--- title: "ComWinTop CWT-TM-8PT" description: "Read 8 PT100/PT1000 temperature channels via Modbus RTU. DIN-rail module with RS-485, -180 to +650 °C range, 0.25 °C accuracy. TapHome integration template." url: "https://taphome.com/en/compatibility/comwintop-8-channels-pt100-pt1000/" language: en lastmod: 2026-03-31 generator: hugo ai: topics: ["modbus-rtu","sensor","rs485","temperature","din-rail","pt100","pt1000"] questions: ["How to integrate ComWinTop CWT-TM-8PT with TapHome?","What does the ComWinTop 8-channel temperature sensor TapHome template read?","How to connect ComWinTop PT100/PT1000 module via RS-485 to TapHome?","How to change the Modbus slave ID on a ComWinTop CWT-TM-8PT module?","What is the difference between PT100 and PT1000 variants of ComWinTop CWT-TM-8PT?"] --- # ComWinTop CWT-TM-8PT Communication: Modbus RTU - [ComWinTop Store — CWT-TM-8PT](https://store.comwintop.com/products/8-channels-pt100-pt1000-rs485-modbus-output-temperature-acquisition-module) ## Integration guide The ComWinTop CWT-TM-8PT is a DIN-rail mounted temperature acquisition module available in two variants — CWT-TM-8PT100 (for PT100 sensors) and CWT-TM-8PT1000 (for PT1000 sensors). It reads up to 8 temperature channels and exposes them over Modbus RTU via RS-485. TapHome polls all 8 channels as individual temperature sensors with a 15-second update interval. ## Hardware connection ### Technical specifications | Parameter | Value | |-----------|-------| | Power supply | DC 8–30 V | | Sensor type | PT100 or PT1000 (depending on model) | | Measurement range | -180 °C to +650 °C | | Resolution | 0.1 °C | | Accuracy | 0.25 °C | | Sensor connections | 2-wire and 3-wire | | Output | RS-485 (Modbus RTU), isolated | | Operating temperature | -30 °C to +55 °C | | Mounting | 35 mm DIN rail | | Dimensions | 88 x 72 x 59 mm | ### RS-485 wiring Connect the module to the TapHome Modbus RTU Gateway using a 3-wire RS-485 connection: - **A (D+)** → A+/D+ on TapHome RS-485 - **B (D-)** → B-/D- on TapHome RS-485 - **GND** → GND on TapHome power supply ### Sensor wiring Each channel has three terminals: **RTDx+**, **RTDx-**, and **GND**. **Three-wire connection (recommended):** - RTDx+ → sensor wire 1 - RTDx- → sensor wire 2 - GND → sensor wire 3 (compensation wire) Three-wire wiring compensates for lead wire resistance and provides better accuracy. **Two-wire connection:** - RTDx+ → sensor wire 1 - RTDx- → sensor wire 2 - **Short RTDx- and GND together** for each two-wire channel > [!WARNING] > For two-wire connections, the RTDx- and GND terminals **must** be shorted together. Without this jumper, the measurement will be inaccurate due to uncompensated lead resistance. ## Configuration The module ships with default communication parameters that match the TapHome template — no configuration is needed for a single-module setup. ### Default parameters | Parameter | Default value | |-----------|---------------| | Baud rate | 9600 | | Data bits | 8 | | Parity | None | | Stop bits | 1 | | Slave ID | 1 | ### Changing the slave ID When connecting multiple modules on the same RS-485 bus, each module must have a unique slave address. The slave ID is stored in holding register 0x10 (high byte) and can be changed via a Modbus write command (function code 06H). The valid range is 1–250. After changing the slave ID, update the **Slave Id** import parameter in TapHome to match the new address. ### Changing baud rate and parity Baud rate and parity are stored in register 0x10 (low byte). Supported baud rates: 1200, 2400, 4800, 9600 (default), 14400, 19200. Parity options: None (default), Even, Odd. > [!TIP] > The module exposes three service attributes in TapHome — **Slave ID**, **Speed**, and **Parity** — so you can verify the current communication parameters directly from the TapHome interface without additional tools. ## Device capabilities ### Temperature channels The template provides 8 independent temperature sensors, one per channel. Each sensor reads its value from a dedicated Float register (IEEE 754, 4 bytes) over Modbus RTU. The readings are direct °C values — no conversion or scaling is required. | Channel | Register | Sensor | |---------|----------|--------| | 1 | H:0x30 | Temperature Sensor (1) | | 2 | H:0x32 | Temperature Sensor (2) | | 3 | H:0x34 | Temperature Sensor (3) | | 4 | H:0x36 | Temperature Sensor (4) | | 5 | H:0x38 | Temperature Sensor (5) | | 6 | H:0x3A | Temperature Sensor (6) | | 7 | H:0x3C | Temperature Sensor (7) | | 8 | H:0x3E | Temperature Sensor (8) | All channels are read-only and polled every 15 seconds. Unused channels (with no sensor connected) will report a fault value — the module supports disconnection and short-circuit detection on sensor inputs. ### Additional capabilities The module also provides an alternative UINT register set (H:0x68–H:0x6F) with 2-byte integers and 0.1 °C resolution. The TapHome template uses the Float format for higher precision. Both formats read the same physical sensors — the UINT registers can be used as a lightweight alternative if needed in a future template update. ## Troubleshooting ### No temperature readings 1. Verify the RS-485 wiring — A (D+) and B (D-) must not be swapped 2. Check that the slave ID in TapHome matches the module configuration (default: 1) 3. Confirm baud rate 9600, parity None, 1 stop bit in TapHome gateway settings 4. Ensure the module is powered (DC 8–30 V) ### Inaccurate readings 1. For two-wire connections, verify that RTDx- and GND are shorted together on each channel 2. Consider switching to three-wire sensor connections for better accuracy 3. Check for long cable runs — lead wire resistance affects two-wire measurements ### Sensor fault reported 1. Check the physical connection between the sensor and the module terminal 2. Verify the sensor type matches the module variant (PT100 sensor with CWT-TM-8PT100, PT1000 with CWT-TM-8PT1000) 3. The module detects both disconnection and short-circuit conditions on sensor inputs ## Available devices 8 These devices appear in TapHome after import. ComWinTop 8-Channel PT100/PT1000 Module Service Attributes | | | |----------|-----------------------------------------------------------------------------| | Slave ID | | | Speed | Communication baud rate — 9600 (default), 1200, 2400, 4800, 14400, or 19200 | | Parity | Serial parity setting — None (default), Even, or Odd | Service Attributes Slave ID ```taphome getbyte(modbusr(H, 0x10, Uint16), 1) ``` Speed ```taphome var ret := getbyte(modbusr(H, 0x10, Uint16), 0); switch(getbits(ret, 0, 3), 0, "9600 (default)", 1, "1200", 2, "2400", 3, "4800", 4, "9600", 5, "14400", 6, "19200", "unknown"); ``` Parity ```taphome var ret := getbyte(modbusr(H, 0x10, Uint16), 0); switch(getbits(ret, 3, 2), 0, "None", 1, "Even", 2, "Odd", "Odd"); ``` Temperature Sensor (1) Temperature Sensor Read-only Register: H:0x30 Float Unit: °C IEEE 754 float Read temperature ```taphome MODBUSR(H, 0x30, float) ``` Temperature Sensor (2) Temperature Sensor Read-only Register: H:0x32 Float Unit: °C IEEE 754 float Read temperature ```taphome MODBUSR(H, 0x32, Float) ``` Temperature Sensor (3) Temperature Sensor Read-only Register: H:0x34 Float Unit: °C IEEE 754 float Read temperature ```taphome MODBUSR(H, 0x34, Float) ``` Temperature Sensor (4) Temperature Sensor Read-only Register: H:0x36 Float Unit: °C IEEE 754 float Read temperature ```taphome MODBUSR(H, 0x36, Float) ``` Temperature Sensor (5) Temperature Sensor Read-only Register: H:0x38 Float Unit: °C IEEE 754 float Read temperature ```taphome MODBUSR(H, 0x38, Float) ``` Temperature Sensor (6) Temperature Sensor Read-only Register: H:0x3A Float Unit: °C IEEE 754 float Read temperature ```taphome MODBUSR(H, 0x3A, Float) ``` Temperature Sensor (7) Temperature Sensor Read-only Register: H:0x3C Float Unit: °C IEEE 754 float Read temperature ```taphome MODBUSR(H, 0x3C, Float) ``` Temperature Sensor (8) Temperature Sensor Read-only Register: H:0x3E Float Unit: °C IEEE 754 float Read temperature ```taphome MODBUSR(H, 0x3E, Float) ``` **Connection:** Modbus RTU • 9600 baud• 8N1 • Slave ID: $\[SlaveId] Possible improvements (8) - H:0x68 Channel 1 Temperature (UINT) — Alternative UINT format (2 bytes, scale 0.1). Template uses Float format (0x30) instead — both read the same physical sensor - H:0x69 Channel 2 Temperature (UINT) — Alternative UINT format (2 bytes, scale 0.1). Template uses Float format (0x32) instead - H:0x6A Channel 3 Temperature (UINT) — Alternative UINT format (2 bytes, scale 0.1). Template uses Float format (0x34) instead - H:0x6B Channel 4 Temperature (UINT) — Alternative UINT format (2 bytes, scale 0.1). Template uses Float format (0x36) instead - H:0x6C Channel 5 Temperature (UINT) — Alternative UINT format (2 bytes, scale 0.1). Template uses Float format (0x38) instead - H:0x6D Channel 6 Temperature (UINT) — Alternative UINT format (2 bytes, scale 0.1). Template uses Float format (0x3A) instead - H:0x6E Channel 7 Temperature (UINT) — Alternative UINT format (2 bytes, scale 0.1). Template uses Float format (0x3C) instead - H:0x6F Channel 8 Temperature (UINT) — Alternative UINT format (2 bytes, scale 0.1). Template uses Float format (0x3E) instead ## Import parameters Enter these values when you import the XML. | Asked in the app | Default | |------------------|---------------| | Slave Id | `1` | | IP address | `192.168.1.0` | ## Sources - ComWinTop Store — CWT-TM-8PT Product Page (Specs, Register Map, Wiring) [store.comwintop.com](https://store.comwintop.com/products/8-channels-pt100-pt1000-rs485-modbus-output-temperature-acquisition-module) 2026-03-31 - Home Assistant Community — ComWinTop Modbus RTU Configuration [community.home-assistant.io](https://community.home-assistant.io/t/config-for-rtu-modbus-temperature-sensor/732447) 2026-03-31 ## Related Documentation - [Modbus Integration](https://taphome.com/en/compatibility/modbus-guide/) - [Modbus](https://taphome.com/en/docs/integration/modbus/) - [Simple configuration using templates](https://taphome.com/en/docs/integration/modbus/templates/) - [Modbus scripts and prefetch](https://taphome.com/en/docs/script/modbus-scripts/) - [Modbus functions](https://taphome.com/en/docs/script/modbus/) - [Modbus data types](https://taphome.com/en/docs/script/modbus-data-types/)