acquire temperature data from an rtd -凯发k8网页登录

this example shows how to acquire temperature data from a resistive temperature device (rtd) and display the readings. the device is attached inside a pc case to monitor the internal temperature changes.

discover devices that support rtds

to discover a device that supports bridge sensor measurements, access the device in the table returned by the daqlist command. this example uses an ni 9219 module in national instruments® compactdaq chassis ni cdaq-9178. this is a 24-bit universal analog input module and is module 7 in the chassis.

d = daqlist("ni")

d =
  12×4 table
     deviceid                 description                    model             deviceinfo     
    ___________    __________________________________    _____________    ____________________
    "cdaq1mod1"    "national instruments ni 9205"        "ni 9205"        [1×1 daq.deviceinfo]
    "cdaq1mod2"    "national instruments ni 9263"        "ni 9263"        [1×1 daq.deviceinfo]
    "cdaq1mod3"    "national instruments ni 9234"        "ni 9234"        [1×1 daq.deviceinfo]
    "cdaq1mod4"    "national instruments ni 9201"        "ni 9201"        [1×1 daq.deviceinfo]
    "cdaq1mod5"    "national instruments ni 9402"        "ni 9402"        [1×1 daq.deviceinfo]
    "cdaq1mod6"    "national instruments ni 9213"        "ni 9213"        [1×1 daq.deviceinfo]
    "cdaq1mod7"    "national instruments ni 9219"        "ni 9219"        [1×1 daq.deviceinfo]
    "cdaq1mod8"    "national instruments ni 9265"        "ni 9265"        [1×1 daq.deviceinfo]
    "dev1"         "national instruments pcie-6363"      "pcie-6363"      [1×1 daq.deviceinfo]
    "dev2"         "national instruments ni elvis ii"    "ni elvis ii"    [1×1 daq.deviceinfo]
    "dev3"         "national instruments pcie-6363"      "pcie-6363"      [1×1 daq.deviceinfo]
    "dev4"         "national instruments pcie-6363"      "pcie-6363"      [1×1 daq.deviceinfo]

deviceinfo = d{7, "deviceinfo"}

deviceinfo = 
ni: national instruments ni 9219 (device id: 'cdaq1mod7')
   analog input supports:
      9 ranges supported
      rates from 0.1 to 100.0 scans/sec
      4 channels ('ai0','ai1','ai2','ai3')
      'voltage','current','thermocouple','rtd','bridge' measurement types
   
this module is in slot 7 of the 'cdaq-9178' chassis with the name 'cdaq1'.

add an rtd channel

create a dataacquisition, and add an analog input channel with rtd measurement type.

dq = daq("ni");
dq.rate = 30;
ch = addinput(dq, "cdaq1mod7", "ai3", "rtd");

set sensor properties

refer to the sensor data sheet and match the values accordingly. in this example, an sa1-rtd series sensor from omega® is used. set units to "fahrenheit", rtd type to "pt3851", configure the rtd circuit as "fourwire", and set the resistance to 100 ohms.

ch.units = "fahrenheit";
ch.rtdtype = "pt3851";
ch.rtdconfiguration = "fourwire";
ch.r0 = 100;

set adctimingmode

by default, the adc timing mode adctimingmode of the channel is set to "highresolution". set the adctimingmode to "highspeed".

ch.adctimingmode = "highspeed";

acquire and plot data

use the read command to acquire data.

data = read(dq, seconds(1));
plot(data.time, data.cdaq1mod7_ai3);
degreesign = 176;
ylabel(sprintf("temperature (�)", degreesign));