Met One Instruments 597A User manual

597A-9800 Manual Rev A
MODEL 597A
Temperature / Relative Humidity /
Barometric Pressure Sensor
Operation Manual
Document No. 597A-9800 Rev A
Met One Instruments, Inc
1600 NW Washington Blvd.
Grants Pass, Oregon 97526
Tel: [phone]
Fax: [phone]

597A-9800 Manual Rev A
Copyright Notice
Model 597A Relative Humidity / Temperature / Barometric Pressure Sensor Manual.
© Copyright 2019 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 to resolve your
problem. If you are still experiencing difficulty, you may contact a Technical Service
representative during normal business hours—7:30 a.m. to 4:00 p.m. Pacific Standard Time,
Monday through Friday.
Voice: [phone]
Fax: [phone]
E-Mail: [email protected]
Mail: Technical Services Department
Met One Instruments, Inc.
1600 NW Washington Boulevard
Grants Pass, OR 97526

597A-9800 Manual Rev A
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.

597A-9800 Manual Rev A
Table of Contents
1. Introduction ........................................................................................................... 1
2. Cautionary Statements ......................................................................................... 1
3. Initial Inspection.................................................................................................... 1
4. Product Overview.................................................................................................. 2
5. Installation............................................................................................................. 3
5.1. Mounting................................................................................................................ 3
5.2. Siting...................................................................................................................... 3
5.3. Wiring..................................................................................................................... 3
6. Specifications* ...................................................................................................... 4
7. Sensor Verification ............................................................................................... 5
8. Serial Communications ........................................................................................ 5
9. Maintenance .......................................................................................................... 7
10. Service ................................................................................................................... 7
11. Wiring Diagrams.................................................................................................... 8
12. Terminal Mode and SDI Commands.................................................................. 10

597A-9800 Manual Rev A Page | 1
1. Introduction
The Model 597A multi-parameter weather sensor is an “All-in-One” device that measures
ambient temperature, relative humidity and barometric pressure. Sensor performance
complies with guidelines establish by the World Meteorological Organization (WMO) and
the US Environmental Protection Agency (EPA). The sensor is supplied with mounting
hardware and an integrated radiation shield and can be easily attached to lattice tower legs
and instruments masts up to 2 inches (IPS) in diameter. The Model 597A is supplied with
output terminals that digital output signals in several formats.
2. Cautionary Statements
•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.
•To minimize exposure to direct sunlight install the sensor facing to the north in the
northern hemisphere and south in the southern hemisphere. This orientation will help
shield the sensor from direct sunlight and reduce temperature measurement errors.
3. Initial Inspection
•Upon receipt of the Model 597A, inspect the packaging and contents for damage. If the
packaging has arrived in a damaged condition file a claim with the shipping company
and contact Met One Instruments, Inc. to arrange for repair or replacement.
•The model number and cable length are printed on a label at the connection end of the
cable. Check this information against the shipping documents to ensure the correct
product and cable length has been received.

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4. Product Overview
The 597A ships from Met One Instruments pre-wired for digital output signals including RS--
232, RS-485 and SDI-12. The 597A also includes voltage outputs for AT/RH/BP, and an ID
voltage used by some Met One monitors and dataloggers to identify the sensor. The voltage
outputs are 0-2.5VDC default, and can be changed to 0-1VDC or 0-5VDC.
The 597A uses a piezoresistive pressure sensor, a microprocessor-controlled relative humidity
module, and a platinum RTD temperature sensing element. The response of each element is
linear with negligible hysteresis. Each sensor element in the 597A is controlled using an on-
board microcontroller, which contains an analog-to-digital converter and non-volatile memory
for storage of factory-determined calibration coefficients. The microcontroller polls the sensor
module once per second. Measurements are temperature corrected, the calibration
coefficients applied, and the processed measurement sent out via serial communication.
All wiring terminals on the 597A are protected from static-surge damage by transzorbs and
current-limiting resistors.

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5. Installation
5.1. Mounting
The 597A is designed for outdoor use and is supplied with an integrated solar radiation
shield and U-bolts. Install the radiation shield with the U-bolts on any vertical or
horizontal pipe up to 2 inches (IPS) in diameter. To minimize exposure to direct sunlight
install the sensor facing north in the northern hemisphere and south in the southern
hemisphere.
5.2. Siting
Install the sensor over an open, level area at least 9 m (EPA) in diameter. The surface
should be covered with short grass or a natural earth surface where grass does not
grow. Locate sensors away from objects at a distance equal to four times the height of
the objects, and at least 30 m (EPA) from large paved areas. Protect sensors from
thermal radiation and ensure adequate ventilation.
Standard installation heights:
•1.5 m (AASC)
•1.25 to 2.0 m (WMO)
•2.0 m (EPA)
5.3. Wiring
The 597A is ordered with a 10547 analog output cable assembly, or 10548 digital output cable
assembly (sold separately). Individual wire leads connect the 597A to a data logger, signal
conditioner, or programmable logic controller. A detailed wiring diagram for each cable
assembly is provided in Section 10: Wiring Diagrams.

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6. Specifications*
TEMPERATURE
•Range: -50 °C to +70 °C (-58 °F to +158 °F)
•Accuracy(1): Digital: ±0.2 °C
Analog: ±0.2 °C, +/-1 mV
•Resolution: 0.01 °C
RELATIVE HUMIDITY
•Range: 0 to 100 %
•Accuracy(1): Digital: ±2 %
Analog: ±2 %, +/-1 mV
•Resolution: 0.1 %
PRESSURE
•Range: 500 to 1100 mbar (14.8 inHg to 32.5 inHg)
•Accuracy(1): Digital: ±0.5 mbar
Analog: ±0.5 mbar, +/-1 mV
•Resolution: 0.01 mbar
ELECTRICAL
•Measurement Rate: 1 Hz
•Data Storage: None
•Standard Signal Output: RS-232C, SDI-12 , RS-485, 0-2.5 VDC
•Optional Signal Output: 0-1 VDC, 0-5 VDC
•Power Supply: 9-36 VDC, 25 mA typical @ 12 VDC
ENVIRONMENTAL
•Temperature: -50 °C to +70 °C
•Humidity: 0 to 100 %
PHYSICAL
•Diameter: 7 in (178 mm)
•Length: 8 in (203 mm)
•Weight: 5 lb (2.3 kg)
(1) At 25°C

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7. Sensor Verification
To verify correct wiring and test the basic sensor operation, blow on the sensor. The
warmth and moisture in your breath should cause the temperature and relative humidity
reading to rise. The output signals can also be checked against calibrated relative humidity,
temperature and pressure devices. Please note that relative humidity can be expected to
vary significantly over short distances and in brief periods of time.
8. Serial Communications
Serial Data Output
The output of the 597A is a fixed length, comma delimited, serial data stream. The serial
output is factory set for 9600 baud, no parity, 8 data bits, with 1 stop bit (N, 8, 1). Please
see appendix E for a list of supported serial commands.
Output Format Detail
The 597A will support only one output format. This format will use fixed length fields but
also include commas to accommodate both standard CSV formatting and legacy
programs that expect fixed length fields.
The parameter order is shown in the table below.
Field Parameter
01 Ambient Temperature
02 Relative Humidity
03 Barometric Pressure
04 Config. & Status
05 Check Sum
The 597A will report data at a rate set using the “OI” user command (see Section 12 for
command details), and is typically set to one second. An example output string is
shown below.
+023.61,022.1,0974.31,U0,*nnnn

597A-9800 Manual Rev A Page | 6
Note: when displaying the pressure in In/Hg, there will be an extra leading zero
character but the fixed length of the field will not change.
A check sum parameter will be added to the end of the message (*nnnn). The check
sum is the addition of all the characters from the start of the message through the first
character preceding the asterisk (*). The check sum is expressed as a decimal number.
This is a 16-bit sum and should not overflow past 4 digits, given the number of
characters in the output string.
Polled Data Mode (RS232 or RS485)
The sensor can be set for polled data mode instead of continuous serial output, by
setting the serial trigger string while in terminal mode (see Section 12 for command
details).
SDI-12 Interface
In addition to the above communications methods, the sensor can be polled for data by
an SDI-12 Master Station. This operates completely independent of the RS232 or
RS485 communications and can be used in conjunction with those methods. Data are
polled using a series of SDI-12 commands. Please see appendix E for a list of
supported SDI commands. The default SDI Address for the 597A is zero.
Please consult your data-logger manual for more information on SDI interfaces or call
Met One for additional help.

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9. Maintenance
General Maintenance Schedule
6 – 12 Month Intervals:
Inspect the sensor for proper operation per Section 7.
12 - 24 Month Interval:
Return the sensor to Met One Instruments, Inc. for factory inspection and calibration.
10. Service
The 597A is not field repairable and should be returned to the factory for service.
Detailed calibration & service information and pricing are available from the Met One
Instruments, Inc. Service department at [email protected] and 541-471-7111.

Page 8 597A-9800 Manual Rev A
11. Wiring Diagrams
PIN NO WIRE COLOR WIRE LABEL DESCRIPTION
1 Red +12VDC +9 to +36 VDC
2 Black Gnd Signal Ground
3 Orange Ana Gnd Analog Ground
4 Brown RH RH Analog Output
5 Green ID ID Voltage
6 White BP BP Analog Output
7 Blue AT AT Analog Output
Wiring Instructions (PN 10547; Analog Output)

597A-9800 Manual Rev A Page | 9
Wiring Instructions (PN 10548; Digital Output)
PIN NO WIRE COLOR WIRE LABEL DESCRIPTION
1 Black PWR GND Power Ground
2 Red + Vin +9 to +36 VDC
3 Blue SDI-12 SDI-12 Output
4 Green SIG GND Signal Ground
5 White RS-232 Tx RS-232 Transmit
6 Brown RS-232 Rx RS-232 Receive
7 Orange RS-485 - RS-485 signal -
8 Yellow RS-485 + RS-485 signal +
White/Brown Shield Earth Ground

Page 10 597A-9800 Manual Rev A
12. Terminal Mode and SDI Commands
RS232 / RS485 Terminal Mode Commands
Terminal mode is activated by entering three carriage return characters within a 2
second period.
Note: Terminal mode times-out after 2 minutes of inactivity.
Successful entry into Terminal Mode will return an asterisk prompt. Typing H,h, or ? will
return a help menu:
H,h,? - Display Help Menu
H,h,? - This Help Menu
DR - Display Range Switch Setting for Analog Output
ID – View / Set Instrument ID
LC - Display Last Calibration information
OI - Set Output Interval
PU - Set Pressure Units
TU - Set Temperature Units
SA - SDI Address
ST - Set Serial Trigger Address
RV - Display Firmware Version Number
QH - Display Record Header
Q - Quit command mode and save any changes
NOTE: The commands noted in this appendix will change both the RS232 and RS485
outputs.
See the section below for SDI-12 commands.

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DR – Display Range Switch Setting
Display the range switch settings for PB and analog output voltage
COMMAND RESULT
DR<cr> 500 to 1100 mbar (Range 16 ) = 0 – 2.5 Volt on Analog Output
ID – Read or Set the Instrument ID
Read or Set the instrument ID
COMMAND RESULT
ID<cr> Instrument ID = nn (where n = id number from 1 to 99)
IDnn<cr> Instrument ID is set to nn
(where nn = 1 to 99, Default = 1)
LC – Read the last calibration information.
Read the serial number, last calibration date, and correction factor
COMMAND RESULT
LC<cr> Annnnn-nnnnn 10/15/12 0.00 (where n = serial number)
OI - Output Interval
Read or Set the Output Interval for this serial port
Note: This command is not supported by SDI-12.
COMMAND RESULT
OI<cr> Report Output Interval setting
OI<cr> Sensor Output every 1 second (Default)
OI2<cr> Sensor Output every 2 seconds
OI3<cr> Sensor Output every 5 seconds
OI4<cr> Sensor Output every 15 seconds
OI5<cr> Sensor Output every 30 seconds
OI6<cr> Sensor Output every 60 seconds

Page 12 597A-9800 Manual Rev A
PU - Pressure Units
Read or Set this serial port’s output units for Pressure
COMMAND RESULT
PU<cr> Report Units setting
PU0<cr> Millibars (mbar Default)
PU1<cr> Inches of Mercury (inHg)
PU2<cr> Millimeters of Mercury (mmhg)
TU - Temperature Units
Read or Set this serial port’s output units for Temperature
COMMAND RESULT
TU<cr> Report Units setting
TU0<cr> Celsius (Default)
TU1<cr> Fahrenheit
SA – SDI12 Address
Read or Set the SDI12 Address
COMMAND RESULT
SA<cr> SA = 0 (Default = 0)
SAn<cr> SDI12 address is set to ‘n’ where 'n'
is in the range [0-9] [A-Z] or [a-z]
Case Sensitive

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ST - Serial Trigger
Read or Set the Serial Trigger character string (Poll command)
COMMAND RESULT
ST<cr> Report Serial Trigger string setting (serial output provides help)
ST XXXXXX<cr> Set Serial Trigger (Default = 1)
RV - Software Version Number
Report the current firmware version number
COMMAND RESULT
RV<cr> Current firmware version
QH – Display Record Header
Report the format of the record output for the current engineering unit settings.
COMMAND RESULT
QH<cr> AT(C),RH(%),BP(mbar),ST (ST = 597A status)

Page 14 597A-9800 Manual Rev A
SDI-12 Commands
NAME SDI-12
COMMAND SENSOR RESPONSE
Address Query ?! a<CR><LF>
Where a = address
Acknowledge Active a!a<CR><LF>
Where a = address
Send Identification aI! a13METONE 597A 0.1
0Axxxxx<CR><LF>
Where a=address and xxxxx = S/N
Change Address aAb!b<CR><LF>
Where b = new address
Start Measurement aMC! a0003<CR><LF>
Where a = address
Send Data aD0! a+bbb.bb+ccc.c+ddd.dd<CR><LF>
Where a = address, bbb.bb = temperature,
ccc.c = relative humidity and
Send Data dddd.dd = barometric pressure
Start Concurrent
Measurement aC! a00003<CR><LF> Where a = address
Start Concurrent
Measurement with CRC aCC! a00003<CR><LF> Where a = address
Continuous Measurements aR0! a+bbb.bb+ccc.c+ddd.dd<CR><LF>
Where a = address, bbb.bb = temperature,
ccc.c = relative humidity and
Send Data dddd.dd = barometric pressure
Continuous Measurements
with CRC aRC0! a+bbb.b+ccc.c+ddd.d<CR><LF>
Where a = address, bbb.b = temperature,
ccc.c = relative humidity and
Send Data dddd.d = barometric pressure,
and {crc} = CRC
Report Temperature Units aXTU! aXTUd<CR><LF>
Where a = address, and
d = 0 for Celsius (default), or
1 for Fahrenheit
Set Temperature Units aXTUd!

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NAME SDI-12
COMMAND SENSOR RESPONSE
Report Pressure Units aXPU! aXPUf<CR><LF>
Where a = address, and
f = 0 for Millibars (default), or
1 for Inches of Mercury
Set Pressure Units aXPUf!
Report Version Number aXRV! aXVNxx.x<CR><LF>
Where a = address and
xx.x = firmware version