Dual-Channel PT100 Temperature Sensor
User Manual

Model: YTL-PT100-2CH-RS485  |  Supports 2-wire/3-wire  |  MODBUS RTU  |  RS485 Upload

1. Product Overview

This product is a dual-channel PT100 temperature data logger featuring a built-in high-precision ADC conversion circuit. It converts the resistance values of two PT100 sensors into temperature data, aggregates the data, and transmits it via RS485 bus using the MODBUS RTU protocol. Suitable for industrial multi-point temperature monitoring, cold chain storage, pipeline temperature measurement, laboratory recording, and similar applications.

Key Features Simultaneous acquisition of 2 PT100 temperature channels; Each channel independently supports 2-wire or 3-wire connection; Temperature data aggregated and uploaded via RS485; Wide voltage supply (5~9V), low power design.

2. Technical Specifications

ParameterSpecification
Supply Voltage5.0 ~ 9 VDC (5V or 9V recommended)
Power Consumptionโ‰ค 0.3W (โ‰ค 60mA @ 5V)
Number of Input Channels2 independent PT100 channels
Sensor TypePT100 Platinum RTD (ฮฑ=0.00385)
Temperature Measurement Range-50โ„ƒ ~ +300โ„ƒ (expandable to -200โ„ƒ~+600โ„ƒ)
Measurement Accuracyยฑ0.3โ„ƒ @ 0~100โ„ƒ, ยฑ0.5โ„ƒ @ full range
Resolution0.1โ„ƒ
Sampling RateApprox. 2 samples/second per channel
Wiring Method2-wire or 3-wire selectable per channel
Communication InterfaceRS485 (half-duplex)
Communication ProtocolMODBUS RTU
Baud Rate9600 (default, configurable 4800/19200/38400)
Data Format8 data bits, no parity, 1 stop bit (8N1)
Device Address1~247 (default 1, configurable)
Operating Temperature-40โ„ƒ ~ +85โ„ƒ
DimensionsApprox. 100ร—50ร—35mm (DIN rail mount optional)

3. Wiring Instructions

3.1 Power and Communication Terminals

Terminal LabelDescriptionWiring Recommendation
VCCPower Positive (5~9V DC)Connect to 5V or 9V power positive
GNDPower NegativeConnect to power negative, also serves as RS485 reference ground
A / 485ARS485 A+ (non-inverting)Connect to host A+
B / 485BRS485 B- (inverting)Connect to host B-

3.2 PT100 Input Terminals (Channel 1 / Channel 2)

ChannelTerminal Label2-Wire Connection3-Wire Connection
CH1IN1+Connect to one end of PT100Connect to one end of PT100 (A)
IN1-Connect to other end of PT100Connect to other end of PT100 (B, common ground)
REF1Not connectedConnect to PT100 compensation wire (C, same potential as B)
CH2IN2+Same rules as CH1
IN2-Same rules as CH1
REF2Same rules as CH1
Note: 2-wire connection is simple but wire resistance introduces error (approx. 0.4โ„ƒ/ฮฉ), suitable for short distances (<5m). 3-wire connection automatically cancels wire resistance, recommended for long distances (>5m) or high-precision applications. Different wiring methods can be mixed between channels.

4. MODBUS Communication Protocol

4.1 Register List (Function Code 03 / 04)

Register Address (HEX)ParameterData TypeDescription
0x0000Channel 1 Temperature16-bit signed integerUnit: 0.1โ„ƒ, actual value = register value รท 10
Example: 0x012E=302 โ†’ 30.2โ„ƒ
0x0001Channel 2 Temperature16-bit signed integerUnit: 0.1โ„ƒ, same as above
0x0100Device Address16-bit1~247, default 1, supports function code 06
0x0101Baud Rate16-bit0:9600, 1:4800, 2:19200, 3:38400, default 0
0x0102Temperature Unit16-bit0:Celsius (default), 1:Fahrenheit
Power cycle required after modifying address/baud rate (power off and on).

4.2 Read Two-Channel Temperature Example

Host Request (Address 1, read 2 registers):
01 04 00 00 00 02 71 CB
Slave Response (Channel 1=25.6โ„ƒ, Channel 2=98.5โ„ƒ):
01 04 04 01 00 03 D9 72 9B
Parsing: Channel 1: 0x0100=256 โ†’ 25.6โ„ƒ; Channel 2: 0x03D9=985 โ†’ 98.5โ„ƒ

4.3 Modify Device Address Example

Change address 1 to address 2 (function code 06, register 0x0100):
01 06 01 00 00 02 89 F6

4.4 Change Baud Rate to 19200

01 06 01 01 00 02 99 F6 (Host baud rate must be changed to 19200 after modification)

5. Usage Steps

  1. Install PT100 Probe: Secure the PT100 sensor at the measurement point.
  2. Wiring: Connect PT100 (note 2-wire/3-wire connection), power supply (5~9V DC), and RS485 A/B lines.
  3. Power On: The indicator light (if available) will flash once, device starts.
  4. Communication Test: Use a MODBUS master to send read commands (function code 03/04).
  5. Data Parsing: Calculate actual temperature with 0.1โ„ƒ resolution.
  6. Multi-device Networking: Assign a unique address to each device and connect in parallel on the RS485 bus.

6. Data Aggregation and Upload

The device internally completes the following process: Collect PT100 resistance values from Channel 1 and Channel 2 โ†’ ADC conversion and compensation โ†’ Convert to temperature values (0.1โ„ƒ) โ†’ Store in internal registers โ†’ Wait for host to read via RS485 using MODBUS protocol. Temperature data from both channels are stored simultaneously. The host can obtain all temperature data with a single read command (reading 2 registers).

7. Important Notes

โš ๏ธ Power Supply Limitation: Supply voltage must not exceed 9V DC, otherwise circuit damage may occur.
โš ๏ธ PT100 Type: Only supports PT100 with ฮฑ=0.00385 (European standard), does not support PT1000.
โš ๏ธ Wiring Length: 2-wire โ‰ค 5m, 3-wire โ‰ค 50m (shielded cable recommended).
โš ๏ธ RS485 Networking: Addresses must be unique when multiple devices are connected in parallel. For bus length >100m, connect 120ฮฉ termination resistors at both ends.

8. Troubleshooting

PhenomenonPossible CauseSolution
Channel displays -999โ„ƒPT100 not connected or broken wireCheck if PT100 wiring is loose or broken
Both channels show identical dataCross wiring or channel short circuitTest each channel separately by disconnecting one
Severe temperature fluctuationInterference, poor contactSwitch to 3-wire connection, add shielded cable
Large error in 3-wire modeCompensation wire incorrectly connectedCorrectly identify PT100 three wires (typically two red, one white)
No communicationAddress/baud rate mismatchCheck host parameters, or restore factory settings

9. Factory Reset

Short the two internal test pads (or DIP switch) and power cycle. Keep shorted for 5 seconds then disconnect. Device will restore to: Address 1, Baud Rate 9600, Celsius unit. Refer to internal silkscreen or contact manufacturer for specific pad locations.

10. Package Contents

11. Ordering Information

Model CodeChannelsPT100 TypeWiring MethodPower SupplyCommunication
YTL-PT100-2CH2PT100 (ฮฑ=0.00385)2-wire/3-wire selectable per channel5-9V DCRS485 MODBUS

Custom range (e.g., -200~600โ„ƒ) and higher accuracy versions available. Please contact manufacturer for details.

Manufacturer: Nanjing Yingtelong Electronic Technology Co., Ltd.    Technical Support: ydcman@163.com
Version: V2.0  |  Release Date: March 2025  |  Manufacturer reserves the right to interpret this manual.