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Your measurement requirements will help you to determine which temperature transducer type to use. Each
transducer type has a particular temperature range, accuracy, and cost. The table below summarizes some typical
specifications for each transducer type. Use this information to help select the transducer for your application. The
transducer manufacturers can provide you with exact specifications for a particular transducer.
Parameter
Temperature Range
Measurement Type
Transducer Sensitivity
Probe Accuracy
Cost (U.S. Dollars)
Durability
RTD measurements
An RTD is constructed of a metal (typically platinum) that changes resistance with a change in temperature in a
precisely known way. The internal DMM measures the resistance of the RTD and then calculates the equivalent
temperature.
An RTD has the highest stability of the temperature transducers. The output from an RTD is also very linear. This
makes an RTD a good choice for high-accuracy and long-term measurements. The DAQ970A/DAQ973A supports
RTDs with α = 0.00385 (DIN / IEC 751) using ITS-90 software conversions. "PT100" is a special label that is
sometimes used to refer to an RTD with α = 0.00385 and R0 = 100 Ω.
The resistance of an RTD is nominal at 0 °C and is referred to as R0. The DAQ970A/DAQ973A can measure RTDs with
R0 values from 100 Ω ±1% or 1000 Ω ±1%.
You can measure RTDs using a 2-wire or 4-wire measurement method. The 4-wire method provides the most
accurate way to measure small resistances. Connection lead resistance is automatically removed using the 4-wire
method.
Thermistor measurements
A thermistor is constructed of materials that non-linearly changes resistance with changes in temperature. The
internal DMM measures the resistance of the thermistor and then calculates the equivalent temperature.
Thermistors have a higher sensitivity than thermocouples or RTDs. This makes a thermistor a good choice when
measuring very small changes in temperature. Thermistors are, however, very non-linear, especially at high
temperatures and function best below 100 °C.
Because of their high resistance, thermistors can be measured using a 2-wire measurement method. The internal
DMM supports 2.2 kΩ (44004), 5 kΩ (44007), and 10 kΩ (44006) thermistors. The thermistor conversion routines
used by the DAQ970A/DAQ973A are compatible with the International Temperature Scale of 1990 (ITS-90).
Keysight DAQ970A/DAQ973A User's Guide
Thermocouple
-210 °C to 1820 °C
Voltage
6 μV/°C to 60 μV/°C
0.5 °C to 5 °C
$1/foot
Rugged
RTD
-200 °C to 850 °C
2- or 4- Wire Ohms
≈ R0 × 0.004 °C
0.01 °C to 0.1 °C
$20 to $100 each
Fragile
4 Measurement Tutorials
Thermistor
-80 °C to 150 °C
2- or 4- Wire Ohms
≈ 400 Ω/°C
0.1 °C to 1 °C
$10 to $100 each
Fragile
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