Product category:
Temperature, pressure and flow measurement
News Release from: Betatherm Ireland | Subject: BetaLinear series
Edited by the Laboratorytalk Editorial
Team on 08 October 2003
Linearising NTC thermistors
In simple terms, a linear output makes it easier in terms of accommodating existing instrumentation and minimising computational software requirements
The principal benefit of NTC thermistors is the high level of sensitivity offered versus other sensor types (typical: -3% to -6% change in resistance per degree centigrade (C) However, the relationship between resistance and temperature is not linear
This article was originally published on Laboratorytalk on 23 Dec 2002 at 8.00am (UK)
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This non-linearity is not an issue in sensing applications where there is computing power available to use a mathematical model to relate the resistance of the NTC thermistor versus to its temperature.
In certain temperature sensing applications however, a linear response (of voltage or resistance) versus temperature is desirable.
In simple terms, a linear output makes it easier in terms of accommodating existing instrumentation and minimising computational software requirements.
Betatherm introduces the BetaLinear series of devices, a solution that maintain the advantages of the NTC thermistor (high sensitivity, small size and interchangeability) while offering a linear signal output.
The BetaLinear series device combine precision resistors and thermistors, which in combination generate a linear response to temperature.
The linear composite typically consists of two or three sensor elements; the most popular being (36K53A1) which uses two thermistor elements (30K5 and 6K3) and appropriate resistors which give a linear output in the range of 0-100C.
The circuit designs can accommodate a wide variety of circuit mounting options.
These include custom probes assemblies for the thermistor sensing elements and mounting precision resistors at board level in a control module.
It is also possible to package the thermistors and resistors which form the linearisation circuit in a single probe construction.
These linear thermistor networks are ideally suited for temperatures measurement and control in the range from -30C to +100C.
They are easily interfaced to both analog and digital circuitry.
The BetaLinear series can be configured in either resistance or voltage mode where they can provide up to ten times the voltage output of a thermocouple sensor.
Thermistor accuracy, depending upon construction, is +/-0.3C from 0C to 70C.
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