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RH31
Ha nd he ld Te m p e ra ture /
Hum id ity Ind ica tor
M3185/ 1098
N O TES
TABLE O F CO N TEN TS
RH3 1 Hu m id ity / Te m p e ra tu re Me te r
SECTION
SECTION
1
2
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
UNPACKING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
SECTION
3
ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1 Battery Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2 RH31 Indicator Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3 How to Switch From ˚ F to ˚ C . . . . . . . . . . . . . . . . . . . . . . . . . . 5
SECTION
4
OPERATING INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . .. 6
4.1 Display Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2 RS232 Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.3 Key Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
SECTION
SECTION
5
6
HUMIDITY CALIBRATION . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1 5
i
SECTIO N 1 IN TRO DUCTIO N
SECTIO N 6 SPECIFICATIO N S
The OMEGA® RH31 Handheld Temperature/ Humidity Indicator has broad
applications in air conditioning services, food management, process engineering,
and many uses in experimental and research facilities.
RH31 METER
Measuring range:
Temperature: -10 to 60˚ C
Relative humidity: 0 to 100% RH
Accuracy rating:
Temperature: ±(0.1% of measured value +0.2˚ C)
Relative humidity: ±(0.1% of measured value +0.2% RH)
Dew-point temperature: ±1.0˚ C
The built-in digital display is accurate to ±0.6˚ F (0.3˚ C) and ±3% RH, and reads
out in either degrees F/ C.
Wet-bulb temperature: ±0.8˚ C
(at temperature 25˚ C and relative humidity 50% RH)
Three probe types are available for use with the RH31 and all are interchangeable
through a connector located on the RH31 Indicator:
Temperature
Temperature: ±(0.2% of measured value +0.1˚ C)
coefficient (per 10˚ C): Relative humidity: ±(0.2% of measured value +0.1% RH)
RH31-1 General Purpose Probe for Laboratory and Warehouses
RH31-2 Thin Type Probe for Tanks and Narrow Gaps
RH31-3 Remote Mounted Probe with Cable
Display:
31/
digits LCD (Liquid crystal) digital display
2
Temperature, relative humidity, dew-point temperature,
wet-bulb temperature, unit, battery shortage mark
The ultra sensitive composite sensor element in the probes is composed of a
temperature and humidity sensor formed into a single unit. The humidity sensor
is an electrostatic capacitance type polymer-film, and the temperature sensor is a
platinum resistance RTD.
Resolution:
Temperature: 0.1˚ C/ 0.1˚ F
Relative humidity: 0.1% RH
Memory function:
Data: 1500 data each of temperature and humidity
Content: Temperature, humidity
Measurement Time Interval: 10-minute
A calibration kit (part number RH30-CAL) is also available for recalibrating the
RH31 Indicator and RH31-1 General Purpose Probe.
Communications
Interface:
RS-232C
(with communication cable)
Obtain new sensor, if temperature/ humidity sensor has become defective. No
adjustment is necessary after exchange, because the sensor is interchangeable.
Working
temperature range:
0 to 50˚ C (32 to 122˚ F)
If the response time is delayed in the general type sensor, remove the cap from
the sensor tip, and remove the filter. (Screw in the cap as before after removing
the filter.) In this case, the sensor is apt to be contaminated with dust or the like,
and its service life may shorten.
Working
humidity range:
0 to 85% RH (no dew condensation is allowed)
Exclusive lithium battery 1 piece (7.2 Vdc)
Power Voltage:
Battery life:
Approx. 400 hours
(at normal temperature and humidity)
The battery assembled at the delivery time from the factory is used for test so that
its life may be shorter than the nominal value.
Weight:
Approx. 180 g (6.3 oz) (without memory function)
Approx. 190 g (6.7 oz) (with memory function)
Power auto-off function
A power auto-off function is provided and the battery life is longer than 400
hours in continuous use at normal temperature.
RH31 SENSORS
Measuring range:
Temperature: -10 to 60 ˚ C (14 to 140˚ F)
Relative humidity: 0 to 100% RH
The RH31-RS232 has a memory function and is also able to collect up to 1500
points of data (temp., humidity). The measuring interval is 10 minutes.
Accuracy rating:
Temperature: ±0.15˚ C (at 0˚ C), ±(0.15+0.002[t])˚ C,
t: Measured temperature (˚ C)
Relative humidity: ±3% RH (at 25˚ C, 0 to 90% RH)
Temperature-humidity sensor exchange
The temperature-humidity sensor is interchangeable, and it can easily be
replaced, if it has been broken or it has deteriorated.
Temperature
coefficient:
Relative humidity: ±1% RH (Reference 25˚ C, per 10˚ C)
Handling of temperature-humidity sensor
Handle this precise unit carefully so as not to drop or strike it, otherwise a trouble
may occur. This unit is not water-proof. Don’t dip it into water or moisten it.
Response:
Without filter: Approx. 1 minute (90% response)
With filter: Approx. 3 minutes (90% response)
Sensor element:
Temperature: Platinum resistance thermometer (JIS Class A)
Humidity: Capacitance type high polymer film
Cable length:
Standard 1m (3'), Maximum 5m (16')
Weight (with 1m
of cable):
RH31-1: Approx. 60 g (2.1 oz)
RH31-2: Approx. 70 g (2.5 oz)
RH31-3: Approx. 100 g (3.5 oz)
1
1 4
HUMIDITY CALIBRATION KIT
The OMEGA® RH30-CAL Humidity Calibration Kit is needed to perform the
humidity calibration of the RH31 Indicator and RH31-1/ RH31-2 Probe assembly.
The Calibration Kit consists of two salt chambers held in a styrofoam base. One
chamber contains a saturated salt solution of Lithium Chloride (to simulate 11%
relative humidity). The other chamber contains a saturated salt solution of
Sodium Chloride (to simulate 75% RH).
The RH31-3 cannot be field calibrated. No adapters are available.
INSTRUCTIONS TO DISASSEMBLE THE HUMIDITY PROBES
The potentiometer (pots) necessary for the humidity calibration procedures are
located in the RH31-1/ RH31-2 probes.
Each probe is slightly different, thus disassembly will vary. Perform the follow-
ing procedures while referring to the corresponding steps pictured in the Figure
for your particular probe type.
RH31 HUMIDITY/TEMPERATURE ADJUSTMENT
1. Please have RH30 Kit which OMEGA Engineering provide (30% RH).
2. Potential meter for adjustment is located about middle of handle portion of
probe. (Only 1 potential meter)
3. As on Fig. 3 and 4, remove label covering potential meter.
Re m o ve
La b e l
VR
Fig . 3 . RH3 1 -1 Pro b e
Re m o ve
La b e l
VR
Fig . 4 . RH3 1 -2 Pro b e
Fig u re 1 . RH3 1 a n d RH3 1 -1 , RH3 1 -2 , RH3 1 -2 Pro b e s
4. Enter probe to calibration kit.
5. Turn potential meter to meet calibration kit reading. Once display is same or
close to calibration kit, adjustment is done.
6. No calibration for temperature.
1 3
2
SECTIO N 2 UN PACKIN G
SECTIO N 5 HUMIDITY CALIBRATIO N
Remove the packing list and verify that all equipment has been received. If there
are any questions about the shipment, please call the OMEGA Customer Service
Department at 1-800-622-2378.
PRECAUTIONS
Due to its design, and ease of access, the humidity sensor must be handled with
care. AVOID ANY CONTACT with fingers, atmosphere, or products which
could be harmful to the sensor. The sensor must not come in contact with dirt or
other foreign material. Incorrect readings can be caused by build-up of material,
which can increase or decrease the RH reading.
Upon receipt of shipment, inspect the container and equipment for any signs of
damage. Take particular note of any evidence of rough handling in transit.
Immediately report any damage to the shipping agent.
During measurements, the following precautions should be taken:
N O TE:
1. When the temperature, at the location being measured, changes drastically,
allow at least 10 minutes for the measurement to stabilize.
The carrier will not honor any claims unless all shipping
material is saved for their examination. After examining
and removing contents, save packing material and carton
in the event reshipment is necessary.
2. The sensor response will vary greatly depending on the air flow in the vicinity
being measured, the heat capacity of materials surrounding the probe, and the
thermal conductivity. Alllowing for the response time of 30 seconds or so,
keep the probe at a distance from the body, when the probe is held in ones
hand, to eliminate the effects of body heat.
Please note that the following items are in the box:
RH31 INDICATOR:
3. Always turn the unit OFF after measurements are completed. When the meter
is not in use for extended periods of time, remove and store the battery.
RH31 Temperature/ Humidity Indicator
9 volt Battery
Transparent vinyl case for Indicator
Operator’s Manual
HUMIDITY SENSOR CLEANING
Use no solvents stronger than DISTILLED WATER to clean the sensors. If
necessary, rinse the sensors with distilled water, being careful not to touch it
with your fingers. After rinsing, the sensors should air dry for at least 24 hours
(prefereably over an air flow register).
RH31 PROBES (refer to Figure 2):
RH30-1, -2, -3, Humidity/ Temperature Probe
Plastic Bag to hold probe assembly
Operator’s Manual
DISPLAY CODES
-OVER: Measured values are displayed on the 31/
digit LCD. For temperatures
2
over 212˚ F (100˚ C) and humidity over 99.9%, the message “OVER” is displayed.
-BATT: When the battery is low, the message “BATT” appears on the display
and the batttery must be replaced.
HUMIDITY CALIBRATION
The RH31 Indicator and probes are calibrated at the factory and do not usually
need to be recalibrated. The warranty is void if the unit is tampered with while
still under warranty. Contact OMEGA Engineering for service information.
The following procedures are necessary only if the unit is operating out of speci-
fication and is no longer under warranty. These procedures should be performed
by a qualified technician.
Only the RH31-1 general purpose probe & RH31-2 can be field calibrated.
3
1 2
Fig u re 2 . Pro b e Asse m b lie s fo r th e RH3 1
Fig u re 1 . RH3 1 In d ica to r
1 1
4
SECTIO N 3 ASSEMBLY
3 .1 Ba tte ry In sta lla tio n
BATTERY EXCHANGE METHOD
4 .3 Ke y O p e ra tio n
Names of keys Contents
ON-OFF The power supply is turned on by pressing this key once and turned
off by pressing this key again.
1. How to open the case
The case can be opened by removing two screws on the rear panel of the case.
A confirmation chime sounds after turning on the power supply, and the power
supply turns off automatically after about 3 minutes.
For canceling the auto off function, press [ON-OFF] key together with [CLEAR]
key.
In this case, the case can be opened easily be pulling the hand strap in the open
direction, while pressing the upper case.
A confirmation chime sounds three times.
2. How to remove the battery
Insert a screwdriver to the bottom of the battery connector while holding the
battery connector by fingers, and disconnect the connector by pushing it upward.
For turning off the power supply, press [ON-OFF] key.
• CLEAR By pressing this key, a confirmation chime sounds, the display setting
functions (hold, humidity operation selection) are canceled, and the unit returns
to the initial condition.
3. Battery exchange
When the memory function is provided, (1) data collection is stopped by press-
ing this key halfway during data collection (2) data readout is stopped by press-
ing this key halfway during data readout, and also (3) the unit is reset to the last
settting by pressing this key halfway during the time setting.
• HOLD The measured values of temperature and humidity are held by press-
ing this key and the unit is set to the measuring condition (the hold condition is
canceled) by pressing this key once more.
Connect the battery connector to the connector on the PC Board. In this case, a
confirmation chime sounds to show the end of the exchange.
Never disassemble, short, charge, throw into a fire, or heat the used battery
nor directly solder it to the battery body, otherwise a rupture accident or an
electrolyte leak failure may occur.
4. How to close the case
During the hold of measured values, ˚ C(˚ F) flickers.
• SEL The indicating value is switched in the order of [relative humidity →
dew point → wet-bulb temperature].
Insert the battery cord to the guide of the upper case without protruding it out of
the case. Mount the hand strap.
Fit the upper and lower cases to each other and fasten two screws.
Relative humidity: %RH
Dew point: ˚C(˚ F)
Wet-bulb temperature: ˚C(˚ F) flickering
• READ Press this key for advancing the numeric stepwise when setting the
present time or data collection time.
Press this key when transmitting collection data to the personal computer.
• WRITE Press this key for switching the setting items such as year, month,
day, hour, and minute when setting the present time and data collection time.
3 .2 RH3 1 In d ica to r Asse m b ly
Slide the RH31 indicator into the vinyl case provided in order to protect the case
during use. Plug in the probe that is best suited for your application (see Figure 2
above for probe selection). The temperature/ humidity probes are plugged into
the socket located on the top of the indicator. Be sure to line up the “keys” on
each connector before plugging in the probe.
TROUBLESHOOTING
Symptoms Check contents
No display appears – Problem 1
Are the indicator and temperature-humidity sensor connected to each other
securely?– Check
Has the battery life come to an end? – Check
Is the battery set correctly? – Check
Display remains unchanged – Problem 2
Is the [HOLD] key pressed? (˚ C (˚ F) flickers in this case) – Check
Measured values are abnormal – Problem 3
[Is the unit correct?] – Check
3 .3 Ho w To Sw itch Fro m ˚F/ ˚C
1. Remove 2 back cover screws.
2. Jumper pins 1 & 2 for ˚C, pins 2 & 3 for ˚ F.
3. Put back lower case and tighten screws.
Co ve r
Scre w s
Bar display appears in the upper column. – Problem 4
[Over-range]
Bar display appears in the lower column – Problem 5
[Under-range]
˚ C
˚ F
5
1 0
4. Sample program
SECTIO N 4 O PERATIN G IN STRUCTIO N S
4 .1 Disp la y Co d e s
Prepare a data file in advance.
(1) In case of N88BASIC (A hard disc is used)
60 “232-C CIRCUIT”
(1) Connection joint:
110 ’DATA STORAGE
Connect the exclusive temperature-humidity sensor to top of unit.
(2) In case of N88BASIC (a floppy disc is used)
80 “232-C Circuit”
100 FOR A = 0 TO 50000!
‘’SELECT THE FINAL VALUE TO CONFORM TO PC.
200 DATA STORAGE
(2) AM/ PM indication Note):
Indicated when the present time or preset data collection time is set.
(3) Battery shortage indication:
The battery shortage mark lights when the battery life comes to an end.
(4) [ON-OFF] key:
220 IF 1=0 THEN PRINT
Turns on and off the power supply.
‘’COMMUNICATION IS IMPOSSIBLE”: END
The power auto-off function is reset by [CLEAR] key + [ON-OFF] key.
Communication Protocol for RH31-RS232C
(5) [HOLD] key:
Press this key when holding a measured value.
Start-Stop System
3 line system
Transmission Speed
Start bit
: Talk only
: 1200 bps
: 1 bit
(6) [READ] key Note):
Press this key when transmitting data to a personal computer.
(7) [WRITE] key Note):
Press this key when setting the preset time or preset data collection time or when
transmitting date to a personal computer.
Data Length
Stop bit
Character code
Data transmission
Procedure
: 8 bits
: 1 bit
: ASCII code
(8) Measured temperature value and unit:
Indicates the measured temperature value and unit (˚ C or ˚ F).
: Non-procedure
RH31-RS232C does not have any communication formats
because this output measuring data at a stroke.
(9) Measured humidity value and unit:
Indicates the measured humidity value and unit (%RH (relative humidity) ˚C
(˚ F) (dew point), ˚ C (˚ F) flickering (wet-bulb temperature).
5. Maintenance
(10) [CLEAR] key:
Press this key when resetting the indication setting (hold, humidity unit
selection).
For cleaning it, wipe it off with a dry soft cloth without fail.
Never use benzene, thinner, or the like, otherwise a color change, deformation,
deterioration of sensor, or other troubles may occur.
(11) Unit indication mark:
Storage of temperature-humidity sensor
Indicates the displayed humidity measuring unit.
%RH: relative humidity ˚C (˚F) (DP)lighting: Dew point ˚C (˚ F)(WB) flickering:
Wet-bulb temperature.
For storing the sensor for a long time, seal it into a clean vinyl bag together with
a desiccant like silica gel, and store it at a cool dark palce.
Filter exchange
(12) [SEL] key:
Press this key when changing the measuring unit of humidity.
The general type temperature-humidity sensor (RH31-1) filter can be replaced if
it has become dirty. Remove the cap from the sensor tip by turning it counter-
clockwise, and draw out the filter carefully to as not to damage the sensor.
OPERATION METHOD
Preparation for measurement
Insert new filter with due care so as not to damage the sensor, and screw in the cap.
1. Assembly of battery
Measurement in a very wet atmosphere and moistening
The battery is assembled at the delivery time from the factor and it is employable
as it is. However, the battery life is not guaranteed due to the use for test. If the
battery shortage mark is indicated, replace the battery.
In a very wet atmosphere of higher than 90%RH, dew may be formed due to
a slight drop of the ambient temperature.
Even if dew is formed on the humidity sensor, no characteristic change occurs.
However, it may cause an abnormal measured value. If dew has been formed on
the sensor, dry it at 60 to 70˚ C for about one hour in a thermostatic oven or the
like. Don’t dry it up abruptly. It takes longer than 12 hours to dry up the sensor
at room temperature.
For the method of replacing the battery, refer to [Maintenance].
2. Sensor connection
Connect the sensor securely to the circular connector at the upper part of the
indicator, while taking care of the sensor correction direction.
9
6
Measurement
3. Collection and stop
When the reservation time has been set, the confirmation chime sounds.
After about 3 minutes, the display appears, and the data collection is started
from the reservation time.
Display appears by pressing the [ON-OFF] key after the unit has been ready for
measurement.
The power supply turns off automatically about 3 minutes after the last key
operation has been finished. For canceling the auto off function, press [ON-OFF]
key together with the [CLEAR] key when the power supply is turned off. In this
case, a confirmation chime sounds three times.
After several seconds, the sensor number is displayed as shown in (2).
(Note) The display number may change from 01 to 09 according to the kinds of
sensor, etc. However, it does not affect any measurement at all.
After several seconds, a measured temperature value is indicated in the upper
column, while a measured humidity value is indicated in the lower column as
shown in (3).
The initial value of the humidity unit shows a relative humidity. It changes in the
order of %RH (relative humidity) → ˚ C (˚ F) (dew point) → ˚ C (˚ F)flickering
(wet-bulb temperature) → %RH → ...
(4) shows an example of the dew point indication, while (5) shows an example of
the wet-bulb temperature indication. This display turns to %RH indication when
pressing the [CLEAR] key.
For stopping the data collection, press [ON-OFF] key to display the measured
value, and then, press the [CLEAR] key.
When the data collection start time has already been set, data collection is
executed at the preset time even if the power supply is turned off.
4. Memory
Data can be collected by [temperature, humidity] x 1500.
Data collection is stopped when the memory capacity is fully filled with data.
The measuring interval is fixed to 10 minutes.
If data collection was interrupted halfway, past data are valid, but subsequent
old data become invalid. (Preset 1000 data are valid, but the 500 data collected
last become invalid.)
4 .2 RS2 3 2 Co m m u n ica tio n s
DATA READ
1. Connection to personal computer
Prepare an NEC PC98 series personal computer.
Connect RH31 to the personal computer by using the attached cable.
Attached RS-232C cable
For finishing the measurement, press [ON-OFF] key. The power off function is
set automatically when turning on the power supply next.
KEY OPERATION METHOD WHEN THE UNIT IS
PROVIDED WITH A MEMORY FUNCTION
Personal computer
2. Setting of personal computer
Data Collection
Set RS-232C of the personal computer as follows.
Transfer speed: 1200 bps
Character length: 7 bits Parity: None
Stop bit: 2 bits X parameter: None
1. Present time setting
Display flickers when pressing [WRITE] key.
[Year] flickers when pressing [READ] key and it advances stepwise, each time
[READ] key is pressed once.
3. Data read and stop
When a desired [Year] has been displayed, press the [WRITE] key to define the
year.
For [Month], [Day], [Hour], and [Minute], press [READ] key until they reach a
desired value respectively and press [WRITE] key to define them.
By pressing [CLEAR] key, the setting returns to the last one.
Data are transmitted to the personal computer by pressing the [READ] key.
In this case, data are transmitted in the units of humidity selected by [SEL] key.
Data read is stopped by pressing [CLEAR] key.
Read data (text format) are as shown below
Specify the delimiters of data by comma [,], and use the table calculation soft-
ware (EXCEL, Lotus123, etc. for example). Measured values are described on the
cell numerically.
2. Setting of the data collection start time
Set the data collection start time.
After setting the present time, display flickers.
[Year] flickers when pressing [READ] key and it advances stepwise, each time
[READ] key is pressed once.
When a desired [Year] has been displayed, press the [WRITE] key to define the
year.
For [Month], [Day], [Hour], and [Minute], press [READ] key until they reach a
desired value respectively and press [WRITE] key to define them.
By pressing [CLEAR] key, the setting returns to the last one. Set the reservation
time ahead from the present time without fail.
a. Collection interval b. number
c. Temperature
d. Humidity
e. Measurement start year, month, day, and hour
%RH: Relative humidity C(F): Dew point
$C($F): Wet-bulb temperature
7
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