IO Thrifty HUTX1-485 User manual

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HUTX1-485
Temperature and Humidity Sensor
Revision V1.0
© Copyright 2023 IOThrifty LLC. All rights reserved. This document may not be copied, photocopied, reproduced, translated,
or reduced to any electronic medium or machine-readable form, in whole or in part, without the prior written consent of
IOThrifty LLC
User Manual

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Product Overview
The HUTX1-485 temperature and humidity sensor with RS-485 communications using Modbus-RTU protocol allows
it to be connected to the Modbus network for temperature and humidity measurement and monitoring.
The HUTX1-485 is designed around the SHT3X, a newly designed and improved capacitive humidity sensor which
provides greatly improved performance over the previous generation of sensors (SHT1x and SHT7x) in high humidity
environments.
Setting the Modbus address of HUTX1-485 is done via DIP switch, which avoids the need to set the address by
computer or PLC. It is simple and convenient to maintain and replace.
The HUTX1-485 has excellent long-term stability, low latency, low power consumption, good resistance to chemical
contaminants and excellent repeatability. It is used for accurate temperature and humidity measurement in HVAC,
communication equipment rooms, warehouse buildings, and automatic control applications.
Features
 Low power consumption
 Fully calibrated
 High precision and good repeatability
 Long-term stability, low drift
 Humidity full range temperature compensation
 Standard Modbus-RTU protocol
Application Uses
Generally used in indoor clean environments, such as：
 HVAC
 Building automation
 Laboratory, hospital, library, museums
 Storage and production facilities in the pharmaceutical, paper, food and electronics industries
Power supply
Supply voltage 5 to 24 Vdc
Current 5mA
RS-485 interface
Transmission distance
The maximum transmission distance is about 1200 meters depending on the use environment, transmission material
and transmission rate
Optional 4800bps / 9600bps / 19200bps
Transmission rate
32 Number of theoretical nodes

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Temperature measurement
Sensing element SHT3X
Working range -40 to 85
℃
Resolution 0.1
℃
Measurement accuracy ±0.2
℃
Humidity measurement
Sensing element SHT3X
Working range 0 to 95%RH
Resolution 0.1%RH
Measurement Accuracy ±2%RH
Hysteresis < ±0.8%RH
Response time About 8s (from 33%RH to 75%RH, in flowing air)
Long-term stability <±0.25%RH/year (under no pollution）
Lead cable
Lead Label Function description
Green B- RS485 interface B-
Yellow A+ RS485interface A+
Black GND
Common ground (connect to the negative end of the power supply when DC
power is supplied)
Red V+ Power supply positive (connect to the positive end of the power supply
when DC
power is supplied)

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RS485 wiring diagram
Wire Note:
When setting up an RS485 network, pay attention to the RS485 grounding to eliminate the common mode voltage.
It is suggested to connect the common ground of each sensor together, and then connect it to the ground wire of
the RS-232/RS-485 transverter.
To connect, you can use the shielding layer of the shielded wire as the ground.
DIP switch and address setting
Note: The above picture is a diagram of the DIP switch. The DIP switch has 8 DIP positions. The corresponding
numbers from 1 to 8 are 128, 64, 32, 16, 8, 4, 2, 1, and these values are added together as the address code. As
shown in the figure above, bits 1, 3, and 4 are in the ON position, so the address code 128+32+16=176, that is, the
address code 176
The above figure is a diagram of the correct steps to open the sensor body to expose the DIP switch.

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Protocol
This document contains only the information relevant for the HUTX1-485 regarding the Modbus protocol. There are
many other sources available on the internet which provide more detailed information about Modbus RTU protocol.
Data frame format
Note: The above is the default format of the sensor. If you need a different format, it may be available as a custom
order. Please contact IOthrifty for details.
RTU message frame format
HUTX1-485 follows the Modbus RTU frame protocol. To ensure the integrity of the information, a pause time of 3.5
characters or more is required at the beginning and end of each frame (T1-T2-T3-T4), each byte of the information
frame needs to be transmitted continuously. If there is a pause greater than 1.5 characters, the sensor will treat it as
invalid information and will not respond.
Information frame format
Start address function code Data area CRC check end
T1-T2-T3-T4 1byte 1byte - 5 -N byte 2byte T1-T2-T3-T4
Register Descriptions
Register
Address
Meaning Description Read and write
0 Temperature The unit is 0.1 degree, MSB. First,
complement
format, 7FFF H means error condition.
Read only
1 Relative humidity The unit is 0.1%, MSB First, complement
format, 7FFF H means error condition
Read only
2 Reserved 1 Read only
3 Reserved 2 Read only
4 Address code Set by DIP switch Read only
5 Baud rate Support 4800、9600、19200 Can read and write
6 Hardware version Read only
7 Software version Read only
Address setting
The default setting is 1, user modifiable by dip switch.
Baud rate setting
The default setting is 9600, can be set via software.
Start bit Data bit Parity bit Stop bit
1 8 0 1

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Host request sensor information example (function code 03)
Request data using function code 03 to read the temperature and humidity measurement value of the sensor and
other information. The information frame format of the 03 code is as follows：
Host request information frame Sensor response information frame
Field Description Example
Slave address
01
Function code 03
Return the number of
bytes
10
Temperature data high byte
00
Temperature data low byte FA
Humidity data high byte
02
Low byte of humidity data
58
1 high byte reserved
00
1 low byte reserved 00
2 high byte reserved
00
2 low byte reserved 00
Address code high byte
00
Address code low byte 01
Baud rate high byte 25
Baud rate low byte
80
Hardware version high byte
06
Hardware version low byte 00
Software version high byte 00
Software version low byte 0A
CRC check code low byte D4
CRC check code high byte 64
Field Description
Example
Slave address 01
Function code
03
Register address high byte
00
Register address low byte 00
High byte of query
quantity
00
Low byte of query quantity
08

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Data explanation
Temperature = 00FAH = 250 / 10 = 25.0℃； Humidity = 0258H = 600 / 10 = 60.0%RH； Reserved 1 = 0000H;
Reserved 2 = 0000H; Address code = 0001H = 1; Baud rate = 2580H = 9600; Hardware version = 0600H;
Software version = 000AH = 10 = V1.0;
Note! If users only want to read the temperature and humidity or other registers, they only need to read the
corresponding registers.
Host setting sensor information example (function code 06)
Setting the sensor baud rate (register address is 0005H), and the message frame format is as follows:
Host request information frame Sensor response information frame
Error response
When the host sends request information to the sensor, various errors may occur. At this time, the sensor sets the
highest position of the function code to 1, and then returns an error code. The host can determine whether an error
has occurred by detecting whether the highest bit of the function code is 1.
Return format
Slave address Function code error code CRC check
1 byte 1 byte 1 byte 2 byte
Error code
01：Illegal function code
02：Illegal data address
03 : Illegal data value
Field description Example
Slave address
01
Function code
06
Register address high byte 00
Register address low byte
05
Set value high byte 25
Set value low byte
80
Field description Example
Slave address
01
Function code
06
Register address high byte 00
Register address low byte
05
Set value high byte 25
Set value low byte
80

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CRC check code
Modbus RTU mode uses CRC-16 check, the check code occupies 2 bytes. If the check code is wrong, the sensor will
ignore the host's request and not respond.
The calculation method of CRC-16 check code is as follows:
① Preset a 16-bit register as hexadecimal FFFF, call this register CRC register;
② XOR the first 8-bit binary data (the first byte of the information frame) with the lower 8 bits of the 16-bit CRC
register, and place the result in the CRC register;
③ Shift the content of the CRC register one bit to the right (toward the low bit) and fill the highest bit with 0, check
the right shift out position after shift;
④ If the shifted out bit is 0, repeat step ③ (shift one bit to the right again), if the shifted out bit is 1, the CRC register
is XORed with the polynomial A001 (1010 0000 0000 0001);
⑤ Repeat steps ③ and ④ until the right shift is 8 times, so that the entire 8-bit data has been processed;
⑥ Repeat steps ② to step ⑤ to process the next byte of the message frame;
⑦ After calculating all the bytes of the information frame according to the above steps, the content of the CRC
register obtained is: 16-bit CRC check code.
Dimensions (unit: mm)

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Warranty Terms
IOThrifty LLC ("IOThrifty") warrants that for a period of one year following delivery, the IOThrifty products you have
purchased will (a) perform in accordance with published specifications, and (b) will be free from defects in materials
or workmanship. In the event an IOThrifty Product does not meet this warranty, subject to the conditions set forth in
these terms and conditions, IOThrifty’s sole obligation will be, at its election, to repair or replace the product in
question or to refund the purchase price.
IOThrifty MAKES NO OTHER WARRANTIES, EXPRESS OR IMPLIED, AND ALL IMPLIED WARRANTIES OF
MERCHANTABILITY, NON-INFRINGEMENT AND FITNESS FOR A PARTICULAR PURPOSE ARE HEREBY
DISCLAIMED. IN NO EVENT WILL IOTHRIFTY BE LIABLE FOR PUNITIVE, SPECIAL OR CONSEQUENTIAL
DAMAGES, OR FOR AN AMOUNT IN EXCESS OF THE PURCHASE PRICE OF THE DEFECTIVE IOTHRIFTY
PRODUCT OR PRODUCTS.
This warranty will not apply to any IOThrifty Products that have been (a) damaged by lightning, water, or power
surges, (b) neglected, altered, abused, or used for a purpose other than the purpose for they were provided, (c)
repaired by you or any other party without IOThrifty's prior written authorization, (d) used in conjunction with a third
party product or products not approved in advance by IOThrifty, or (e) otherwise used in a manner inconsistent with
any instructions provided by IOThrifty.
Customer Service and Technical Support
Contact IOThrifty's Customer Service Department for support, return or repair information. Email:
[e-mail], Telephone: [phone]
Copyright
© Copyright 2023 IOThrifty INC. All rights reserved. This document may not be copied, photocopied, reproduced, translated,
or reduced to any electronic medium or machine-readable form, in whole or in part, without the prior written consent of