specifications Model
Light-detector extension
cable 3 m 91001
30 m 91002

IM 51011-01EN
4
Conventions Used in This Manual
Notes and Cautions
The notes and cautions in this manual are categorized using
the following symbols.
Improper handling or use can lead to injury to
the user or damage to the instrument.
This symbol appears on the instrument to
indicate that the user must refer to
the user's manual for special instructions.
WARNING
Calls attention to actions or conditions that
could cause serious or fatal injury to the user,
and precautions that can be taken to prevent
such occurrences.
CAUTION
Calls attention to actions or conditions that could
cause light injury to the user, or cause damage
to the instrument or user’s data, and precautions
that can be taken to prevent such occurrences.
Note Calls attention to information that is important for
the proper operation of the instrument.

IM 51011-01EN 5
Safety Precautions
This product is designed to be used by a person with specialized
knowledge.The general safety precautions described herein must
be observed during all phases of operation. If the instrument
is used in a manner not specified in this manual,
the protection provided by the instrument may be impaired.
This manual is an essential part of the product; keep it a safe
place for future reference.
YOKOGAWA assumes no liability for the customer’s failure to
comply with these requirements.
The following symbols are used on this instrument.
Warning: handle with care.
Refer to the user’s manual or service manual.
This symbol appears on dangerous locations on
the instrument which require special instructions for
proper handling or use.
The same symbol appears in the corresponding
place in the manual to identify those instructions.
Make sure to comply with the precautions below.
Not complying might result injury or death.
WARNING
Use the instrument Only for Its Intended Purpose
The lux meter is for measuring illuminances.
Do not use this meter for any other purpose.
Check the Physical Appearance
Do not use the meter if there is a problem with its physical appearance.
Do Not Disassemble
Only qualified YOKOGAWApersonnel may disassemble this product.
Do Not Operate in an Explosive Atmosphere
Do not use this meter in the presence of flammable gases or vapors.
Doing so is extremely dangerous.

IM 51011-01EN
6
CAUTION
• The meter is for domestic use (Class B) and meets the
electromagnetic compatibility requirements.
• Do not drop the meter or strike it against hard objects.
• Avoid storing the meter in direct sunlight or in a humid environment.
• Using the meter in an low-temperature environment (–10°C to 0°C)
may slow down the display’s response.
• Avoid using the meter in a dirty or dusty environment or
in an environment with salt or corrosive gases.
• Do not wipe the meter with organic solvents.
Dirt or dust adhering to the light-detecting surface of the meter
decreases measurement accuracy.
Wipe the surface clean with a soft, dry cloth.
• Do not separate the light-detector from the main unit with
the power on.

IM 51011-01EN 7
Measurement Category
WARNING
• Do not use the meter for measurements in locations falling
that fall under Measurement Categories II, III, and IV.
• Do not use the meter to measure voltage or current.
The meter is designed for measurement category I:
EN 61010-1: 2001
Measurement
Category Description Remarks
CAT I
For measurement performed on
circuits not directly connected to
MAINS.
CAT I: EN 61010-1: 2001
Circuits not connected
to a mains power
source.
CAT II For measurement performed on
circuits directly connected to
the low-voltage installation.
Appliances, portable
equipment, etc.
CAT III For measurement performed in
the building installation. Distribution board, circuit breaker, etc.
CAT IV For measurement performed at
the source of the low-voltage
installation.
Overhead wire,
cable systems, etc.

IM 51011-01EN
8
Contents
Introduction.............................................1
Checking the Contents of the Package .......................3
Conventions Used in This Manual ...........................4
Safety Precautions .......................................5
Measurement Category ...................................7
1. Component Names and Functions........................9
2. Before Operation ....................................14
2.1 Measurement Functions ..........................14
2.2 Turning the Power On and Off......................14
2.3 Setting the Response ............................15
2.4 Checking and Replacing Batteries ..................16
2.5 Automatic Power Off .............................16
2.6 Notes on Illuminance Measurement .................18
3. Normal Illuminance Measurement .......................19
4. Color Correction Measurement (K Key) ...................20
5. Timer Hold (HOLD and T-H Keys) .......................22
6. Range Hold (RANGE Key) .............................24
7. Average Illuminance (AVG Key).........................25
8. Deviation Display (Δ/% Key)............................27
9. Light Source Luminous Intensity (cd Key) .................28
10. Totalized Intensity of Illumination
(ACC Key) .........................................29
11. Comparator (COMP Key)..............................32
12. Ripple Measurement (S-F Key) .........................33
13. Communication Functions .............................36
13.1 Cable Connection and Interface Specifications.........36
13.2 List of Commands ...............................37
13.3 Detailed Description of Commands..................38
14. Recorder Output (Analog Output) .......................41
15. Separating the Light Detector...........................42
16. Supplying Power through USB ..........................42
17. After-Sales Service...................................43
17.1 Error Messages .................................43
17.2 Calibration .....................................43
18. Specifications .......................................44
19. Characteristics of Relative Visible-
spectrum Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
20. Characteristic of Oblique Incident Light ...................51
21. Illuminance Measurement Method .......................52
22. For the Pollution Control of Electronic
and Electrical Products of the People's Republic of China.....55

IM 51011-01EN 9
1. Component Names and Functions
Light-detecting surface
Display
Main unit
Hand strap
Keys
Cap
Protects the
light-detecting surface
Used also during
automatic
zero adjustment
Light detector
Can be separated
from the main unit
(using an extension
cable)
USB port
(mini B type)
Use the USB cable
to communicate to the PC
and supply power.
POWER key
Turns the power
on and off

IM 51011-01EN
10
Keys
POWER
ON/OFF RANGE
T
- H CALL
Δ / %
1 K
2 AVG
COMP
3 c d
4 ACC
C
SET S
- F
>
POWER
ON/OFF RANGE
T
- H Δ / %
51021 51011/51012
(single-function model)
RANGE Key
Use this key to switch the range.
Press the key to switch to manual range mode.The range changes
each time you press the key.To return to auto range mode, hold the
key down for at least 1 second.
T-H Key
Use this key to set the timer hold-time or start the timer.
CALL Key
Use this key to view settings.
Values (shown below) that are relevant to the measurement
function that you are using are displayed while you hold the key
down.
Color correction factor, intensity measurement distance, high and
low comparator limits, and ripple ratio
Δ/% Key
Use to display deviation.
Press the key to display the deviation or percentage of
measurement data in reference to a reference value.
To return to the normal luminance measurement,
hold the key down for at least 1 second.
K Key
Use this key in color correction measurement.
Color corrected results are displayed.
A switch is made between normal measurement and color
correction measurement each time you press this key.
You can also set the color correction factor.

IM 51011-01EN 11
AVG Key
Use this key in average illuminance measurement.
To return to the normal illuminance measurement, hold the key
down for at least 1 second.
1, 2, 3, 4, and C Keys
Use this key in average illuminance measurement.
You can store location data for the 4-point method and 5-point
method.
(Location number display:
12 3 4C
)
COMP Key
Use this key to set the high and low comparator limits and to start
the comparator function.
To return to the normal illuminance measurement, hold the key
down for at least 1 second.
cd Key
Use this key to set the light intensity distance and to display the
intensity.
A switch is made between normal measurement and light source
intensity measurement each time you press the key.
ACC Key
Use this key to set the limit for the totalized intensity of illumination
and to display the integral time and integral value.
To return to the normal illuminance measurement, hold the key
down for at least 1 second.
S-F Key
Use this key in ripple measurement.
A switch is made between normal measurement and ripple
measurement each time you press the key.
SET Key
Use this key to configure various settings.
Key and Key
Use these keys to move the setting position and change values.

IM 51011-01EN
12
Tripod-mounting screw
Measurement reference
plane indication
Battery cover
Hold switch
Holds the measured
data reading
Response selector
switch
Switches the light
detector response speed
between FAST and SLOW
Eject button
Used to separate
the light detector
from the main unit
Recorder output
connector
Connect to a
recorder or
oscilloscope with
a dedicated
cable.

IM 51011-01EN 13
Display
1 2 3 4C S F
AVG MEMO RSPS
AUTO POWER OFF COMP
RCD Go HiLo
CALL SET KS-F R-H D-H
fc S
lx h
%m
cdft
*: When every element is showing (some elements are not used)
Element Description
8,8.8.8,8.8.8 Digital display of measured, calculated, and set values
AUTO POWER OFF Lights in automatic power-off mode
Deviation
CALL Lights when CALL is pressed
SET Lights in setting mode
KColor correction factor
RCD
Lights when a plug is inserted into the recorder output
connector
S-F Ripple measurement
Lo Go Hi
COMP
Lights in comparator mode
R-H Lights in range hold mode
D-H
Lights in data hold and timer hold modes
Lights when the battery voltage is low
1 2 3 4 C
AVG-MEMO-
Lights during average illuminance
S F
RSPS
Response setting
STimer hold-time unit (seconds)
lx Unit for illuminance measurement
hUnit for integral time of totalized intensity of illumination
%Deviation display %
mUnit for the distance to the light source
cd Unit for luminous intensity; lights during light source
luminous intensity measurement

IM 51011-01EN
14
2. Before Operation
2.1 Measurement Functions
The meter has the following measurement functions.
51011 Single-function model
• Normal luminance measurement
• Deviation display
51012
51021
• Normal luminance measurement
• Deviation display
• Color correction luminance measurement
• Average luminance measurement
• Comparator function
• Light source luminous intensity measurement
• Totalized intensity of illumination
• Ripple measurement
Only the color correction function can be used in combination with
another function. Operation of other measurement functions are
not allowed except for the normal luminance measurement and
color correction measurement screens.
2.2 Turning the Power On and Off
CAUTION
Check that the meter operates normally.

IM 51011-01EN 15
Cover the light-detecting surface with the cap, and press the
POWER key to turn on the meter.
The initial display appears.
All the LED elements will light, and [--CAL--] will appear
(automatic zero-adjustment mode). Then, the display shows the
luminance measurement [0.00 lx] display.
([0.0 lx] appears on Model 51011 and 51012.)
If you press the POWER key again, the meter will turn off.
(See chapter 3, “Normal Illuminance Measurement,” and
section 17.1, “Error Messages.”)
2.3 Setting the Response
You can set the response speed of the light detector with the
response selector switch.Set the switch to FAST or SLOW
according to your application.
Switch
position Response speed Application
FAST Approx.
10 ms Measurement of continuous light such as daylight and interior lighting (fluorescent lamps,
incandescent lamps).
The display shows [RSPS F ].
SLOW Approx.
500 ms Measurement of the average illuminance of
flickering lights or a light that varies over time
such as that from a TV screen.
The display shows [RSPS S ].
Note
If the recorder output is used for waveform observation, set the
switch to FAST.

IM 51011-01EN
16
2.4 Checking and Replacing Batteries
When the battery voltage drops, the display area shows a
[ ] mark. When this mark appears, replace the batteries
with new ones.
Turn off the power, and remove the battery cover.
Check the polarity markings, and insert the new batteries in
the correct orientation. Close the battery cover completely.
Battery type: Two AA dry cells
Battery
Main unit
Battery cover
2.5 Automatic Power Off
The meter has an automatic power-off function to prevent
unnecessary battery usage when you forget to turn off the power.
If there is no key activity for about 30 minutes, the meter beeps
twice and automatically turns off.
Pressing any key while the meter is beeping extends the time
until the power turns off for another 30 minutes.
The automatic power-off function is disabled while the totalized
intensity of illumination or comparator function is being executed
or when a plug is inserted in the recorder output connector.
When the automatic power-off function is enabled,
[AUTO POWER OFF] is displayed.

IM 51011-01EN 17
Releasing the Automatic Power-Off Function
Cover the light-detecting surface with the cap.
Press the HOLD switch (HOLD switch lock) and then the
POWER key to turn on the power.
After the initial display, [AUTO POWER OFF] disappears and the
automatic power-off feature is released.
Press the HOLD switch again to release the HOLD state (lock),
and perform measurements.
Reverting the Automatic Power-Off Function
Press the POWER key to turn the power off.
Cover the light-detecting surface with the cap.
(Check that the HOLD switch is not locked.)
Press the POWER key again to turn on the power.
After the initial display, [AUTO POWER OFF] appears,
and the automatic power-off function returns.

IM 51011-01EN
18
2.6 Notes on Illuminance Measurement
To make accurate measurements, note the following items.
• Before starting measurement, turn on the light bulb 5 minutes
and the discharge lamp 30 minutes beforehand.
• Set the position and angle of the light-detecting surface
accurately.
The measuring reference plane is shown below.
EJECT
35 mm
Measurement reference plane
• Be careful that measurements are not affected by where you
are and what you are wearing.
• For accurate measurements, perform color correction with
a color correction factor that corresponds to the spectral
distribution of the light source under measurement and the
relative spectral response of the meter.
The meter has color correction factors for typical light sources.
You can also register up to 21 correction factors that you can
use for color correction. (See chapter 4, “Color Correction
Measurement”).
• When you measure for long period of time, the zero point may
change due to large changes in the ambient temperature.
In such a case, turn off the power once and then turn it on
again. (See the procedure in chapter 3, “Normal Illuminance
Measurement.”)

IM 51011-01EN 19
3. Normal Illuminance Measurement
Automatic Zero Adjustment
1. Cover the light-detecting surface with the cap.
(Check that the HOLD switch is not locked.)
2. Press the POWER key to turn on the power.
After all the elements light, automatic zero adjustment is
executed ([--CAL--] is displayed).
When the adjustment is finished, [--CAL--] disappears.
(Initial display end)
The illuminance measurement [0.00 lx] display appears.
([0.0 lx] appears on Model 51011 and 51012.)
Note:
If the [--CAP--] display persists, the cap may not be on
correctly. Put the cap on correctly. (The cap may be broken.)
Starting to Measure
3. Remove the cap, and start measuring.
F
RSPS
AUTO POWER OFF
lx
4. When you are finished measuring, press the POWER key
to turn off the power. Cover the light-detecting surface for
protection.
Note:
If [Err] appears during measurement, check that the light
detector is connected correctly to the main unit and that the
cap is off, and then start from the beginning.
(See section 17.1, “Error Messages.”)