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INSTRUMENTATION AND CONTROL Module 2 Pressure Detectors |
TEMPERATURE DETECTION CIRCUITRY
Temperature Detectors
Summary
Temperature detection circuit operation is summarized below.
Circuit Operation Summary
The basic bridge circuit consists of:
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Two known resistors (R1 and R2) that are used for ratioing the adjustable
and known resistances
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One known variable resistor (R3) that is used to match the unknown
variable resistor
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One unknown resistor (Rx) that is used to measure temperature
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A sensing ammeter that indicates the current flow through the bridge
circuit
The bridge circuit is considered balanced when the sensing ammeter reads zero
current.
A basic temperature instrument is comprised of:
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An RTD for measuring the temperature
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A bridge network for converting resistance to voltage
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A DC to AC voltage converter to supply an amplifiable AC signal to the
amplifier
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An AC signal amplifier to amplify the AC signal to a usable level
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A balancing motor/mechanical linkage assembly to balance the circuit’s
resistance
An open circuit in a temperature instrument is indicated by a very high
temperature. A short circuit in a temperature instrument is indicated by a very
low temperature.
Temperature instrument ambient temperature compensation is accomplished by:
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Measuring circuit resistor selection
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Electronic circuitry design
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Use of three or four wire RTD circuits
IC-01
Page 16
Rev. 0
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