Tehama Wireless Design Group TWS 049 Users Manual

Tehama Wireless Design Group 11/14/2005

TempSens User Guide

General Description

The TempSens system consists of three device types to remotely monitor temperature readings
and provide the data to a PC for formal presentation and reporting. Sensor devices will be
placed in all locations requiring local monitoring of temperature. The Sensors will transmit time
stamped temperature data to the single Base device in the system, which receives the data and
forwards it to the host PC via a USB interface. For sensors that are out of range from the base,
Repeater devices can be added in appropriate locations to relay the data between sensors and
the base.

The system will operate in the 865MHz (Europe/Asia) and 915Mhz (US) ISM bands using off the
shelf FSK RFIC radios. The system will operate over 60 narrow band frequency channels with
a baud rate of 4800bps, incorporating a bidirectional communication link with Acknowledge
(ACK) messages to ensure all data reaches the base. The sensors are battery operated,
bursting data packets at pre-programmed times then shutting down to conserve battery life,
estimated to exceed 2 years. The repeaters will be line powered, while the base unit will be
powered via line or USB interface used to communicate with the PC.

With an average sensor transmission rate of four per hour, a single Base can accommodate
many sensors. Through the use the ACK messages and local memory in both the sensors and
repeaters (to store transmitted data that has not been confirmed as received by the base via an
ACK message), the number of sensors supported can approach the theoretical maximum.
There is no limit to the number of repeaters, though an average installation may require 1
repeater for every 10-15 sensors.

Sensor Sensor

Sensor

Sensor

Sensor

Base

Sensor

Sensor

iMac

Repeater

Sensor

Sensor

Sensor

Sensor

Repeater

Repeater

Sensor

Sensor

Sensor

Sensor

SensorSensorSensor

Figure 1: Typical System

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Tehama Wireless Design Group 11/14/2005

INTERFERENCE CAUSED BY UNAUTHORIZED MODIFICATIONS TO THIS EQUIPMENT.

A system consists of two or three types of hardware, and two pieces of software:

• PC Database Software

• Tehama Configuration Utility

• One Base Unit with USB cable

• A variable number of Sensors radios, each with 2 AA batteries

• A variable number of Repeater radios (optional, depending on size of installation) with

external DC power supply

Warning

NOTE: THE MANUFACTURER IS NOT RESPONSIBLE FOR ANY RADIO OR TV
SUCH MODIFICATIONS COULD VOID THE USER’S AUTHORITY TO OPERATE THE

EQUIPMENT

Tehama Configuration Utility

The following discussion assumes the base is connected a PC via the USB cable, and both the
PC Database Software and the Tehama Configuration Utility are installed.

This utility can be run on the PC either prior to or during a site installation, or when new sensors
are added to a system. All sensors come from the factory with a default configuration, and the
utility need not be run if no sensors are required to deviate from the default.

The Utility will allow the following options to be configured on a sensor:

• Transmit Interval, defined as the time between scheduled transmissions of temperature
data. A temperature measurement is taken every Transmit Interval, and the data
transmitted within 60 seconds after the measurement. The units for this parameter are
seconds, and the default value is 900 seconds (15 minutes).

• Measure Interval, defined as the time between scheduled temperature measurements.
This is used in conjunction with Temperature Change (see below) and must be smaller
than the Transmit Interval time. A value of 0 for this parameter will disable
measurements in between the Transmit Interval. The units for this parameter are in
seconds, with default set to 0.

• Temperature Change, defined as a percentage change in the Thermistor resistance
value (i.e. temperature) detected by the sensor. A Delta Temp alarm will be generated
within the PC Software if a Sensor reading taken at a Measure Interval is more than
Temperature Change percent from the prior Transmit Interval value. The units for this
parameter are Percent (%), with the default value set to 0.

No other parameters are configurable on the sensors. Absolutely no parameters are
configurable on the Base or Receiver.

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