HP 34970A manual Measurement Fundamentals

Chapter 8 Tutorial

Measurement Fundamentals

y	I bdM ys q °uysq””
”q xqwu uqsu y q sxq y °uqu y q
usyu” “4 dxu yq”	MWW °uqu u uqsu v
bdM q q”s”q yq”uuu4
I bdM xq u xywxuqry”yv °uqu qsu
dxu v q	bdM yu	bdM q w
sxysu v xywx3qssqsw3u° °uqu°uxu RZ 9:A=6I
bdM x	α E 64669>; .MSX 5 SNL =;7/ qt	α E 64669A74

“PT100” is a special label that is sometimes used to refer to an bdM with α = 0.00385 and R6 = 100Ω.

The resistance of an bdM is nominal at 0 °C and is referred to as R6. The HP 34970A can measure bdMs with R6 values from 49Ω to 2.1 kΩ.

You can measure bdMs using a 2-wire or 4-wire measurement method. The 4-wire method (with offset compensation) provides the most accurate way to measure small resistances. Connection lead resistance is automatically removed using the 4-wire method.

A thermistor is constructed of materials

that non-linearly changes resistance with changes in temperature. The internal MWW measures the resistance of the thermistor and then calculates the equivalent temperature.

Thermistors have a higher sensitivity than thermocouples or bdMs. 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 MWW supports

2.2 kΩ (44004), 5 kΩ (44007), and 10 kΩ (44006) thermistors.

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