Met One Instruments 085A User manual
Met One Instruments, Inc
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
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: (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.
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
085A-9800 Rev A Page 6
Figure 2 Model 085A-6 Sensor
085A-9800 Rev A Page 7
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.
085A-9800 Rev A Page 8
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).
085A-9800 Rev A Page 10
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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