UltimaSerial Verify the accuracy of DI-245 USB Data Acquisition System

Windaq add-ons

 


 


 


 

We have a real application to use the Lab Note Taker addon. It was used to verify the accuracy of a DI-245 four-channel voltage and thermocouple data logger. The result can be found below.

What are involved 

Fluke 515A Temperature/Pressure Calibrator, which is connected to the WinDaq-running PC via either a real COMM port or USB-based virtual COMM port.

DI-245 four-channel voltage and thermocouple data logger

Noble metal thermocouple wires from Omega include

SPPL (Platinum)

SP10RH (Platinum 10% Rhodium)

SP13RH (Platinum 13% Rhodium)

SP6RH (Platinum 6% Rhodium)

SP30RH (Platinum 30% Rhodium)

To construct S,B,R type thermocouples:

  • Type S: Platinum (-) vs Platinum 10% Rhodum (+)

  • Type R: Platinum (-) vs Platinum 13% Rhodum (+)

  • Type B: Platinum 6% Rhodum (-) vs Platinum 30% Rhodum (+)

N and E type thermocouple wires from Omega

  • Type N: TT-N-20-SLE

  • Type E: GG-E-24

Generic J, K and T thermocouple wires

Environment chamber for thermo-stability test

WinDaq acquisition software

Lab Note Taker addon

Configuration:

Maximum WinDaq sample rate is set to 200s/s

WinDaq Sample rate is set to 40s/s, average is turned on

Ambient temperature: 25C except the study of thermal offset drift inside the environment chamber

Minimum air flow

Sample script file for Lab Note Taker 

TC_TYPE E<SKIP>
OPER<SKIP>
4<INTERVAL><SKIP>
OUT -160 CEL 
OUT -150 CEL
OUT -140 CEL
OUT -130 CEL
OUT -120 CEL
OUT -110 CEL
OUT -100 CEL
OUT -90 CEL
....
OUT 880 CEL
OUT 890 CEL
OUT 900 CEL
OUT 910 CEL
OUT 920 CEL
OUT 930 CEL
OUT 940 CEL
OUT 950 CEL
OUT 960 CEL
OUT 970 CEL
OUT 980 CEL
OUT 990 CEL

Test Results

Voltage accuracy for all gains, single channel

  • Full test result in Excel spreadsheet

  • Range Max Error Accuracy
    50V 19mV 0.018%
    25V 5mV 0.010%
    10V 2.3mV 0.012%
    5V 1.4mV 0.014%
    2.5V 0.6mV 0.012%
    1V 171uV 0.09%
    0.5V 137uV 0.014%
    250mV 60uV 0.012%
    100mV 17uV 0.09%
    50mV 13uV 0.013%
    25mV 7uV 0.014%
    10mV 15uV 0.026% + 10uV

All ranges are well within the spec of 0.05%+10uV

Offset thermal drift, from 25C to 55C, channel shorted, range is set to 10mV

The offset was within 10uV throughout the temperature range

Test result in WinDaq file format

DI-245 offset thermal drift test

Thermocouple accuracy for all TC types, single channel 

All TC measurements are well within the published spec

Thermocouple accuracy for all four channels, type E

The readings are well within the spec of 0.1% of span + 1

Thermocouple accuracy with and without Open-Thermocouple-Detection (OTD) option

DI-245 employs Open-Thermocouple-Detection, or TC Burnout Test,  feature when thermocouple inputs are selected, and it helps to monitor the thermocouple connection, but this feature will affect the readings, especially in type SBR.

DI-245 Open-Thermocouple-Detection (OTC), or Thermocouple Burnout Test

To demonstrate the difference, we conducted an accuracy test on a standard DI-245, using S-type thermocouple on all four channels, then OTD is removed and a comparison test was conducted to show the difference

  • Full test result in Excel spreadsheet
     

  • Here is the side-by-side comparison of accuracy plotting with and without OTD, and you can see when OTD is removed, the reading is much much better

Conclusion, if very accurate temperature measurement is required, contact DATAQ on how to remove the OTC circuit

 

Last update: 03/06/15

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