Temperature Measurements

NI Digital Multimeters

previous page next page

Temperature Measurements

The NI 4065/4070/4071/4072 can measure temperature using common temperature transducers. The three most commonly used transducers for temperature are thermocouples, resistance temperature detectors (RTDs), and thermistors. Compatible thermocouples and RTDs are available from National Instruments and compatible thermistors are available from Omega.

The following table illustrates some of the capabilities and limitations of these sensors. Use this table as a reference for choosing the right sensor for your temperature measurement application.

Sensor Advantages Disadvantages
Thermocouples wide range, fast response,
inexpensive
require reference temperature,
nonlinear
RTDs rugged, accurate slow response, lead resistance,
nonlinear, self-heating
Thermistors repeatable, fine resolution,
low current, fast response		 narrow range,
nonlinear

The following table lists NI-DMM supported device/sensor combinations:

Device Thermocouple Support RTD Support Thermistor Support
NI 4070/4071/4072/4065
  • 2-wire
  • ITS-90 polynomial scaling
  • Presets for types J, K, N, T, E, R, S, and B
  • 4-wire and 2-wire
  • Callendar-Van Dusen scaling
  • Presets for common sensor standards (alpha=0.00385, alpha=0.00391, etc.)
  • Custom coefficients
  • 2-wire
  • Stein-Hart scaling
  • Presets for common Omega 44000 Series thermistors (44004, 44006, 44007)
  • Custom coefficients

Measurement Range, Resolution, and Options

NI-DMMs perform a measurement appropriate to the temperature transducer type (DC voltage for thermocouples, resistance for RTDs or thermistors), and convert this reading into degrees Celsius. See thermocouples, RTDs, and thermistors for specific cabling details.

When configuring a temperature transducer measurement, the user must specify the range and resolution of the underlying voltage or resistance measurement while configuring the DMM. The following range settings are recommended for optimal accuracy, speed, and range of the supported transducers. Users may wish to select a different range for measurements at extreme temperatures or when using custom transducer types.

Transducer Recommended Range
Thermocouple 100 mV
100 Ω RTD 1 kΩ
1k Ω RTD 10 kΩ
1kΩ to 10kΩ Thermistor 100 kΩ

Other measurement options, such as Auto Zero, Offset Compensated Ohms, Settling Time, and Aperture Time still apply to the underlying voltage or resistance measurement where applicable.

previous page start next page