Temperature Measurements - Agilent Technologies 34420A User Manual

Chapter 7 Measurement Tutorial
Measurement Techniques and Sources of Error

Temperature Measurements

A temperature measurement is either a resistance measurement or a
voltage measurement, converted to a temperature mathematically inside
the meter. The mathematical conversions requires the knowledge of
specific properties of specific transducer types. The conversion routines
used are compatible with ITS-90. The conversion accuracy (not including
the transducer accuracy) for each transducer type is:
RTD 0.05° C
Thermistor 0.1° C
Thermocouple 0.2° C
Errors associated with temperature measurements include all those
listed for dc Voltage and Resistance Measurements. The largest source of
error in temperature measurements is the transducer itself.
Your measurement requirements determine which temperature
transducer type to use. Each transducer type has a particular
temperature range, accuracy, and cost. Each type of transducer is
described in more detail in the following subsections. The table below
summarizes some general specifications for each type of transducer.
Use the table to help select the general type of transducer to use;
transducer manufacturers can provide you with exact specifications
for a particular transducer.
Temperature Range
Measurement Type
Transducer
Sensitivity
Accuracy
Cost (approx) $20.00 to $100.00 ea*
Durability
*Estimated cost in U.S. Dollars
RTD
-200 to 850 C
°
4-wire Resistance 2-wire Resistance
R X 0.004 C
0
°
0.01 to 0.1 C
°
$10.00 to $100.00 ea*
Fragile
Thermistor Thermocouple
-80 to 150 C -210 to 1820
°
Voltage
400 / C 6 to 60
W °
0.1 to 1 C 0.5 to 5
°
$1.00/foot*
Fragile Rugged
C
°
V/ C
°
C
°
7
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