Met One Instruments 085A User manual

Met One Instruments, Inc
Corporate Sales & Service: 1600 NW Washington Blvd. Grants Pass, OR 97526
Tel [phone] Fax [phone]
www.metone.com - [e-mail]
MODEL 085A
RELATIVE HUMIDITY /
TEMPERATURE SENSOR
MANUAL

085A-9800 Rev A Page 2

085A-9800 Rev A Page 3
Copyright Notice
Model 085A Relative Humidity / Temperature Sensor Manual.
© Copyright 2021 Met One Instruments, Inc. All Rights Reserved Worldwide. No part of
this publication may be reproduced, transmitted, transcribed, stored in a retrieval
system, or translated into any other language in any form by any means without the
express written permission of Met One Instruments, Inc.
Technical Support
Should you require support, please consult your printed documentation or our website
www.metone.com to resolve your problem. If you are still experiencing difficulty, you
may contact a Technical Service representative during normal business hours;
Monday – Friday 7:00 a.m. to 4:00 p.m. Pacific Time.
Voice: [phone]
Fax: [phone]
E-Mail: [e-mail]
Mail: Technical Services Department
Met One Instruments, Inc.
1600 NW Washington Blvd
Grants Pass, OR 97526
Safety Notice
The contents of this manual have been checked against the hardware and software
described herein. Since deviations cannot be prevented entirely, we cannot guarantee
full agreement. However, the data in this manual is reviewed regularly and any
necessary corrections included in subsequent editions.
Faultless and safe operation of the product presupposes proper transportation, storage,
and installation as well as careful operation and maintenance. The seller of this
equipment cannot foresee all possible modes of operation in which the user may
attempt to utilize this instrumentation. The user assumes all liability associated with the
use of this instrumentation. The seller further disclaims any responsibility for
consequential damages.

085A-9800 Rev A Page 4
Table of Contents
1. GENERAL INFORMATION .................................................................................... 5
1.1. Description ........................................................................................................................... 5
1.2. 085A Options ........................................................................................................................ 7
1.2.1. Radiation Shield Compatibility Option: ............................................................................ 7
2. SENSOR SITING .................................................................................................... 7
3. INSTALLATION ...................................................................................................... 8
3.1. Mounting Instructions ............................................................................................................ 8
3.2. Wiring Instructions ................................................................................................................ 9
4. OPERATIONAL CHECK-OUT AND CALIBRATION ........................................... 10
4.1. Relative Humidity Sensor Check-out ................................................................................... 10
4.2. Limitations of RH Measurements at Below Freezing Temperatures ..................................... 10
4.3. Temperature Sensor ........................................................................................................... 11
4.4. Temperature Table ............................................................................................................. 12
4.4.1. Temperature to Resistance Table (Celcius) .................................................................. 12
4.4.2. Temperature to Resistance Table (Fahrenheit) ............................................................. 13
4.5. Temperature Sensor Data Logger Connection .................................................................... 15
4.6. General Maintenance Schedule .......................................................................................... 16
4.7. 085A Relative Humidity Sensor Maintenance and Calibration .............................................. 16
4.8. Sensor Maintenance ........................................................................................................... 16
4.8.1. Sensor Element ............................................................................................................ 16
4.8.2. Spare Parts .................................................................................................................. 17
5. Operational Specifications ................................................................................. 18

085A-9800 Rev A Page 5
1. GENERAL INFORMATION
1.1. Description
The 085A sensor is an extremely accurate microprocessor controlled relative humidity
and temperature sensor. The relative humidity sensor responds to the full range of 0 to
100% humidity. Response is linear with negligible hysteresis or temperature
dependence. The temperature sensor is a two-element composite thermistor type with
linear response over the range of –30°C to +50°C. The sensor is designed to be
mounted in a radiation shield when used outdoors. The exact model number you order
will determine the functions of your sensor. The following section describes the model
number feature assignments.
Figure 1 Model 085A-35 Sensor

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Figure 2 Model 085A-6 Sensor

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1.2. 085A Options
The 085A options are defined by dash numbers as follows:
085A-__ (Shield Option)
1.2.1. Radiation Shield Compatibility Option:
6 = Use with Model 076B motor aspirated radiation shield. This sensor comes with 8-
inch long pigtail wires for connection to the radiation shield junction box. Refer to the
radiation shield manual for sensor and cable connections.
35 = Use with Model 074 naturally aspirated radiation shield. This sensor has a circular
connector for use with Met One Instruments cable PN 2348.
2. SENSOR SITING
The EPA recommends sensor mounting in a radiation shield at a 2 meter height, ideally
over green mowed grass to minimize related terrestrial radiation errors on the
temperature and relative humidity readings. Typical installations may vary significantly
from these recommendations due to geographic limitations or specific monitoring
requirements.

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3. INSTALLATION
If the sensor is to be mounted in a radiation shield, refer to Figure 2 and\or the radiation
shield manual section for mounting details. Typical installations are shown below.
Sensors not installed in a radiation shield should be mounted in a representative
location having good airflow and shaded from sunlight or other heat radiation sources
that would affect measurement of relative humidity or temperature.
3.1. Mounting Instructions
Figure 2 Radiation Shield Installation
SENSOR WIRE
CONNECTIONS IN
J-BOX:
TERMINAL WIRE
7 GRN
8 YEL/ORG
9 WHT
REMOVE CLIPS FROM
INNER TUBE USING
LONG NEEDLE NOSE
PLIERS. PLACE
SENSOR IN CLIPS AND
REINSTALL. PUSH
SENSOR INTO INNER
TUBE AS DEEP AS
POSSIBLE WITHOUT
TOUCHING BOTTOM
PLATE
INSTALL SENSOR INTO
TRIANGULAR MOUNTING
ADAPTER AND ATTACH
ADAPTER PLATE TO
SHIELD
SLIDE SENSOR INTO
THE SHIELD UNTIL THE
TOP TOUCHES THE
PLATE. BACK OUT
ABOUT ½” AND SECURE
THE SENSOR TO THE
MOUNTING ADAPTER
BY TIGHTENING THE
TWO SET SCREWS
WITH SUPPLIED 5/64”
ALLEN WRENCH.

085A-9800 Rev A Page 9
3.2. Wiring Instructions
Sensor Connection Wire Color Description
Pin A White +10 to +18 VDC
Pin B Green Signal Ground
Pin C Yellow or Orange RH Analog Output
Pin D Black Temperature Common
Pin E Red Temperature Signal
Pin F No Connection No Connection
No Connection White/Brown Shield
Figure 3 Electrical Connector
View looking at connector pins. (Pins are also identified on connector).

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4. OPERATIONAL CHECK-OUT AND CALIBRATION
4.1. Relative Humidity Sensor Check-out
To verify correct wiring and test the basic sensor operation, blow on the sensor. The
moisture in your breath should cause the relative humidity reading to rise.
The relative humidity sensor has been calibrated at the factory. To check for proper
operation of the sensor it is advised that the output signal be checked against a local
weather service facility or a local relative humidity measuring device such as a
psychrometer. Due to normal atmospheric and geographical variations, the local
weather service data should be used only as a guideline. Ambient air relative humidity
can be expected to vary significantly over short distances and in brief periods of time.
4.2. Limitations of RH Measurements at Below Freezing Temperatures
The sensor’s relative humidity output is referenced to saturated water vapor pressure
above liquid water. When the air temperature is below freezing, the sensor’s maximum
theoretical measurement range is limited as follows:
Air Temperature
(Deg C)
Maximum RH
(%)
0 100
-5 96
-10 92
-15 88
-20 84
-25 80
-30 76
-35 72
-40 68
-45 64
-50 60

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4.3. Temperature Sensor
Compare readings with a precision NIST-traceable temperature sensor. Calibration
verification should be performed using a Met One Instruments Model 5472 Thermal
Mass to assure that both instruments are at the same temperature. This is an
aluminum mass with drilled recesses for the 085A sensor and a standard temperature
sensor (NIST thermometer or RTD). The mass can be used in air or can be partially
submerged in ice or an ice bath. The 085A sensor should not be submerged.
Figure 4 - 5472 Thermal Mass
5472 Thermal Mass
085A Sensor Reference Standard

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4.4. Temperature Table
4.4.1. Temperature to Resistance Table (Celsius)
Model 085A-X Temperature vs. Sensor Resistance
TEMP DEG C RCAL TEMP DEG C RCAL
-30 110236 10 26155
-29 104464 11 25436
-28 99187 12 24739
-27 94344 13 24064
-26 89882 14 23409
-25 85760 15 22775
-24 81939 16 22159
-23 78388 17 21561
-22 75079 18 20980
-21 71988 19 20416
-20 69094 20 19868
-19 66379 21 19335
-18 63827 22 18816
-17 61424 23 18311
-16 59157 24 17820
-15 57014 25 17342
-14 54986 26 16876
-13 53064 27 16421
-12 51240 28 15979
-11 49506 29 15547
-10 47856 30 15126
-9 46284 31 14715
-8 44785 32 14314
-7 43353 33 13923
-6 41985 34 13541
-5 40675 35 13167
-4 39421 36 12802
-3 38218 37 12446
-2 37065 38 12097
-1 35957 39 11756
0 34892 40 11423
1 33868 41 11097
2 32883 42 10777
3 31934 43 10465
4 31019 44 10159
5 30136 45 9859
6 29284 46 9566
7 28462 47 9279
8 27667 48 8997
9 26899 50 8450
*VALUE WITH 18.7K RESISTOR IN PARALLEL WITH SENSOR
RANGE -30C TO +50C
THERMISTOR BEAD 44203
Tc= -(R*18700/(18700+R)-12175)/127.096
Rt = -(127.096*Tc-12175)*18700/(127.096*Tc-12175+18700)

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4.4.2. Temperature to Resistance Table (Fahrenheit)
Model 085A-X Temperature vs. Sensor Resistance
TEMP DEG F RCAL TEMP DEG F RCAL
-22 110236 33 34319
-21 106964 34 33757
-20 103855 35 33207
-19 100895 36 32669
-18 98075 37 32141
-17 95385 38 31625
-16 92816 39 31119
-15 90361 40 30622
-14 88011 41 30136
-13 85760 42 29659
-12 83602 43 29192
-11 81532 44 28733
-10 79543 45 28283
-9 77632 46 27841
-8 75794 47 27408
-7 74025 48 26983
-6 72321 49 26565
-5 70678 50 26155
-4 69094 51 25753
-3 67565 52 25357
-2 66088 53 24969
-1 64661 54 24587
0 63281 55 24212
1 61946 56 23843
2 60654 57 23481
3 59402 58 23125
4 58190 59 22775
5 57014 60 22430
6 55874 61 22091
7 54768 62 21758
8 53694 63 21430
9 52651 64 21108
10 51637 65 20790
11 50652 66 20478
12 49695 67 20170
13 48763 68 19868
14 47856 69 19570
15 46974 70 19276
16 46114 71 18987
17 45277 72 18703
18 44461 73 18422
19 43666 74 18146
20 42890 75 17874
21 42134 76 17606
22 41395 77 17342
23 40675 78 17081
24 39972 79 16825
25 39285 80 16572
26 38614 81 16322
27 37958 82 16076
28 37317 83 15834
29 36691 84 15595
30 36078 85 15359
31 35479 86 15126
32 34892 87 14897

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Model 085A-X Temperature vs. Sensor Resistance
TEMP DEG F RCAL TEMP DEG F RCAL
88 14670 106 11061
89 14447 107 10883
90 14227 108 10707
91 14009 109 10534
92 13794 110 10362
93 13583 111 10193
94 13374 112 10025
95 13167 113 9859
96 12963 114 9696
97 12762 115 9534
98 12564 116 9374
99 21368 117 9215
100 12174 118 9059
101 11983 119 8904
102 11794 120 8751
103 11607 121 8600
104 11423 122 8450
105 11241
*VALUE WITH 18.7K RESISTOR IN PARALLEL WITH SENSOR
RANGE -22˚F TO +122˚F
THERMISTOR BEAD 44203
Tc= -(R*18700/(18700+R)-12175)/127.096
Rt = -(127.096*Tc-12175)*18700/(127.096*Tc-12175+18700)

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4.5. Temperature Sensor Data Logger Connection
The voltage across the sensor has a linear correlation to temperature when a precision
18700 0.1% resistor (Met One Instruments part number 80685) is connected in
series with the excitation voltage. This resistor is built into Met One Instruments data
loggers configured for this sensor and supplied with the 085A sensor for use with other
equipment. Contact Met One Instruments to obtain a replacement resistor. Maximum
recommended excitation is 3.2V. Higher excitation voltage will cause self-heating of the
thermistors, and result in temperature measurement errors.
Reference Voltage -30.0 °C +50.0 °C
1.000 0.855 VDC 0.311 VDC
2.000 1.710 VDC 0.622 VDC
2.500 2.137 VDC 0.778 VDC
5.000 (DO NOT USE)
Signal Voltage vs. Temperature for Various Excitation Voltages
Data Logger Connection
R1
23100 0.1%
YELLOW or ORANGE RH OUTPUT
TO DATA LOGGER SIGNAL INPUT
083E CONNECTOR
F
E
D
C
A
B
BLACK TEMPERATURE COMMON (CONNECT TO SIGNAL GROUND)
REFERENCE VOLTAGE
RED TEMPERATURE SIGNAL OUTPUT (CONNECT TO SUPPLIED NETWORK RESISTOR)
GREEN GROUND
WHITE + 10 TO 18 VDC
R1
18700 0.1%
085A CONNECTOR

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MAINTENANCE AND TROUBLE SHOOTING
4.6. General Maintenance Schedule
6 – 12 Month Intervals:
 Inspect the sensor for proper operation per Section 4.0.
12 Month Interval:
 Return the sensor to Met One Instruments for calibration.
 Replace the two 720050 O-Rings.
 Replace the 860014 Filter Membrane.
4.7. 085A Relative Humidity Sensor Maintenance and Calibration
WARNING: The sensor can be incorrectly calibrated or permanently damaged through
improper acts. Do not attempt a repair or calibration if you are unsure of the procedure.
Do not touch the sensor element if you do not know the correct procedure.
The instrument should operate for an extended period of time with a minimum of care or
maintenance.
The sensor should be re-calibrated every 12 months.
If parts or maintenance assistance are required, contact Met One Instruments. Obtain
shipping instructions and a return authorization (RA) before returning any unit.
4.8. Sensor Maintenance
4.8.1. Sensor Element
The RH sensor element is not user-replaceable (replacement requires sensor
recalibration). If the element becomes damaged, please send the 085A sensor to Met
One Instruments for repair. Please obtain shipping instructions and a return
authorization (RA) number before returning any unit.
Met One Instruments manufactures an RH Calibration Kit part number 10233 which can
be purchased to perform a calibration after the sensor element is replaced. Please
contact the Met One Service Department to purchase the calibration kit.

085A-9800 Rev A Page 17
4.8.2. Spare Parts
Figure 5 Spare Parts
820216 RH SENSOR ELEMENT (Requires factory calibration)
560014 FILTER, MEMBRANE
720050 O-RING (Two required)
560014
Thermistor
820216
720050

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5. Operational Specifications
Model Number: 085A
Relative Humidity
RH Sensing Element: Thin film polymer capacitor
Range: 0 to 100% RH
Accuracy: ± 2.0% from 0 to100% RH
Response Time: 10 sec. with 2 m/s aspiration
Temperature:
Temperature Sensor: Thermistor
Temperature Operation Range: -30° C to +50° C (-22° F to 122° F)
Temperature Coefficient: Compensated internally
Accuracy ±0.15° C (0.27° F)
Output: Resistive
Analog Output: 0 to 1 VDC Standard
0 to 5.0 VDC Optional
AutoMet Auto ID: No
General:
Input Power 10 to 18 VDC @ < 5 mA
Dimensions Length: 8.5 inches (21.59 cm)
Diameter: 0.75 inches (1.91 cm)