TEMPERATURE DETECTION CIRCUITRYTemperature DetectorsSummaryTemperature detection circuit operation is summarized below.Circuit Operation SummaryThe basic bridge circuit consists of:- Two known resistors (R1 and R2) that are used for ratioing the adjustableand known resistances- One known variable resistor (R3) that is used to match the unknownvariable resistor- One unknown resistor (Rx) that is used to measure temperature- A sensing ammeter that indicates the current flow through the bridgecircuitThe bridge circuit is considered balanced when the sensing ammeter reads zerocurrent.A basic temperature instrument is comprised of:- An RTD for measuring the temperature- A bridge network for converting resistance to voltage- A DC to AC voltage converter to supply an amplifiable AC signal to theamplifier- An AC signal amplifier to amplify the AC signal to a usable level- A balancing motor/mechanical linkage assembly to balance the circuit’sresistanceAn open circuit in a temperature instrument is indicated by a very hightemperature. A short circuit in a temperature instrument is indicated by a verylow temperature.Temperature instrument ambient temperature compensation is accomplished by:- Measuring circuit resistor selection- Electronic circuitry design- Use of three or four wire RTD circuitsIC-01 Page 16 Rev. 0
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business