085A-9800 Relative Humidity Temperature Sensor
Instruction Manual
MODEL 085A
RELATIVE HUMIDITY /
TEMPERATURE SENSOR
MANUAL
085A-9800 Relative Humidity Temperature Sensor
Copyright Notice
Model 085A Relative Humidity / Temperature Sensor Manual.
© Copyright 2022 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: 541-471-7111
Fax: 541-471-7116
E-Mail: service@metone.com
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.
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.
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 8inch 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.
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.
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
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).
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 |
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.
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)
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 |
| 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 | 12368 | 117 | 9215 |
| 100 | 12174 | 118 | 9059 |
| 101 | 11983 | 119 | 8904 |
| 102 | 11794 | 120 | 8751 |
| 103 | 11607 | 121 | 8600 |
| 104 | 11423 | 122 | 8450 |
| 105 | 11241 |
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
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.
4.8.2. Spare Parts
820216 RH SENSOR ELEMENT (Requires factory calibration)
560014 FILTER, MEMBRANE
720050 O-RING (Two required)
Operational Specifications
| Model Number: | 085A |
| Relative Humidity RH Sensing Element: Range: Accuracy: Response Time: |
Thin film polymer capacitor 0 to 100% RH ± 2.0% from 0 to100% RH 10 sec. with 2 m/s aspiration |
| Temperature: Temperature Sensor: Temperature Operation Range: Temperature Coefficient: Accuracy Output: |
Thermistor -30° C to +50° C (-22° F to 122° F) Compensated internally ±0.15° C (0.27° F) Resistive |
| Analog Output: | 0 to 1 VDC Standard 0 to 5.0 VDC Optional |
| Automate Auto ID: | No |
| General: Input Power Dimensions |
10 to 18 VDC @ < 5 mA Length: 8.5 inches (21.59 cm) Diameter: 0.75 inches (1.91 cm) |
Corporate Sales & Service: 1600 NW Washington Blvd. Grants Pass, OR 97526
Tel 541-471-7111 Fax 541-471-7116
www.metone.com – www.service@metone.com
Documents / Resources
 |
Met One 085A-9800 Relative Humidity Temperature Sensor [pdf] Instruction Manual 085A-9800 Relative Humidity Temperature Sensor, 085A-9800, Relative Humidity Temperature Sensor, Humidity Temperature Sensor, Temperature Sensor, Sensor |
