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Four Channel Temperature Alarm - doc00032

Description :

The temperature in a pipe is monitored with four RTD Pt-100 Sensors, The type of probe could be Extruder RTD probes with Bayonet or Compression Fitting, Get it from  Omega. To keep costs low you can choose small thin film RTD sensors, they will be fast but on rough usage may break.

See another Solution that is about - Temperature Meters with Analog Recorder Output

The temperature at four points are measured by Temperature Module and compared with one common setpoint 0-200 deg F, an alarm output  LED out-a goes ON when the measured temperature exceeds the common setpoint.

The Source design files for this project are here - Four Channel Temperature Alarm Docs

                        Channel Temperature Alarm

The time taken to measure the temperature at the 4 points will be less than 4 seconds. An optional  display of the measured temperature as shown above can be avoided by using a DMM to adjust the setpoint.

The Analog Timer Module can be set from 0- 30 minutes.  If out-a  remains high even after set time a out-b alarm goes on to sound a buzzer and flash a LED light.

A digital timer is avoided so as to keep costs low, The alarm is audio-visual, piezo electric buzzer for sound and a flashing red big 10mm LED for visual annunciation, a digital output is also given to turn on an optional SSR to power a hooter or to turn off something.

Whenever out-a goes high and low the Counter Module counts from 0000 to 9999. The counter can be reset at any time by pressing a button. This will count the number of times temperature in pipe went above the setpoint.

The unit is powered by a 9V battery to backup the counts in counter module, The LED displays are turned on by a pushbutton for momentary use to extend battery life. 

Resources :

Watlow heating elements, industrial heaters.
Watlow is the largest custom designer and manufacturer of industrial electric heaters, sensors and controllers

NPL Beginners Guides to Measurement - Temperature
The accurate measurement of temperature is vital across a broad spectrum of human activities, including industrial processes (e.g. making steel), manufacturing; monitoring and in health and safety.