Two Wire Multi Sensor- Installation & Initial Setup

| Overview

The Multi Sensor is a sensor designed to make the 75F VAV application Title 24 Compliant. This sensor can be used to sense temperature, Humidity, CO2, and occupancy, adding IAQ and Occupancy control to your application. 

The two-wire Multi Sensor is an advanced version of the one-wire Multi Sensor. It is a part of the two-wire, Power Over RS485 (POR) platform. 

It uses a two-wire POR power and communication.   

For information on one wire interface Multi Sensor, refer to OWI Multi Sensor - Installation & Initial Set Up

| Two-Wire Multi Sensor Installation & Wiring

| Precautions

• Only use with 75F sensor applications
• Only use certified 75F sensor bus cables for connecting the sensor to 75F devices.
• Do not install in direct sunlight or above direct heat or cool sources to avoid variance
• Install according to all state and local codes.

| Mounting

It is easily mounted on a wall by self-tapping screws.

The following steps need to be used to achieve an effective installation.

• Drill a hole of diameter 25mm.
• Mount the Multi Sensor grommet using two self-tapping screws (provided in the box)
• Make sure the level lines on the gromet are parallel to the floor.

Similarly, the Multi Sensor can be mounted using a toggle bolt grommet as below:

| Detaching the Multi-Sensor

As shown below, the installed Multi Sensor can be detached from the grommets, using a Philip head Screwdriver.

With its daisy-chaining capability, the Multi-Sensor uses a two-wire adapter to connect more devices in the bus.

For more information on Daisy Chaining, refer to Daisy Chaining Capabilities of Sensors         

| More Information

When the top cover is removed, the Multi Sensor provides the user with additional capabilities.

• Press the Button to Set the Master Device to Pairing Mode, without accessing the device installed at the plenum in the building (press the button somewhere between 4 to 8 seconds).
• Press the Reset Button to reset the sensor.
• Use the Address Setting Switch to set the address for the sensor when more than one Multi Sensor is installed in a bus.
• Use the Switch to Set Device as  Daisy Chain/ End of Bus Device to set the sensor either as a daisy-chained device or the terminal device in the bus.

Example:

If 4 devices are on a bus, the first 3 will have the switch set to YES. And only for the last device the switch is set to NO.

Significance of Daisy Chain Switch         `

Transmission line effects often present a problem in data communication networks. These problems include reflections and signal attenuation.

A voltage applied or a signal sent from one end of the transmission line and received at the other are not the same at times. The effect and the resultant signal/voltage received are determined by the series resistances in line, the voltage applied, and the termination used.  

To avoid these signal reflections termination resistance must be fitted on each end of the main cable. The end resistance must be used only at the ends of the main cable.

The daisy chain switch in the sensor set to "NO" acts as the termination resistance for the network it is used in.                    

Note:  If the total length of the main cable is less than 50 m termination resistances can be avoided at the ends of the main cable.