
Test Equipment Depot - 800.517.8431 - 5 Commonwealth Ave, Woburn MA 01801
H.
Paperless Humidity/Temperature Chart Recorder
USER MANUAL
Model RH520B
1%
mal
DD
8
�
tc=3B PM
EXTECH.
0�. Y
1 J
I
ID- 16- IY
5n%
I
-
�
0�
-
O
CE

Introduction
Changes or modifications not expressly approved by the party responsible for compliance could void the
user's authority to operate the equipment.
Congratulations on your purchase of the Extech RH520B Temperature + Humidity Chart
Recorder. The RH520B measures and displays Temperature, Humidity, and Dew Point.
The remote (detachable) probe senses the ambient conditions while the LCD display graphs and
provides numerical representation of the readings. Programmable audio-visual alarms alert the
user when ambient conditions reach alarm presets. The optional alarm module permits
automatic relay switching when alarm presets are reached.
The RH520B Internal Memory can store up to 49,152 measurements for later transfer to a PC.
Careful use of this instrument will provide years of reliable service.
CAUTIONS
This device is not a toy, it contains hazardous objects as well as small parts that children can
swallow. Contact a physician immediately if an object is swallowed.
Do not leave batteries or packing material unattended; they can be dangerous to children.
If the device is to be unused for an extended period, remove the batteries to prevent them
from draining.
Expired or damaged batteries can cause cauterization on contact with the skin. Use
protective gloves when necessary.
Do not short-circuit batteries or discard them in a fire.
FCC Compliance
This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to
part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful
interference in a residential installation. This equipment generates, uses, and can radiate radio frequency
energy and, if not installed and used in accordance with the instructions, may cause harmful interference to
radio communications. However, there is no guarantee that interference will not occur in a particular
installation. If this equipment does cause harmful interference to radio or television reception, which can be
determined by turning the equipment off and on, the user is encouraged to try to correct the interference by
one or more of the following measures:
1. Reorient or relocate the receiving antenna.
2. Increase the separation between the equipment and receiver.
3. Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
4. Consult the dealer or an experienced radio/TV technician for help.
2 RH520B-en-US_v5.2 8/20

DISPLAY DESCRIPTION
2
3
4
3
5
6 7 8
9
9
10
11
9
12
MAX
MIN
ALARM
MAX
MIN
SET
DEW POINT
1. Temperature measurement graph
2. Internal memory usage meter
3. Vertical axis scale limits
4. Cursor / Alarm indicators
5. Push-button lock-out status indicator
6. Time display
7. Relative Humidity (RH) measurement graph
8. Date display
9. Function indicators
10. Numerical temperature reading display
11. Numerical RH reading display
12. Battery status indicator
4 RH520B-en-US_v5.2 8/20

PUSH-BUTTON DESCRIPTION
VIEW Return the LCD to the Standard View
Escape from any setting function without storing value changes
Scrolls highest and lowest (MAX/MIN) readings when in Standard View
ALARM Display or Set alarm values
TIME Display a reading stored at specific Time and Date
Set and Display the recording Sampling Rate
Set the Time and Date
SET Used in combination with other buttons to set new parameter values
Stores new parameter values and returns to the Standard View
TEMP Used in combination with other buttons to set the vertical graph range
Used in combination with other buttons to set temperature alarm values
Used in combination with the RH button to display Dew Point
RH Used in combination with other buttons to set the vertical graph range
Used in combination with other buttons to set RH alarm values
Used in combination with the TEMP button to display Dew Point
Right, left, down, and up arrow buttons for scrolling data and navigating the
display
Test Equipment Depot - 800.517.8431 - 5 Commonwealth Ave, Woburn MA 01801
5 RH520B-en-US_v5.2 8/20

KEYPAD QUICK REFERENCE (ALSO SHOWN ON REAR OF THE RH520B HOUSING)
Second / Alternate Keystrokes
VIEW modes: Normal, TEMPmax,
RHmax, TEMPmin, RHmin
VIEW to cancel, exit mode
Scroll through selections
Movers cursor through stored
points
View reading at specific
time/date
Arrow keys to select, VIEW to
exit
Step back through ALARM
points
ALARM selects next Alarm, VIEW
to exit
Enters Set TEMP Alarm mode
ALARM selects HIGH/LOW, SET to
save
ALARM selects HIGH/LOW, SET to
save
Enter Set Sample Rate mode
SET to save, VIEW to exit
SET to save, VIEW to exit
Enter Set TEMP Vertical Scale
mode
TEMP selects upper/lower, SET to
save
Enter Set RH Vertical Scale
mode
RH selects upper/lower, SET to
save
6 RH520B-en-US_v5.2 8/20