# Creating Virtual Channels for RTDs in NI-DAQmx and Traditional NI-DAQ

Updated Jun 29, 2018

• PXIe-4357

• NI-DAQmx

## Issue Details

How do I create a virtual channel in Measurement & Automation Explorer (MAX) for my RTD using NI-DAQmx, and how is it different from a Traditional NI-DAQ virtual channel?

## Solution

In Traditional NI-DAQ, the scaling is set when you select the RTD Standard you are using. In NI-DAQmx, the RTD-defining characteristics are used to set the scaling instead. This removes confusion about multiple names for the same RTD type. The table below lists the RTD types available in NI-DAQmx. This list is also included in the NI-DAQmx Help located at: Start»Programs»National Instruments»NI-DAQ.

 Standards Material TCR Typical Ro (Ohms) Callendar-Van Dusen Coefficient Notes IEC-751 DIN 43760  BS 1904  ASTM-E1137  EN-60751 IEC-60751* Platinum 3851 100  1000 A = 3.9083 x 10-3  B = -5.775 x 10-7  C = 4.183 x 10-12 Most common RTDs including Pt100 Low-cost vendor compliant RTD** Platinum 3750 1000 A = 3.81 x 10-3  B = -5.870 x 10-7 C = -4.4 x 10-12 Low-cost RTD JISC 1604 Platinum 3916 100 A = 3.9739 x 10-3 B = -5.870 x 10-7  C = -4.4 x 10-12 Used primarily in Japan US Industrial Standard D-100 American Platinum 3920 100 A = 3.987 x 10-3 B = -5.8686 x 10-7  C= -4.167 x 10-12 Low-cost RTD US Industrial Standard American Platinum 3911 100 A = 3.962 x 10-3 B = -5.8495 x 10-7  C= -4.233 x 10-12 Low-cost RTD ITS-90 Platinum 3928 100 A = 3.9888 x 10-3 B = -5.915 x 10-7  C= -3.85 x 10-12 The definition of temperature
*EN-60751 and IEC-60751 are international equivalent standards.
**No standard. Check the TCR.

In NI-DAQmx, instead of choosing between four standards for the RTD type as in Traditional NI-DAQ, you can choose the actual RTD type, such as Pt 3750. You also can select the external wiring configuration—2-wire, 3-wire, or 4-wire. Selecting the nominal resistance value (Ro), excitation current source, and excitation value is the same as in Traditional NI-DAQ.

If you do not want to use a virtual channel or task, there is a built-in LabVIEW VI for scaling instead—the Convert RTD Reading VI located on the Signal Conditioning palette.