Vts Rh+t-sens-d-modrtu Compact Floor-mounted Air Handling Units Instruction Manual

VTS RH+T-SENS-D-MODRTU Compact Floor-Mounted Air Handling Units Instruction Manual

Introduction

This document describes functionality of air relative humidity and temperature transducer based on integrated Sensirion SHT31-DIS-B sensor, equipped with RS485 interface using MODBUS RTU protocol and 0-5V / 0-10V analogue output.

NOTES: 

1. Read this document carefully before attempting to start up the device!
   
2. The device must be installed by qualified staff only. 

Functions of the device

• relative humidity measurement
• 0-5V or 0-10V analogue output (hardware selectable range) proportional to relative humidity
• 3 status LEDs
• RS485 serial interface for remote management (setup and reading of measurement values)
  • MODBUS RTU protocol
  • integrated terminating resistor 120Ω
  • communication in HALF DUPLEX mode
  • hardware/software configurable address in the range 1-247
  • hardware configurable communication baud rate: 19200, 9600, 4800, 2400
  • software configurable communication baud rate: 115200, 57600, 38400, 19200, 9600, 4800, 2400

Design Features

The main function of the RH&T transmitter is to measure air relative humidity and
temperature using an integrated Sensirion SHT31-DIS-B sensor. The measurement result, as well as the sensor missing/error status, is processed by the built-in microprocessor and then made available on the RS-485 bus via registers of the MODBUS RTU protocol. Additionally, the measurement result air relative humidity is available as analog signal on the 0-5V / 0-10V voltage output.

Technical data

General parameters of the transducer

Power supply

• DC voltage: DC 20-30 V (nom. DC 24 V)
• AC voltage: AC 20-28 V (nom. AC 24 V)

Current consumption

• typical: TBD
• max: TBD

LED indicators

• Signal connection
• Screw terminals in 5mm pitch
• (wire diameter ≤ 2.5mm)

Housing dimensions

• without sampling mast: 80x82x55mm
• with sampling mast: 80x82x280mm

Parameters of humidity measurement

1. The prerequisite for obtaining the given response times is an air flow > 1m/s; the response time indicated is equal to one time constant corresponding to 63 % of the steady value

Parameters of temperatures measurement 

Response time 1)

1. The prerequisite for obtaining the given response times is an air flow > 1m/s; the response time indicated is equal to one time constant corresponding to 63 % of the steady value

Parameters of analogue output

Parameters of serial interface 

Installation

Safety

• The device must be installed by qualified staff only!
• All connections must be made in accordance with wiring diagrams shown in this document!
• Check all electrical connections prior to commissioning!

Device design

Description of terminals

Notes:

1. The RXTX+ and RXTX- signals must be connected to the A and B lines of the MODBUS bus respectively.
2. The analogue output returns following voltage values:

whereas the concentration value can be calculated basing on the voltage value form using the following formula:

where:
VOLTAGERANGE = 5V or 10V (0-5V or 0-10V set on the configuration DIP-switch 2 – see section 3.4)

Exemplary values are shown in the table below:

Configuration of MODBUS bus, serial port and analogue output

The purpose of the consecutive switches of the left DIP-switch is as follows (default values are in bold)

The device address on the MODBUS bus is set using the right DIP-switch:

Note: the configuration set by the means of DIP-switches is read once after device restart (after switching on the power or pressing the RESET button). For this reason, if the DIP switch settings are changed during operation, then after changing the settings, it is necessary to restart the device by pressing the RESET button or temporarily unplugging the power supply

LED indicators

LED POWER 

LED LINK

LED SENSO

Recommendations for installation

It is recommended that devices on the MODBUS (RS485) are connected in a daisy-chain configuration, whereby 120R terminating resistors should be connected between A and B lines of the bus at both ends of the chain (close to the outer devices). This resistor is builtin in the RH&T-SENS-D-MODBRTU transducer and can be switched on using the no. 1 switch on the configuration DIP-switch (see section 3.4).

Moreover, shielded cables should be used when the device is operated in high interference environments and the shield should be connected to the nearest PE point on the power supply side

MODBUS protocol

Register map 

Command table:

Notes: 

• Reading registers from addresses not listed in this table results in 0x02 exception.
• Specifying an incorrect or out-of-range parameter value results in entering the value 0xEEEE into the command register.
• The device is configured by writing three registers (password / command / parameter) at the same time using the 0x10 function with the corresponding values
  • according to the command table, or by writing single registers (using 0x06 or 0x10 function) with the latter writing of a (valid) password causing the execution of the command.
• During a single password entry (both with function 0x06 and 0x10) in case of a password match, the correctness of information in command and parameter registers is checked and if correct, the command is executed

DEV_ID_REG (addr=11=0x000B) – read only

This register is used to store device ID. Meaning of bits: DEV[4..0] = b11000 – fixed value meaning “air parameter sensors” HV[1..0] – value 0..3 – hardware version OPTIONS[4..0] – values 0..31 – device type

• b01000 – RH&T transducer with SHT31-DIS-B sensor
• T[1..0] – value 0..3 – type
• 0 – duct type
• 1 – room type
• 2, 3 – reserved

RH&T duct sensor in basic hardware version returns the value b1100000010000000=0xC080.

SOFT_VER_REG (addr=12=0x000C) – read only

Software version is represented as a sting of 4 characters: N.ABrev where

N, A, B are digits in the the 0..9 range rev (with values 0..9) is a letter in the range ‘a’…’j’.

Examples: 0x0000 represents software version: 0.00a; 0x4321 → 4.32b ; 0x2345 → 2.34f

Protocol functions

Reading the contents of a group of output registers (0x03)

Command format:

Response format:

Error format:

Writing single 16-bit registers (0x06) Command format: 

Response format:

Error format:

Writing a group of output registers (0x10) Command format:

Response format:

Error format:

Description of errors

Data format

Character / byte format

The following figure shows the format of a byte transmitted in the MODBUS RTU protocol. Each transmitted character has 10 or 11 bits, which are sent in order from the least significant to the most significant.

With even / odd parity check

Without parity check (1 or 2 stop bits):

Order of bytes in 16-bit data fields in a transmission frame

The following figure shows the byte order of the 16-bit data fields. For 16-bit data fields, the correct byte order is that the older byte is transmitted first, then the younger byte (HI→LO – BIG ENDIAN), while for the CRC field the younger byte is transmitted first, then the older byte (LO→ HI – LITTLE ENDIAN).

CRC check sum

WORD CRC16 (const BYTE *nData, WORD wLength) static const WORD wCRCTable[] = { 0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241, 0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440, 0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40, 0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841, 0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40, 0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41, 0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641, 0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040, 0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240, 0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441, 0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41, 0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840, 0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41, 0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40, 0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640, 0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041, 0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240, 0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441, 0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41, 0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840, 0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41, 0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40, 0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640, 0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041, 0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241, 0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440, 0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40, 0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841, 0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40, 0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41, 0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641, 0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040};

VTS reserves the right to implement changes without prior notice.
www.vtsgroup.com Page 15 of 16 ver. 2.0 (11.2021)

References

• VTS Group - Air Handling and Conditioning units, Air Curtains, Heating Units
• VTS Group - Air Handling and Conditioning units, Air Curtains, Heating Units